Antihypertensive Medications

Mechanism of Action

Thiazide and Thiazide-Like Diuretics

Thiazide diuretics inhibit the electroneutral sodium-chloride cotransporter (NCC), encoded by the SLC12A3 gene, on the apical membrane of the distal convoluted tubule. NCC reabsorbs approximately 5% to 10% of filtered sodium chloride. Structural studies have demonstrated that thiazide molecules (eg, hydrochlorothiazide, chlorthalidone, and indapamide) bind to an orthosteric site within the NCC ion-translocation pathway, competing with chloride for binding and preventing the conformational transition from the outward-facing to the inward-facing state, thereby arresting the transport cycle.[42] 

The blood pressure–lowering mechanism of thiazides is biphasic. In the acute phase (first 4-6 weeks), natriuresis reduces extracellular fluid volume and cardiac output, thereby activating compensatory neurohormonal responses, including the renin-angiotensin-aldosterone system and the sympathetic nervous system. During chronic therapy (beyond 6-8 weeks), intravascular volume normalizes via reverse autoregulation while blood pressure remains controlled through a sustained reduction in total peripheral vascular resistance.[43] This chronic vasodilatory effect occurs via multiple extrarenal mechanisms: activation of calcium-activated potassium channels in vascular smooth muscle, which increases open-state probability and causes membrane hyperpolarization; inhibition of the Rho/Rho-kinase signaling pathway, which reduces calcium sensitization in vascular smooth muscle cells independently of endothelial function; and possible improvement in endothelial nitric oxide bioavailability.[43][44] These vascular effects are endothelium-independent, as demonstrated by preserved vasodilation in patients with Gitelman syndrome (NCC deficiency).

The pharmacological distinction between true thiazides (benzothiadiazine derivatives, such as hydrochlorothiazide) and thiazide-like agents (phthalimidine derivative chlorthalidone and indoline derivative indapamide) is clinically significant. Chlorthalidone has a substantially longer half-life (40-60 hours vs 6-15 hours for hydrochlorothiazide) because of extensive partitioning into erythrocytes, which serve as a slow-release reservoir, providing more consistent 24-hour ambulatory blood pressure control, particularly during the vulnerable early-morning hours.[5] Indapamide possesses additional direct vasodilatory properties mediated through calcium channel antagonism and prostaglandin-mediated effects, potentially conferring cardiovascular benefit beyond diuresis alone.[45]

Calcium Channel Blockers

Calcium channel blockers exert their effects by inhibiting L-type (long-lasting) voltage-gated calcium channels (Cav1.2), encoded by CACNA1C, which mediate calcium influx during membrane depolarization. The L-type channel is a heteromeric complex comprising α₁C (pore-forming), α₂δ-, β-, and γ subunits. All calcium channel blockers bind to the α₁C  subunit but at distinct receptor sites, which accounts for their differing pharmacological profiles.[11]

Dihydropyridines (eg, amlodipine, nifedipine, felodipine, and lercanidipine) bind preferentially to the inactivated state of the L-type channel in vascular smooth muscle cells, exhibiting voltage-dependent blockade. Because vascular smooth muscle operates at more depolarized membrane potentials than cardiac myocytes, dihydropyridines achieve approximately 100-fold greater selectivity for vascular versus cardiac tissue.[46] The resultant arteriolar vasodilation reduces systemic vascular resistance without significant negative inotropic or chronotropic effects. Amlodipine uniquely possesses a charged, amphiphilic molecular structure that allows it to embed within the lipid bilayer of the cell membrane, creating a membrane depot effect that accounts for its exceptionally long half-life (35-50 hours) and a gradual onset of action, thereby minimizing reflex sympathetic activation.[46] 

Nondihydropyridines bind preferentially to the activated state of the L-type channel in cardiac tissue, producing frequency-dependent blockade. Verapamil (phenylalkylamine) binds to the channel's inner pore from the intracellular side, producing potent negative inotropic, chronotropic, and dromotropic effects. Diltiazem (benzothiazepine) binds to a distinct site that overlaps both the dihydropyridine and verapamil binding sites, resulting in intermediate cardiac effects. Both agents suppress sinoatrial node automaticity and slow atrioventricular conduction by reducing calcium-dependent phase 0 depolarization in nodal tissue.[11] The negative inotropic effect of nondihydropyridines on ventricular myocardium reduces myocardial oxygen consumption, making them useful in stable angina, but hazardous in systolic heart failure.

Angiotensin-Converting Enzyme Inhibitors

ACE inhibitors competitively block the zinc metallopeptidase ACE (also designated kininase II or CD143), which catalyzes 2 critical reactions: conversion of the decapeptide angiotensin I to the octapeptide angiotensin II and degradation of bradykinin into inactive metabolites.[47][48] By inhibiting angiotensin II production, ACE inhibitors reduce direct arteriolar and venous vasoconstriction, aldosterone secretion from the adrenal zona glomerulosa, sympathetic nervous system activation, vasopressin secretion, and cardiac and vascular smooth muscle hypertrophy and fibrosis mediated by angiotensin II stimulation of angiotensin II type 1 (AT1) receptor–linked growth factor signaling. 

Additionally, ACE inhibitors reduce constriction of the renal efferent arterioles, thereby lowering intraglomerular pressure and proteinuria.[47][48] Simultaneously, ACE inhibition potentiates bradykinin by preventing its degradation. Accumulated bradykinin stimulates β₂ receptors on vascular endothelium, triggering a signaling cascade through phospholipase A2 and phospholipase C that releases nitric oxide, prostacyclin via cyclooxygenase activation, and endothelium-derived hyperpolarizing factor. These mediators produce vasodilation, antiproliferative effects, and fibrinolytic activity.[47][48] 

Angiotensin II Receptor Blockers

ARBs selectively and competitively antagonize the AT1 receptor, a G-protein–coupled receptor that mediates vasoconstriction, aldosterone secretion, sympathetic facilitation, cellular proliferation, oxidative stress, and inflammation.[49] Unlike ACE inhibitors, ARBs do not inhibit kininase II and therefore do not increase bradykinin levels, explaining their lower rates of cough (1%-4% versus 5%-20%) and angioedema. However, this difference also means that ARBs lack bradykinin-mediated effects on endothelial function, fibrinolysis, and nitric oxide release.

Circulating angiotensin II levels increase during ARB therapy (due to loss of AT1-mediated negative feedback on renin release), which stimulates the unblocked angiotensin II type 2 (AT2) receptor. AT2 receptor activation produces vasodilation (via nitric oxide and cyclic guanosine monophosphate [GMP] pathways), antiproliferative effects, and natriuresis, potentially contributing to the therapeutic benefit of ARBs.[49]

Individual ARBs differ in their pharmacokinetic properties, which influence clinical selection. Telmisartan has the longest half-life (approximately 24 hours) and highest lipophilicity among agents in this class, providing consistent 24-hour blood pressure control and superior tissue penetration. Telmisartan also acts as a partial agonist of peroxisome proliferator–activated receptor γ, which confers insulin-sensitizing effects.[15] Losartan is distinguished by its uricosuric effect, which reduces serum uric acid by 15% to 30% by inhibiting the URAT1 urate transporter in the proximal tubule, which may be beneficial in patients with concomitant hyperuricemia or gout.[50]

β-Adrenergic Receptor Blockers

β-Blockers exert their antihypertensive effects by antagonizing the binding of catecholamines (epinephrine and norepinephrine) to β-adrenergic receptors. Three β-receptor subtypes are pharmacologically relevant: β₁ receptors (located predominantly in cardiac myocytes, the sinoatrial and atrioventricular nodes, and juxtaglomerular cells); β₂ receptors (found in bronchial and vascular smooth muscle, hepatocytes, and pancreatic β cells); and β₃ receptors (which are expressed in adipose tissue, myocardium, and vascular endothelium).[51] 

β-Blockers reduce blood pressure through multiple mechanisms: (i) decreased heart rate and myocardial contractility (negative chronotropy and inotropy via β₁ blockade), reducing cardiac output by 15% to 20%; (ii) suppression of renin release from juxtaglomerular cells (β₁-mediated), leading to decreased circulating angiotensin II and aldosterone; (iii) reduction of central sympathetic outflow from the vasomotor center, particularly lipophilic agents that cross the blood-brain barrier, such as propranolol, metoprolol, carvedilol; and (iv) presynaptic β₂ receptor blockade, reducing norepinephrine release from sympathetic nerve terminals.[51][52]

β-Blockers are classified by selectivity and ancillary properties. First-generation nonselective agents (eg, propranolol, nadolol, and timolol) block both β₁- and β₂ receptors equally. Second-generation cardioselective agents (eg, metoprolol, bisoprolol, atenolol, and betaxolol) preferentially block β₁ receptors at therapeutic doses, although selectivity is relative and dose-dependent. Third-generation vasodilating β-blockers provide additional blood pressure reduction through distinct vasodilatory mechanisms: carvedilol produces concurrent α₁ adrenergic receptor blockade and exhibits antioxidant properties through direct free-radical scavenging; nebivolol stimulates endothelial nitric oxide synthase via β₃ receptor agonism. Labetalol combines nonselective β-blockade with α₁ adrenergic blockade in an approximately β-to-α ratio of 3:1 intravenously and 7:1 orally.[52]

Loop Diuretics

Loop diuretics inhibit the sodium-potassium-2 chloride cotransporter (NKCC2), which is encoded by the SLC12A1 gene, on the luminal membrane of the thick ascending limb of the loop of Henle, which normally reabsorbs approximately 25% to 30% of filtered sodium. By blocking NKCC2, loop diuretics abolish the lumen-positive transepithelial voltage generated by potassium recycling, which drives paracellular reabsorption of calcium and magnesium. This mechanism accounts for the calciuric and magnesiuric effects of loop diuretics, in contrast to the hypocalciuric effect of thiazides.[21] Loop diuretics also reduce the medullary osmotic gradient by impairing countercurrent multiplication, thereby decreasing the ability to concentrate urine and free-water reabsorption.

Mineralocorticoid Receptor Antagonists

Steroidal mineralocorticoid receptor antagonists (eg, spironolactone and eplerenone) competitively bind the mineralocorticoid receptor in the principal cells of the cortical collecting duct. By blocking aldosterone binding, these agents inhibit the epithelial sodium channel and the sodium-potassium ATPase, thereby decreasing sodium reabsorption and reducing potassium and hydrogen ion excretion.[53] Beyond renal epithelial effects, mineralocorticoid receptor activation in the cardiovascular system drives cardiac fibrosis, vascular inflammation, endothelial dysfunction, and oxidative stress. Results from the Randomized Aldactone Evaluation Study (RALES) demonstrated that spironolactone reduced mortality by 30% in severe heart failure with reduced ejection fraction, and results from the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) demonstrated reduced mortality in post–myocardial infarction patients with left ventricular dysfunction, establishing mineralocorticoid receptor blockade as a therapeutic target beyond diuresis.[53]

Spironolactone is nonselective and binds progesterone and androgen receptors, which can cause gynecomastia, breast tenderness, menstrual irregularities, and sexual dysfunction. Eplerenone has greater receptor selectivity, which reduces these adverse effects but requires higher dosing. Finerenone, a nonsteroidal mineralocorticoid receptor antagonist, induces distinct receptor conformational changes that favor anti-inflammatory and antifibrotic gene expression and demonstrate a more balanced distribution across cardiac and renal tissues.[30]

Hydralazine

Hydralazine is a direct arteriolar vasodilator that reduces peripheral vascular resistance through multiple mechanisms, including inhibition of inositol trisphosphate–mediated calcium release, opening of potassium channels, interference with intracellular calcium mobilization, and possible stimulation of endothelial nitric oxide production. The selective arteriolar vasodilation reduces afterload without affecting preload, which triggers baroreceptor-mediated reflex tachycardia, sympathetic activation, and activation of the renin-angiotensin-aldosterone system, with secondary sodium and water retention.[54]

Central α₂ Agonists

Clonidine and guanfacine are imidazoline-derivative agonists that stimulate α₂ adrenergic receptors and imidazoline I1 receptors in the rostral ventrolateral medulla, the primary brainstem center responsible for controlling sympathetic outflow. Activation of these receptors reduces excitatory signaling to preganglionic sympathetic neurons, decreasing systemic norepinephrine release, heart rate, and peripheral vascular resistance. Clonidine also stimulates presynaptic α₂ autoreceptors on peripheral sympathetic nerve terminals, further reducing norepinephrine release.[55]

Minoxidil

Minoxidil is a prodrug that is sulfated in the liver by sulfotransferase enzyme SULT1A1 to its active metabolite—minoxidil sulfate. This metabolite activates ATP-sensitive potassium channels in vascular smooth muscle cells, thereby hyperpolarizing the membrane, closing voltage-dependent calcium channels, and causing profound arteriolar vasodilation. The resulting decrease in systemic vascular resistance triggers reflex sympathetic activation, activation of the renin-angiotensin-aldosterone system, and renal sodium retention, necessitating concurrent β-blocker and loop diuretic therapy.[55]

α₁ Adrenergic Receptor Blockers

α₁ Blockers (eg, doxazosin, prazosin, and terazosin) competitively antagonize postsynaptic α₁ adrenergic receptors (α_1A, α_1B, and α_1D subtypes) on vascular smooth muscle. Blockade causes arteriolar and venous dilation, reducing both afterload and preload.[24]

Emerging Agent Mechanisms

Aprocitentan: Aprocitentan is a dual endothelin receptor antagonist that blocks both ETA receptors, located on vascular smooth muscle and responsible for mediating vasoconstriction, cellular proliferation, and fibrosis, and ETB receptors, located on endothelial cells and involved in nitric oxide and prostacyclin release, as well as on vascular smooth muscle, where they contribute to vasoconstriction. Dual receptor blockade provides more complete suppression of endothelin-1 signaling than selective ETA antagonism, although ETB blockade may reduce endothelin clearance and impair nitric oxide–mediated vasodilation. The overall effect is potent vasodilation, reduced vascular remodeling, and decreased sodium reabsorption through inhibition of endothelin-1–mediated epithelial sodium channel activation in the collecting duct.[25]

Baxdrostat: Baxdrostat selectively inhibits aldosterone synthase (CYP11B2), a cytochrome P450 enzyme, which is responsible for catalyzing the final 3 steps of aldosterone biosynthesis in the adrenal zona glomerulosa: 11β-hydroxylation, 18-hydroxylation, and 18-oxidation of 11-deoxycorticosterone to aldosterone. Baxdrostat demonstrates greater than 100-fold selectivity for CYP11B2 over CYP11B1, thereby reducing aldosterone production without significantly affecting cortisol, corticosterone, or adrenal androgen synthesis. This selectivity has been supported by normal cosyntropin stimulation test results observed in clinical trials.[26]

Zilebesiran: Zilebesiran uses N-acetylgalactosamine–conjugated small interfering RNA technology to enable hepatocyte-specific uptake through the asialoglycoprotein receptor. Following internalization, the small interfering RNA guide strand is incorporated into the RNA-induced silencing complex, where it directs cleavage of angiotensinogen messenger RNA. This process depletes hepatic angiotensinogen stores and suppresses activation of the renin-angiotensin-aldosterone system cascade.[37]

Administration

Thiazide and Thiazide-Like Diuretics

All thiazide-type diuretics are administered orally once daily, preferably in the morning to minimize nocturia, although the MAPEC and HYGIA trials suggested potential benefit of nighttime dosing for nondipping patterns. Findings from the Treatment in Morning Versus Evening (TIME) trial subsequently questioned this benefit, showing no significant difference in outcomes between morning and evening dosing.[56] 

Hydrochlorothiazide: Hydrochlorothiazide is typically initiated at 12.5 mg daily and may be titrated to 25 to 50 mg daily. The drug has a bioavailability of 65% to 75%, a half-life of 6 to 15 hours, an onset of action of approximately 2 hours, a peak effect within 4 to 6 hours, and a duration of action of 6 to 12 hours.

Chlorthalidone: Chlorthalidone is typically initiated at 12.5 mg daily and may be titrated to 25 to 50 mg daily, although doses up to 100 mg are rarely used. The drug has a bioavailability of 64% and a prolonged half-life of 40 to 60 hours due to extensive erythrocyte partitioning and binding to carbonic anhydrase, which creates a slow-release reservoir. The onset of action occurs within 2 to 3 hours, the peak effect is attained within 2 to 6 hours, and the duration of action ranges from 48 to 72 hours.

Indapamide: Indapamide is typically administered at a dosage of 1.25 to 2.5 mg daily. The drug has a bioavailability of 93%, a half-life of 14 to 18 hours, and undergoes extensive hepatic metabolism primarily through CYP3A4.[45]

Chlorthalidone and hydrochlorothiazide are not equipotent at equivalent milligram doses. Pharmacokinetic modeling suggests that chlorthalidone 12.5 mg provides approximately equivalent 24-hour natriuresis to hydrochlorothiazide 25 mg.

Calcium Channel Blockers

Amlodipine: Amlodipine is administered at a dosage of 2.5 to 10 mg once daily. The drug has a bioavailability of 64% to 90% and a prolonged half-life of 35 to 50 hours, allowing true once-daily dosing with minimal peak-to-trough variation. Amlodipine undergoes extensive hepatic metabolism via CYP3A4 to inactive metabolites and does not produce clinically significant active metabolites. The medication may be taken without regard to food. Therapy is typically initiated at 5 mg daily (or at 2.5 mg daily in older adults or patients with hepatic impairment). Steady-state concentrations are generally achieved within 7 to 8 days.

Nifedipine extended-release: Nifedipine extended-release is administered at a dosage of 30 to 120 mg once daily and uses a gastrointestinal therapeutic system osmotic push-pull delivery mechanism. The drug has a bioavailability of 84% to 89% and a half-life of approximately 7 hours, which is extended to 12 to 24 hours with the extended-release formulation. Nifedipine is metabolized primarily through CYP3A4 and is a substrate of this enzyme system.

Felodipine extended-release: Felodipine extended-release is administered at a dosage of 2.5 to 10 mg once daily and demonstrates a high vascular selectivity ratio (100:1 vascular-to-cardiac selectivity ratio).[46]

Diltiazem extended-release: Diltiazem extended-release is administered at a dosage of 120 to 480 mg once daily, although dosing frequency may vary depending on the formulation. The drug has a bioavailability of 40% to 67% due to extensive first-pass hepatic metabolism and a parent-compound half-life of 3 to 8 hours, which is prolonged with extended-release formulations. Intravenous diltiazem may be administered as a 0.25 mg/kg bolus over 2 minutes for acute ventricular rate control in patients with atrial fibrillation.

Verapamil extended-release: Verapamil extended-release is administered at a dosage of 120 to 480 mg once daily. The drug has a bioavailability of 20% to 35% due to an extensive first-pass effect and a half-life of 6 to 8 hours. Intravenous verapamil may be administered as a 2.5 to 5 mg bolus for the acute management of supraventricular tachycardia.[46]

Angiotensin-Converting Enzyme Inhibitors

Most ACE inhibitors are administered as prodrugs (except captopril and lisinopril) and require hepatic esterase–mediated hydrolysis to their active diacid forms. This requirement has implications in hepatic impairment, where activation may be delayed.

Lisinopril: Lisinopril is administered at a dosage of 10 to 40 mg once daily. This is unique among ACE inhibitors because it is hydrophilic, does not undergo hepatic metabolism, and is excreted entirely by the kidneys. Lisinopril has a bioavailability of approximately 25% and a half-life of about 12 hours.

Ramipril: Ramipril is administered at a dosage of 2.5 to 20 mg daily, given once or twice daily. This is a prodrug that is converted to the active metabolite ramiprilat and demonstrates high affinity for tissue ACE. Ramiprilat has a half-life of 13 to 17 hours. Clinical benefit has been supported by the outcomes of the HOPE trial.[12] 

Enalapril: Enalapril is administered at a dosage of 5 to 40 mg daily, given once or twice daily. This is a prodrug that is converted to the active metabolite enalaprilat. Enalaprilat is the only ACE inhibitor available for parenteral administration and may be administered intravenously at a dosage of 1.25 mg every 6 hours for hypertensive emergencies.

Perindopril: Perindopril is administered at a dosage of 4 to 16 mg once daily. This is a prodrug that is converted to perindoprilat and demonstrates high affinity for tissue ACE. Cardiovascular benefit has been supported by findings from the EUROPA trial. Most ACE inhibitors require dose reduction in patients with renal impairment (except fosinopril, which undergoes dual hepatic and renal elimination).[48]

Angiotensin II Receptor Blockers

All ARBs are administered orally.

Losartan: Losartan is administered at a dosage of 50 to 100 mg once daily. The drug is metabolized to the active metabolite EXP-3174, which is 10 to 40 times more potent at the AT1 receptor and has a half-life of 6 to 9 hours. Losartan is unique among ARBs in possessing a clinically significant uricosuric effect.

Valsartan: Valsartan is administered at a dosage of 80 to 320 mg once daily. The drug does not produce active metabolites, has a bioavailability of approximately 23%, and a half-life of about 6 hours. Valsartan is available in single-pill combinations with hydrochlorothiazide or amlodipine at doses of 160 and 320 mg, and is also available in combination with sacubitril as Sacubitril/valsartan (Entresto).

Telmisartan: Telmisartan is administered at a dosage of 20 to 80 mg once daily. The drug has the longest half-life among ARBs (24 hours) and demonstrates the greatest lipophilicity and volume of distribution within the class. Telmisartan also exhibits partial agonist activity at peroxisome proliferator–activated receptor γ. The drug is eliminated primarily through hepatic pathways and does not require dose adjustment in renal impairment. Among ARBs, telmisartan provides one of the most consistent trough-to-peak blood pressure control ratios.

Olmesartan: Olmesartan is administered at a dosage of 20 to 40 mg once daily and has been associated with rare cases of sprue-like enteropathy, which is characterized by severe, chronic diarrhea and villous atrophy.

Azilsartan medoxomil: Azilsartan medoxomil is administered at a dosage of 40 to 80 mg once daily and has the highest binding affinity for the AT1 receptor among ARBs. Results from head-to-head clinical trials have shown greater reductions in blood pressure with azilsartan medoxomil than with olmesartan and valsartan.[49]

β-Blockers

β-Blockers exhibit considerable variability in pharmacokinetic properties across individual agents within the class.

Metoprolol tartrate: Metoprolol tartrate is administered at a dosage of 50 to 200 mg twice daily (immediate-release formulation). Individuals who are poor CYP2D6 metabolizers, estimated to comprise approximately 7% to 10% of White populations, may experience exaggerated effects. Metoprolol succinate extended-release is administered at a dosage of 25 to 200 mg once daily and utilizes zero-order release kinetics.

Bisoprolol: Bisoprolol is administered at a dosage of 2.5 to 10 mg once daily and demonstrates high β1 selectivity among β-blockers. The drug undergoes approximately 50% hepatic and 50% renal elimination, with a half-life of 10 to 12 hours.

Atenolol: Atenolol is administered at a dosage of 25 to 100 mg once daily. The drug is hydrophilic, undergoes renal excretion, and has a half-life of 6 to 7 hours, which may result in less consistent 24-hour blood pressure control. Atenolol is no longer recommended by most current guidelines.

Carvedilol: Carvedilol is administered at a dosage of 6.25 to 25 mg twice daily in the immediate-release formulation or 10 to 80 mg once daily in the controlled-release formulation. In addition to nonselective β-blockade, carvedilol also exerts α1-adrenergic receptor blockade.

Nebivolol: Nebivolol is administered at a dosage of 5 to 40 mg once daily. The drug demonstrates high β1 selectivity at lower doses and promotes vasodilation through stimulation of endothelial nitric oxide synthase mediated by β₃ receptor agonism.

Labetalol: Labetalol is administered orally at a dosage of 200 to 1200 mg twice daily. For hypertensive emergencies, it may be administered intravenously as a 20 mg bolus, which may be repeated or followed by a continuous infusion at 0.5 to 2 mg/min. Labetalol is a preferred agent for the management of hypertension during pregnancy.[51][52]

Loop Diuretics

Furosemide: Furosemide is administered at a dosage of 20 to 80 mg once or twice daily, with doses up to 600 mg/d used in advanced CKD or heart failure. The drug demonstrates highly variable oral bioavailability, ranging from 10% to 100% (average approximately 50%), and has a half-life of 1 to 2 hours. Oral absorption may be erratic and is often further impaired by gut edema in patients with decompensated heart failure. The approximate intravenous-to-oral dose conversion ratio is 1:2.

Bumetanide: Bumetanide is administered at a dosage of 0.5 to 2 mg once or twice daily and demonstrates more predictable oral bioavailability of approximately 80% to 100%. The equipotent dose ratio of the drug relative to furosemide is approximately 1:40.

Torsemide: Torsemide is administered at a dosage of 5 to 20 mg once daily for hypertension, with doses up to 200 mg used in patients with heart failure or CKD. The drug has an oral bioavailability of 80% to 100% and a half-life of 3 to 4 hours. In addition to loop diuretic activity, torsemide inhibits aldosterone receptor binding and is associated with less potassium wasting than furosemide. A dose of 20 mg torsemide is approximately equivalent to 40 to 80 mg furosemide.[21]

Mineralocorticoid Receptor Antagonists

Spironolactone: Spironolactone is administered at a dosage of 25 to 50 mg once daily for hypertension, with doses up to 100 mg used in selected patients. The drug has a bioavailability greater than 90%, which is enhanced when taken with food, and undergoes extensive hepatic metabolism to multiple active metabolites, primarily canrenone, which has a half-life of 16 to 22 hours. The antihypertensive effect develops gradually over 2 to 4 weeks. The incidence of gynecomastia increases with higher doses and longer duration of therapy.

Eplerenone: Eplerenone is administered at a dosage of 50 mg once or twice daily. The drug has a bioavailability of approximately 69%, is metabolized via the CYP3A4 substrate, and should not be coadministered with strong CYP3A4 inhibitors. Eplerenone has a half-life of 4 to 6 hours, demonstrates approximately 500-fold greater selectivity for the mineralocorticoid receptor than spironolactone, and does not produce active metabolites.

Finerenone: Finerenone is administered at a dosage of 10 to 20 mg once daily. The drug is a CYP3A4 substrate, has a half-life of 2 to 3 hours, and demonstrates a rapid onset of action. Unlike spironolactone, which preferentially concentrates in renal tissue, finerenone demonstrates a more balanced distribution between cardiac and renal tissues.[30][31]

Hydralazine

Hydralazine can be administered orally or parenterally.

Oral dosing: Oral therapy is typically initiated at 10 mg 4 times daily for the first 2 to 4 days, followed by 25 mg 4 times daily during the first week, and then increased to 50 mg 4 times daily thereafter. The maximum recommended dosage is 300 mg/d; however, doses greater than 200 mg/d are associated with a substantially increased risk of drug-induced lupus erythematosus.[54]

The frequent dosing requirement (3-4 times daily) because of its short half-life (2-4 hours for the parent compound and 7-16 hours for active hydrazine metabolites) limits adherence. Oral bioavailability is highly variable (10% to 26% in fast acetylators and 40% to 55% in slow acetylators) owing to extensive first-pass hepatic metabolism via N-acetyltransferase-2 polymorphism. Slow acetylators achieve higher plasma concentrations and face a significantly greater risk of drug-induced lupus erythematosus; acetylator phenotype should be considered when escalating to doses above 200 mg/d.[54]

Parenteral administration: Parenteral hydralazine may be administered intravenously or intramuscularly at a dosage of 5 to 10 mg every 20 to 30 minutes, with a maximum of 20 mg intravenously or 40 mg intramuscularly per treatment episode. This drug is commonly used for hypertensive emergencies, particularly in patients with eclampsia or preeclampsia, in whom it remains a first-line agent. The onset of action occurs within 5 to 20 minutes after intravenous administration and within 10 to 30 minutes after intramuscular administration. Food increases the oral bioavailability of hydralazine. Hydralazine is typically administered in combination with a β-blocker and a diuretic to counteract reflex tachycardia and fluid retention.[54]

Central α₂ Agonists

Clonidine is available in oral (immediate-release tablets), transdermal patch, and injectable formulations.

Oral clonidine: Oral clonidine is typically initiated at 0.1 mg twice daily and may be titrated in increments of 0.1 mg/d at weekly intervals. The usual maintenance dosage ranges from 0.2 to 0.6 mg/d in divided doses administered twice to 3 times daily, with a maximum dosage of 2.4 mg/d. Clonidine has a bioavailability of 75% to 100% and a half-life of 6 to 20 hours (mean approximately 12 hours), which is prolonged in patients with renal impairment. Approximately 50% of the drug is excreted unchanged in the urine; therefore, dose adjustment is required in severe Chronic Kidney Disease with an eGFR less than 30 mL/min/1.73 m².[55]

Transdermal clonidine (Catapres-TTS): Transdermal clonidine (Catapres-TTS) is available as patches that deliver 0.1, 0.2, or 0.3 mg/d over 7 days. The patch is applied to a hairless area of the upper outer arm or anterior chest, with weekly rotation of application sites. Therapeutic plasma concentrations are typically achieved within 2 to 3 days after initial application. Compared with oral formulations, transdermal clonidine provides more stable plasma concentrations, avoids first-pass metabolism, improves adherence through once-weekly administration, and substantially reduces the incidence of dry mouth and sedation. When central α2 agonist therapy is indicated, the transdermal formulation is generally preferred.[55]

Minoxidil

Minoxidil is administered orally.

Initial dose: Minoxidil is typically initiated at 5 mg once daily, although a lower starting dose of 2.5 mg once daily may be used in older adults or in patients receiving concurrent diuretic therapy. Dosage may be titrated in increments of 5 to 10 mg at intervals of at least 3 days.

Usual maintenance: The usual maintenance dosage of minoxidil is 10 to 40 mg/d administered in 1 or 2 divided doses, with a maximum dosage of 100 mg/d. Minoxidil has a bioavailability of approximately 90%. Although the parent compound has a half-life of 3 to 4 hours, the active metabolite, minoxidil sulfate, which is produced through hepatic sulfation by SULT1A1, has a duration of action of approximately 24 hours, allowing once- or twice-daily dosing. Peak antihypertensive effect generally occurs 2 to 3 hours after oral administration.[23]

α₁ Adrenergic Receptor Blockers

Doxazosin: Doxazosin is typically initiated at 1 mg once daily at bedtime to minimize the risk of first-dose syncope. The dosage may be titrated gradually at 1- to 2-week intervals to 2 to 8 mg daily, with a maximum dosage of 16 mg/d. Doxazosin has a bioavailability of approximately 65% and a half-life of 15 to 22 hours, allowing once-daily administration. Extended-release doxazosin (Cardura XL) administered at 4 to 8 mg daily provides more stable plasma concentrations.

Prazosin: Prazosin is typically initiated at 0.5 mg administered twice or 3 times daily, as the risk of the first-dose phenomenon is greatest with this agent. The usual maintenance dosage ranges from 2 to 20 mg/d in 2 to 3 divided doses, with a maximum dosage of 40 mg/d. Prazosin has a half-life of 2 to 3 hours, necessitating multiple daily doses.

Terazosin: Terazosin is typically initiated at 1 mg at bedtime and may be titrated to 1 to 20 mg/d administered in 1 or 2 divided doses. The drug has a half-life of 8 to 13 hours.[24]

Newer Agents

Aprocitentan: Aprocitentan is administered orally at a dosage of 12.5 mg once daily and is available exclusively through the Tryvio Risk Evaluation and Mitigation Strategy (REMS) program. The drug has a half-life of approximately 44 hours, undergoes hepatic metabolism, and does not require dose adjustment in patients with renal impairment. Pregnancy testing is required before treatment initiation and monthly during therapy, and reliable contraception is mandatory during treatment.[25]

Zilebesiran: Zilebesiran is administered as a subcutaneous injection at doses of 300 to 600 mg every 3 or 6 months. Blood pressure reduction typically begins within 2 to 4 weeks, with maximal effect observed at 8 weeks. The duration of effect is approximately 24 weeks with the 300 mg dose and greater than 24 weeks with the 600 mg dose. Its antihypertensive effect is not rapidly reversible because the recovery of angiotensinogen levels depends on new hepatic protein synthesis over a period of weeks to months. Zilebesiran is administered in healthcare settings and requires cold-chain storage.[38]

Adverse Effects

Thiazide and Thiazide-Like Diuretics

Metabolic effects are dose-related and represent the primary limitation of thiazide therapy. Hypokalemia (most common, occurring in 10% to 40% at higher doses) results from increased sodium delivery to the collecting duct, stimulating epithelial sodium channel–mediated sodium reabsorption coupled with potassium secretion via renal outer medullary potassium channels, and is compounded by secondary hyperaldosteronism due to volume depletion. Hypokalemia increases the risk of ventricular arrhythmias, particularly in patients receiving digoxin or with prolonged QTc intervals. Chlorthalidone produces more hypokalemia than hydrochlorothiazide at equipotent doses (6.0% vs 4.4% in the Diuretic Comparison Project).[6] Hyponatremia, which occurs more commonly in older women and individuals with low body mass, can be severe and life-threatening and results from impaired free-water excretion in the diluting segment of the nephron. Hyperuricemia, caused by competition for the organic anion transporters OAT1 and OAT3 in the proximal tubule, may precipitate gout. Hypercalcemia is typically mild and occurs through enhanced proximal reabsorption secondary to volume depletion. Impaired glucose tolerance results from hypokalemia-induced impairment of pancreatic β-cell insulin secretion and decreased peripheral insulin sensitivity. Dyslipidemia, characterized by a transient increase in low-density lipoprotein cholesterol and triglycerides, usually resolves within 1 year. Photosensitivity dermatitis occurs rarely.[42]

Calcium Channel Blockers

Dihydropyridine-specific effects include peripheral edema in 5% to 30% of patients (dose-dependent), caused by preferential dilation of arterioles in the precapillary bed, which increases intracapillary hydrostatic pressure and transcapillary fluid filtration (Starling forces). This effect does not represent fluid retention and does not respond to diuretics. Coadministration of renin-angiotensin-aldosterone system inhibitors attenuates edema by inducing postcapillary venodilation and restoring the balance of capillary hydrostatic forces. Headache, flushing, and dizziness result from vasodilation.

Gingival hyperplasia occurs in 3% to 10% of patients (more common with nifedipine) and is caused by impaired collagen degradation by fibroblasts in the gingival tissue. Reflex tachycardia is more common with short-acting formulations. Calcium channel blockers inhibit platelet aggregation by suppressing calcium-dependent thromboxane A2 synthesis and glycoprotein IIb/IIIa activation, thereby increasing the risk of gastrointestinal tract bleeding, particularly in older adults and those receiving concurrent anticoagulation or antiplatelet therapy.[46]

Nondihydropyridine–specific effects include bradycardia and atrioventricular conduction delay, particularly hazardous when combined with β-blockers or digoxin. Constipation occurs in up to 25% of patients receiving verapamil because of calcium channel blockade in gastrointestinal smooth muscle, which requires proactive treatment. Negative inotropy can precipitate or worsen heart failure in patients with reduced systolic function. Both subclasses inhibit CYP3A4 and P-glycoprotein, causing clinically significant drug interactions with statins (including an increased risk of rhabdomyolysis with simvastatin doses >20 mg), calcineurin inhibitors (eg, cyclosporine and tacrolimus), and digoxin (verapamil increases digoxin levels by approximately 60% to 80%).[11][46]

Angiotensin-Converting Enzyme Inhibitors

Cough occurs in 5% to 20% of patients (higher in women, Asian patients, and nonsmokers) and is caused by the accumulation of bradykinin, substance P, and prostaglandins in the bronchial epithelium, which sensitizes the cough reflex via C-fiber stimulation. Onset is typically 1 to 6 months after initiation, and resolution requires 1 to 4 weeks after discontinuation. Substitution with an ARB is appropriate because cross-reactivity is rare (<3%).[47]

Angioedema occurs in 0.1% to 0.7% of patients (with a 4-fold higher risk in Black patients) due to bradykinin-mediated increases in vascular permeability in the submucosa. This condition typically involves the face, lips, tongue, and larynx, with potential airway compromise that may require emergent intervention, including epinephrine, airway management, and consideration of icatibant or a C1-esterase inhibitor concentrate in severe cases. Risk persists throughout therapy (median onset 1-2 years). ACE inhibitor–related angioedema is an absolute contraindication to rechallenge and a strong relative contraindication to ARB use, although cross-reactivity is less than 2%.[47][48]

Hyperkalemia occurs particularly when combined with potassium-sparing diuretics, nonsteroidal anti-inflammatory drugs, potassium supplements, trimethoprim, or heparin, and in patients with CKD (eGFR <30 mL/min/1.73 m²), diabetes mellitus, or heart failure. Acute kidney injury occurs through reduction of efferent arteriolar tone, which decreases intraglomerular pressure; a rise in serum creatinine of up to 30% is expected, but a rise greater than 30% should prompt evaluation for bilateral renal artery stenosis or volume depletion. First-dose hypotension is more common in patients who are volume-depleted or receiving high-dose diuretics. ACE inhibitors are teratogenic and can cause fetal renal tubular dysplasia, oligohydramnios, pulmonary hypoplasia, and skeletal malformations. Consequently, these agents are contraindicated in all trimesters throughout pregnancy.[47][48]

Angiotensin II Receptor Blockers

ARBs share the class effects of hyperkalemia, hypotension, and renal impairment with ACE inhibitors but have substantially lower rates of cough (1% to 4%, comparable to placebo) and angioedema (<0.1%). The teratogenicity risk is identical to that of ACE inhibitors. Dizziness and fatigue are the most commonly reported adverse effects. Rare hepatotoxicity has been reported, predominantly with losartan and irbesartan. Olmesartan has been uniquely associated with a sprue-like enteropathy characterized by severe chronic diarrhea, weight loss, and villous atrophy on duodenal biopsy, which resolves upon drug discontinuation. The mechanism is believed to involve cell-mediated immune injury to the intestinal mucosa.[49]

β-Blockers

Cardiovascular: Bradycardia, atrioventricular conduction delay, hypotension, and the precipitation of acute decompensated heart failure when initiated at high doses in patients with reduced systolic function, necessitating low-dose initiation and gradual titration. Cold extremities and worsening of Raynaud phenomenon occur because of unopposed alpha-mediated vasoconstriction.

Metabolic: Weight gain (average 1.2 kg), impaired glucose tolerance, and unfavorable lipid effects, including increased triglycerides and decreased high-density lipoprotein cholesterol. Carvedilol and nebivolol demonstrate more favorable metabolic profiles due to their vasodilatory properties and enhanced insulin sensitivity.[51][52]

Central nervous system: Fatigue, exercise intolerance, depression, vivid dreams, and sleep disturbances, which are more common with lipophilic agents that cross the blood-brain barrier. Respiratory adverse effects include bronchospasm, particularly with nonselective agents, which may unmask or worsen asthma; however, cardioselective agents can be used cautiously in chronic obstructive pulmonary disease. Sexual dysfunction occurs in approximately 5% to 15% of patients. Abrupt discontinuation can precipitate rebound hypertension, tachycardia, angina exacerbation, and rarely myocardial infarction because of upregulated β-receptor density and catecholamine supersensitivity. Gradual dose tapering over 1 to 2 weeks is therefore recommended.[51]

Mineralocorticoid Receptor Antagonists

Hyperkalemia is the most clinically significant class-wide adverse effect, resulting from blockade of aldosterone-mediated potassium secretion in principal cells of the cortical collecting duct. Risk factors include concurrent blockade of the renin-angiotensin-aldosterone system, CKD (eGFR <45 mL/min/1.73 m²), diabetes mellitus, potassium supplements, nonsteroidal anti-inflammatory drugs, and trimethoprim. Spironolactone-specific adverse effects reflect its nonselectivity for the mineralocorticoid receptor, including gynecomastia, breast tenderness, erectile dysfunction, decreased libido in men, and menstrual irregularities in premenopausal women. These effects are dose- and duration-dependent and often prompt discontinuation or switching to eplerenone or finerenone.[20][30][53]

Eplerenone is highly selective for the mineralocorticoid receptor and largely avoids antiandrogenic and progestational adverse effects. Gynecomastia rates with eplerenone are comparable to placebo. However, hyperkalemia remains the principal risk. Findings from the Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS) demonstrated that serious hyperkalemia (potassium ≥6.0 mEq/L) occurred in 5.5% of eplerenone-treated patients versus 3.9% of patients receiving placebo. Risk is amplified by concurrent use of an ACE inhibitor or ARB and CKD. Eplerenone can also cause dizziness, diarrhea, and, rarely, elevated hepatic transaminases. Drug interactions via CYP3A4 inhibition are clinically important because strong inhibitors are contraindicated and moderate inhibitors require dose adjustment.[53]

Finerenone demonstrates an improved adverse effect profile compared with steroidal mineralocorticoid receptor antagonists. Results from the Finerenone in Reducing Kidney Failure and Disease Progression in Diabetic Kidney Disease (FIDELIO-DKD) and Finerenone in Reducing Cardiovascular Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trials demonstrated that hyperkalemia leading to discontinuation occurred in 2.3% of finerenone-treated patients versus 0.9% of patients receiving placebo. Finerenone did not cause gynecomastia, breast pain, or antiandrogenic effects. The most common adverse event was hyperkalemia, which was generally manageable with dose adjustment and rarely required hospitalization. No cases of acute renal failure attributable to finerenone were reported. Results from the Finerenone Trial to Investigate Efficacy and Safety Superior to Placebo in Patients With Heart Failure (FINEARTS-HF) demonstrated similar safety findings, with modest rates of hyperkalemia and no excess renal adverse events.[32][33]

Hydralazine

The most clinically significant adverse effect is drug-induced lupus erythematosus, occurring in 5% to 10% of patients receiving doses greater than 200 mg/d and up to 20% at higher doses, predominantly in slow acetylators. Drug-induced lupus erythematosus presents with arthralgias, myalgias, fever, pleuritis, pericarditis, and positive antihistone antibodies. Symptoms usually resolve within weeks of drug discontinuation, though serological abnormalities may persist for months. Renal and central nervous system involvement are rare compared with idiopathic systemic lupus erythematosus.[54]

Reflex sympathetic activation causes tachycardia, palpitations, and increased cardiac output, which can provoke angina or myocardial ischemia in patients with underlying coronary artery disease. This effect necessitates concurrent β-blocker therapy. Fluid retention and edema from renin-angiotensin-aldosterone system activation and direct renal sodium retention necessitate concurrent diuretic use. Other adverse effects include headache, flushing, nasal congestion, nausea, diarrhea, and peripheral neuropathy.[54]

Central α₂ Agonists

Central nervous system depression is the predominant adverse effect. Sedation and drowsiness occur in 35% to 50% of patients (often decreases with continued use), dry mouth in 25% to 40% (reduced salivary gland secretion via α₂ stimulation), and dizziness in 15% to 20%. Other central nervous system effects include depression, vivid dreams or nightmares, cognitive impairment (particularly in older adults), and sexual dysfunction (erectile dysfunction in 10% to 20% of men, decreased libido).[55] Rebound hypertensive crisis is the most dangerous adverse effect and occurs with abrupt discontinuation, particularly with oral clonidine at doses greater than 0.6 mg/d or after more than 1 month of therapy. The mechanism involves upregulation of peripheral α-adrenergic receptors during chronic therapy; sudden withdrawal results in catecholamine excess, producing severe hypertension (systolic blood pressure greater than 200 mm Hg), tachycardia, tremor, diaphoresis, and headache that can mimic pheochromocytoma crisis.

Management requires reinstitution of clonidine or treatment with intravenous phentolamine. β-Blockers alone are contraindicated in rebound hypertension because unopposed α-adrenergic vasoconstriction can worsen the crisis. Transdermal clonidine carries a lower risk of rebound because of its gradual offset.[55] Other adverse effects include contact dermatitis with transdermal patches (15% to 20%), bradycardia and atrioventricular conduction delay, constipation, and rare hepatotoxicity with methyldopa. Clonidine should be used cautiously in patients with sinus node dysfunction, depression, or peripheral vascular disease.[55]

Minoxidil

Sodium and water retention are nearly universal (>80% of patients) in the absence of concurrent loop diuretic therapy, resulting from activation of the renin-angiotensin-aldosterone system and direct renal tubular sodium reabsorption. This can progress to peripheral edema, pulmonary edema, and pericardial effusion. Pericardial effusion occurs in approximately 3% of patients and can rarely progress to cardiac tamponade, which is life-threatening. Routine echocardiographic monitoring is recommended in the first months of therapy.[23]

Reflex tachycardia is pronounced due to potent arteriolar vasodilation, necessitating concurrent β-blocker therapy to prevent myocardial ischemia and increased myocardial oxygen demand. Hypertrichosis occurs in approximately 80% of patients after 3 to 6 weeks of oral therapy and affects the face, arms, back, and legs. This effect is cosmetically distressing, particularly in women, and reverses within 1 to 6 months after drug discontinuation.[23] Furthermore, electrocardiographic changes, including T-wave flattening or inversion and ST-segment changes, occur in up to 60% of patients without evidence of myocardial ischemia and likely reflect altered ventricular repolarization. Other adverse effects include headache, nausea, and rare Stevens-Johnson syndrome.[23]

α₁ Adrenergic Receptor Blockers

First-dose syncope and orthostatic hypotension are hallmark adverse effects, resulting from an abrupt reduction in peripheral vascular resistance without adequate compensatory reflex tachycardia. Risk is greatest with prazosin, in volume-depleted patients, and when initiated at higher doses or during the daytime. Initiation at bedtime with the lowest available dose minimizes this risk.[55]

Heart failure: The ALLHAT trial demonstrated a 25% increase in combined cardiovascular events and a 2-fold increase in heart failure incidence with doxazosin compared with chlorthalidone, leading to early termination of the doxazosin arm and removing α₁ blockers from consideration as first-line antihypertensive monotherapy.[55] The mechanism likely involves chronic neurohormonal activation (increased plasma norepinephrine and renin-aldosterone-angiotensin activation) and fluid retention.

Other adverse effects include dizziness (10% to 20%), headache (5% to 15%), fatigue, nasal congestion (α₁-mediated vasodilation of the nasal mucosa), retrograde ejaculation (particularly relevant in younger men), and intraoperative floppy iris syndrome during cataract surgery. This syndrome occurs because α_1A receptors mediate contraction of the iris dilator muscle; blockade results in poor pupillary dilation, iris billowing, and progressive intraoperative miosis. Ophthalmologists must be informed of any current or prior use of α₁ blockers before cataract surgery. Tamsulosin carries the highest risk, but all α₁ blockers have been implicated.[55]

Newer Agents

Aprocitentan: Aprocitentan is associated with peripheral edema and fluid retention, occurring in approximately 9% of patients receiving 12.5 mg and 18% of those receiving 25 mg, compared with 2% in placebo-treated patients. These effects are thought to result from combined vasodilation and renal sodium retention. Other adverse effects include anemia, which may be dilutional and may also involve suppression of erythropoietin production, headache, and nasal congestion. Potential hepatotoxicity has been reported, and periodic liver function monitoring is recommended. Aprocitentan is teratogenic (Category X equivalent, Risk Evaluation and Mitigation Strategy required). Unlike bosentan (a first-generation endothelin receptor antagonist), aprocitentan has not demonstrated a significant hepatotoxicity signal in clinical studies; however, long-term safety surveillance remains ongoing.[25]

Baxdrostat: Baxdrostat has demonstrated a favorable safety profile in clinical trials. No evidence of adrenocortical insufficiency has been observed at doses up to 2 mg, with cortisol concentrations remaining within the reference range and showing appropriate responses to cosyntropin stimulation. Mild elevations in serum potassium may occur. Although clinically significant adrenal insufficiency has not been observed, a theoretical risk exists during physiologic stress states, such as acute illness or surgery, warranting ongoing monitoring.[28]

Zilebesiran: Zilebesiran is associated with injection-site reactions, reported in approximately 16.9% of treated patients, and mild hyperkalemia. The prolonged duration and limited reversibility of angiotensinogen suppression raise theoretical concerns regarding the inability to rapidly reverse hypotension during intercurrent illness, surgery, or dehydration. Currently, no specific antidote is available.[38]

Contraindications

Thiazide and Thiazide-Like Diuretics

Absolute contraindications: Anuria, in which no diuretic effect can be achieved, and hypersensitivity to the specific agent. Historical concerns regarding cross-reactivity with sulfonamide antibiotics have been largely debunked. The allergenic sulfonamide moiety in antibiotics (N1-substituted sulfonamide) differs structurally from the nonantibiotic sulfonamide in thiazides, and large observational studies have not confirmed clinically significant cross-reactivity.

Relative contraindications: Symptomatic hyponatremia, severe hypokalemia, refractory gout, pregnancy (because of the risk of neonatal thrombocytopenia and hyponatremia), and an eGFR less than 30 mL/min/1.73 m² (where antihypertensive efficacy may be reduced, although indapamide may retain some effect).[42]

Calcium Channel Blockers

Absolute contraindications for all calcium channel blockers: Hypersensitivity to the drug.

Dihydropyridines: Cardiogenic shock, severe aortic stenosis (risk of syncope from afterload reduction without ability to augment cardiac output), and acute coronary syndrome (short-acting formulations only, due to reflex sympathetic activation).

Nondihydropyridines: Heart failure with reduced ejection fraction (left ventricular ejection fraction <40%), second- or third-degree atrioventricular block (without pacemaker), sick sinus syndrome (without pacemaker), and concurrent intravenous β-blocker administration because of the risk of severe bradycardia and asystole.

Relative contraindications: Hepatic impairment, in which extensive first-pass metabolism may increase drug exposure; concomitant use of CYP3A4 inhibitors with verapamil or diltiazem, due to the risk of toxic accumulation; and concurrent digoxin use with verapamil, which may require a 50% reduction in the digoxin dose.[11]

Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers

Absolute contraindications (both classes): Pregnancy (all trimesters) because of teratogenic effects, including fetal renal tubular dysgenesis, oligohydramnios, and skeletal malformations; bilateral renal artery stenosis or renal artery stenosis in a solitary functioning kidney because of the risk of acute renal failure resulting from loss of efferent arteriolar tone required to maintain GFR); and concurrent aliskiren use in patients with diabetes mellitus or an eGFR less than 60 mL/min.

Angiotensin-converting enzyme inhibitor-specific contraindications: Prior ACE inhibitor–related angioedema (absolute contraindication) and history of hereditary or idiopathic angioedema (absolute contraindication).

Relative contraindications: Hyperkalemia greater than 5.5 mEq/L, severe volume depletion (which should be corrected before initiating therapy), severe aortic stenosis (because of the risk of hypotension), advanced CKD with an eGFR less than 20 mL/min (requiring careful monitoring with expectation of modest increase in serum creatinine), and women of childbearing potential without reliable contraception.[47][48][49]

β-Blockers

Absolute contraindications: Severe sinus bradycardia (<50 beats/min), second- or third-degree atrioventricular block (without a pacemaker), decompensated heart failure (acute initiation; may be carefully introduced once stabilized and euvolemic), and cardiogenic shock.

Relative contraindications: Severe reactive airway disease (asthma, although cardioselective agents may be used cautiously in patients with chronic obstructive pulmonary disease), pheochromocytoma without prior α-blockade (because of the risk of hypertensive crisis from unopposed α-receptor stimulation), insulin-treated diabetes mellitus with recurrent severe hypoglycemia (masking of warning symptoms), severe peripheral arterial disease with critical limb ischemia, and prinzmetal (vasospastic) angina (because of the risk of coronary vasospasm resulting from unopposed α-receptor activation, a risk that is greater with nonselective than with cardioselective.[51]

Loop Diuretics 

Hypersensitivity, severe hepatic encephalopathy, and severe uncontrolled electrolyte depletion.[21]

Mineralocorticoid Receptor Antagonists

Contraindications include serum potassium greater than 5.0 mEq/L at treatment initiation; an eGFR less than 30 mL/min for steroidal mineralocorticoid receptor antagonists (although finerenone has been studied in patients with an eGFR as low as 25 mL/min/1.73 m²); concurrent use of potassium supplements or strong CYP3A4 inhibitors (finerenone).[20][30][32][33][53]

Hydralazine

Contraindications include mitral valve rheumatic heart disease, in which hydralazine may exacerbate pulmonary hypertension; coronary artery disease in the absence of concurrent β-blocker therapy because reflex tachycardia may provoke ischemia); dissecting aortic aneurysm; and known systemic lupus erythematosus or positive antinuclear antibodies because of an increased risk of drug-induced lupus erythematosus. Hydralazine should be used with caution in patients with renal impairment, with dose reduction considered when creatinine clearance is less than 10 mL/min, and in those with cerebrovascular disease.[54]

Central α₂ Agonists

Absolute contraindications: Sick sinus syndrome and second- or third-degree atrioventricular block without a pacemaker.

Relative contraindications: Severe depression, concurrent use with other central nervous system depressants (because of the potential for enhanced sedation), and peripheral vascular disease (which can exacerbate Raynaud phenomenon). Clonidine should not be abruptly discontinued.[55]

Minoxidil

Contraindications include pheochromocytoma (catecholamine surge with reflex activation), pericardial effusion or tamponade, and pulmonary hypertension secondary to mitral stenosis. Minoxidil must be administered in combination with a β-blocker and a loop diuretic; this is an absolute requirement, not optional.[23]

α₁ Antagonists

These are not recommended as monotherapy for hypertension based on evidence from the ALLHAT evidence. These agents should be used cautiously in patients with orthostatic hypotension, hepatic impairment, or concomitant use of phosphodiesterase type 5 inhibitors due to an increased risk of synergistic hypotension.[24]

Monitoring

The 2025 ACC/AHA guideline places home blood pressure monitoring at the center of hypertension management and recommends using validated oscillometric upper-arm devices with cuff sizes appropriately matched to arm circumference.

Protocol: Blood pressure should be measured with the patient seated, feet flat on the floor, back supported, and arm positioned at heart level. After 5 minutes of rest, 2 readings should be obtained at 1-minute intervals in both the morning and evening for at least 3 consecutive days, and preferably for 7 days. Readings obtained on the first day should be discarded, and the remaining measurements averaged.

Home blood pressure monitoring threshold for hypertension: The threshold for diagnosing hypertension using home blood pressure monitoring is an average blood pressure of 130/80 mm Hg or greater. Ambulatory blood pressure monitoring remains the reference standard for confirming hypertension, identifying white-coat and masked hypertension, and evaluating nocturnal dipping patterns. Diagnostic thresholds for ambulatory blood pressure monitoring are a 24-hour average of 125/75 mm Hg or greater, a daytime average of 130/80 mm Hg or greater, and a nighttime average of 110/65 mm Hg or greater.[1]

Drug-Specific Monitoring

Thiazide and loop diuretics: A basic metabolic panel, including sodium, potassium, chloride, bicarbonate, blood urea nitrogen, creatinine, and glucose levels, along with magnesium level, should be obtained at baseline, 2 to 4 weeks after treatment initiation or dosage adjustment, and every 3 to 6 months thereafter. Serum uric acid should be measured at baseline and monitored periodically in patients with a history of gout or hyperuricemia. Serum calcium levels should be monitored in patients receiving thiazide diuretics because hypercalcemia may unmask underlying primary hyperparathyroidism. Patients should also be assessed for signs of volume depletion, including orthostatic vital signs, skin turgor, and mucous membranes, particularly older adults and those experiencing concomitant illness.

Potassium-sparing diuretics and mineralocorticoid receptor antagonists: Potassium levels should be measured at baseline, within 1 week of treatment initiation, at 1 month, at 3 months, and every 3 months thereafter. More frequent monitoring is warranted in patients with CKD, diabetes mellitus, or concomitant use of a renin-angiotensin-aldosterone system inhibitor. Therapy should be withheld if the serum potassium level exceeds 5.5 mEq/L.[21]

Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers: Serum creatinine and potassium levels should be measured at baseline, 1 to 2 weeks after treatment initiation or dosage adjustment, and every 3 to 6 months thereafter. An increase in serum creatinine of up to 30% above baseline is generally expected because of reduced intraglomerular pressure and does not warrant discontinuation of therapy. An increase greater than 30% should prompt evaluation for bilateral renal artery stenosis, volume depletion, or concomitant use of nephrotoxic medications. Patients should be monitored for signs and symptoms of angioedema throughout treatment, as the risk may persist for the duration of therapy. Pregnancy testing should be performed before treatment initiation in women of childbearing potential.[47]

Calcium channel blockers: Patients receiving calcium channel blockers should be monitored for peripheral edema, particularly with dihydropyridine agents, as well as for changes in heart rate and electrocardiographic abnormalities with nondihydropyridine agents, especially when used concomitantly with β-blockers or digoxin. Constipation should be assessed in patients receiving verapamil. Periodic liver function testing is recommended for patients receiving diltiazem or verapamil because of hepatic metabolism and the potential for rare hepatotoxicity. Clinicians should also monitor for clinically significant drug interactions involving CYP3A4 substrates.[46]

β-Blockers: Heart rate and blood pressure should be assessed at each visit. The target resting heart rate is generally 55 to 70 beats per minute; dosage reduction or temporary withholding of therapy should be considered if the heart rate falls below 50 beats per minute and is accompanied by symptoms. Blood glucose should be monitored in patients with diabetes mellitus as β-blockers may impair hypoglycemia awareness. Pulmonary function should be evaluated if respiratory symptoms develop. Patients receiving sotalol require QTc interval monitoring due to the risk of QT prolongation; therapy is typically initiated in an inpatient setting with continuous telemetry monitoring for the first 3 days. Periodic liver function testing is recommended for patients receiving labetalol because of the rare risk of hepatocellular injury.[51]

Mineralocorticoid receptor antagonists and finerenone: Potassium levels should be measured at baseline, 4 weeks after treatment initiation or dosage adjustment, and periodically thereafter. Renal function, including eGFR, should also be monitored. Therapy should be discontinued if the serum potassium concentration exceeds 5.5 mEq/L or if the eGFR declines to less than 15 mL/min/1.73 m².[20][30][32][33][53]

Aprocitentan: Pregnancy testing should be performed before treatment initiation and monthly throughout therapy. Hemoglobin and hematocrit levels should be measured at baseline and monitored periodically because of the risk of dilutional anemia. Liver function tests should be obtained at baseline and repeated periodically during treatment. Patients should also be monitored for fluid retention, peripheral edema, and changes in body weight.[25]

Baxdrostat: Morning serum cortisol levels should be measured at baseline and monitored periodically during treatment. Serum potassium concentrations should also be monitored. Assessment of adrenal function, including a cosyntropin stimulation test, should be performed if there is clinical suspicion of adrenal insufficiency.[27]

Zilebesiran: Blood pressure should be assessed at each healthcare visit because of the prolonged dosing interval of 3 to 6 months. Potassium concentrations should be monitored during follow-up visits. Measurement of angiotensinogen levels may serve as a pharmacodynamic biomarker in clinical practice (not yet part of the standard of care).[37]

Adherence Assessment

The 2025 ACC/AHA guideline emphasizes the assessment of medication adherence before a diagnosis of resistant hypertension is established. Available methods range from self-report questionnaires, such as the Morisky Medication Adherence Scale, which have relatively low sensitivity, to pill counts, pharmacy refill records, and electronic monitoring devices, including medication event monitoring system caps, which are considered the noninvasive reference standard. The most sensitive approach is biochemical verification using high-performance liquid chromatography-tandem mass spectrometry to detect antihypertensive drug metabolites in urine or blood; this method has identified nonadherence in approximately 25% to 50% of patients with apparent resistant hypertension. The guideline recommends a multimodal approach that combines patient communication, pharmacy data, and biochemical verification in refractory cases.[1][57]

Toxicity

Thiazide and Loop Diuretic Toxicity

Overdose manifests as severe electrolyte derangements (hypokalemia, hyponatremia, hypochloremic metabolic alkalosis, and hypomagnesemia) and volume depletion. Management is primarily supportive and includes intravenous isotonic saline for volume repletion, intravenous potassium chloride for hypokalemia, and intravenous magnesium sulfate when indicated. Hypertonic saline (3% sodium chloride) may be required for patients with symptomatic severe hyponatremia. No specific antidote is available.[21][42]

Calcium Channel Blocker Toxicity

Calcium channel blocker overdose is a leading cause of cardiovascular drug–related fatality. Dihydropyridine overdose produces severe hypotension with reflex tachycardia; nondihydropyridine overdose (verapamil, diltiazem) causes the lethal triad of bradycardia, conduction block, and negative inotropy progressing to cardiovascular collapse. Hyperglycemia is characteristic of calcium-dependent impairment of insulin secretion.[58] 

Management follows a stepwise approach:

• Intravenous calcium chloride 10% or calcium gluconate 10%
• High-dose insulin euglycemic therapy
• Intravenous vasopressors (norepinephrine first-line for hypotension; epinephrine for combined inotropic and vasopressor support)
• Intravenous glucagon
• Intravenous lipid emulsion therapy (20% Intralipid 1.5 mL/kg bolus then infusion) for severe cases, particularly with lipophilic calcium channel blockers (eg, verapamil and amlodipine)
• Temporary transvenous pacing for refractory bradycardia
• Extracorporeal membrane oxygenation or cardiopulmonary bypass for refractory cardiogenic shock.

Whole-bowel irrigation is indicated for extended-release formulations. Activated charcoal is indicated if administered within 1 to 2 hours of ingestion.[58]

Angiotensin-Converting Enzyme Inhibitor and Angiotensin II receptor blocker Toxicity

Overdose of ACE inhibitors or ARBs primarily manifests as hypotension and may also result in hyperkalemia and acute kidney injury. Hypotension is often responsive to intravenous crystalloid administration and Trendelenburg positioning; however, refractory cases may require intravenous vasopressors (norepinephrine or vasopressin). Synthetic angiotensin II (marketed as Giapreza) is a direct physiological antidote available for vasodilatory shock refractory to conventional vasopressors.[59] Hyperkalemia management follows standard protocol. No specific antidote exists for ARB overdose, and management remains largely supportive.[47][48]

β-Blocker Toxicity

β-Blocker overdose causes bradycardia, hypotension, cardiogenic shock, and bronchospasm. Propranolol additionally causes seizures (sodium channel blockade) and QRS prolongation. Sotalol overdose is uniquely dangerous because of QT interval prolongation and torsades de pointes.

Treatment includes:

• Intravenous glucagon (first-line antidote)
• High-dose insulin euglycemic therapy
• Intravenous atropine for symptomatic bradycardia
• Intravenous vasopressors (such as norepinephrine or epinephrine at high doses to overcome competitive blockade)
• Temporary transvenous pacing for refractory bradycardia
• Intravenous lipid emulsion therapy for lipophilic agents (eg, propranolol and carvedilol)
• Intravenous sodium bicarbonate for QRS widening with propranolol
• Intravenous magnesium and overdrive pacing for sotalol-induced torsades
• Extracorporeal membrane oxygenation for refractory cardiogenic shock [58]

Mineralocorticoid Receptor Antagonist Toxicity

Mineralocorticoid receptor antagonist toxicity primarily manifests as life-threatening hyperkalemia, which is the leading cause of serious adverse outcomes with this drug class. Hyperkalemia treatment follows standard protocol.[53]

Enhancing Healthcare Team Outcomes

Effective hypertension management requires a coordinated interprofessional approach involving clinicians, pharmacists, nurses, dietitians, and community health workers. The 2025 ACC/AHA guideline emphasizes team-based care models that use the expertise and scope of practice of each healthcare professional to improve blood pressure control.

Pharmacist-led interventions, including medication therapy management, adherence assessments, and collaborative prescribing, have demonstrated significant reductions in blood pressure in randomized clinical trials. Nurse-led titration protocols using standing orders have also been shown to reduce the time to achieve blood pressure targets. In addition, community health workers and digital health technologies, such as remote blood pressure monitoring, telehealth visits, and text-based reminders, can enhance patient engagement and help address social determinants of health that contribute to hypertension-related disparities.

Medication nonadherence remains the leading cause of apparent treatment-resistant hypertension. Studies using biochemical verification methods have identified nonadherence in approximately 25% to 50% of patients with apparent resistant hypertension. Evidence-based strategies to improve adherence include simplifying treatment regimens through single-pill combinations, reducing pill burden, proactively addressing adverse effects, and engaging patients in shared decision-making.