Verapamil
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Essential hypertension | Adults | Monotherapy or combination (oral SR/ER) | FDA Approved |
| Chronic stable angina | Adults | Monotherapy or with nitrates (oral) | FDA Approved |
| Vasospastic angina (Prinzmetal) | Adults | Monotherapy (oral) | FDA Approved |
| Unstable angina (crescendo, preinfarction) | Adults | Adjunctive (oral) | FDA Approved |
| SVT / PSVT | Adults & children (≥1 yr, IV only) | Acute conversion (IV); prophylaxis (oral) | FDA Approved |
| Atrial fibrillation / flutter — rate control | Adults | Acute IV rate control | FDA Approved |
Verapamil is the prototypical phenylalkylamine calcium channel blocker with the broadest FDA-approved indication profile among CCBs. It exerts the strongest negative inotropic and dromotropic effects of all calcium channel blockers, making it particularly effective for supraventricular arrhythmias but also requiring the most caution regarding cardiac depression. Its local anesthetic potency (1.6 times that of procaine on an equimolar basis) and reduction of GI transit time (causing its signature constipation side effect) further distinguish it from other CCB subclasses. Verapamil does not induce bronchoconstriction and can be used safely in patients with asthma, unlike beta-blockers.
Migraine prophylaxis — supported by AAN guidelines as a Level B preventive agent; typical dose 240–480 mg/day (Evidence: Moderate)
Cluster headache prophylaxis — considered first-line preventive therapy; typical dose 240–960 mg/day (Evidence: Moderate)
Hypertrophic cardiomyopathy (HCM) — used to reduce outflow tract gradient and improve diastolic filling; doses up to 720 mg/day have been studied (Evidence: Moderate)
Chronic oral AF/AFL rate control — ACC/AHA/HRS guideline first-line rate-control agent; 240–480 mg/day divided (Evidence: High)
Dosing
Adult Oral Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Hypertension — SR/ER (Calan SR, Isoptin SR, Verelan) | 180 mg QAM (Calan SR); 120 mg QAM (Verelan) | 240–480 mg/day | 480 mg/day | Titrate at weekly intervals; Calan SR: take with food; Verelan: may open capsule and sprinkle on applesauce Calan SR PI starts at 180 mg; 120 mg for elderly or small patients. Verelan PI starts at 120 mg (usual dose 240 mg). |
| Hypertension — bedtime ER (Verelan PM) | 100 mg QHS | 200–300 mg QHS | 400 mg/day | Designed for bedtime dosing with controlled onset during early AM hours |
| Hypertension — bedtime ER (Covera-HS) | 180 mg QHS | 180–480 mg QHS | 480 mg/day | Covers early morning BP surge; score line allows halving if needed |
| Chronic stable / vasospastic angina — IR | 80–120 mg TID | 240–480 mg/day divided TID | 480 mg/day | Titrate at daily or weekly intervals based on angina response; optimal in most patients at 320–480 mg/day |
| AF/AFL — chronic oral rate control (off-label) | 120–240 mg/day divided TID-QID (IR) or SR once-twice daily | 240–480 mg/day | 480 mg/day | First-line rate-control per ACC/AHA/HRS; target resting HR <110 bpm (lenient) or <80 bpm (strict) |
| PSVT prophylaxis (oral) | 240–480 mg/day divided TID-QID | Per response | 480 mg/day | For recurrent PSVT when acute IV therapy has been successful |
IV Dosing — Acute Arrhythmia Management
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| SVT / PSVT / AF/AFL — adults | 2.5–5 mg IV over ≥2 min | 5–10 mg IV after 15–30 min if needed | 20 mg total | Continuous ECG and BP monitoring mandatory; initial bolus should not exceed 5 mg Administer over ≥3 min in elderly patients |
| SVT — children 1–15 years | 0.1–0.3 mg/kg IV over ≥2 min | Repeat once after 30 min if needed | 5 mg (initial); 10 mg (repeat) | Do not exceed 5 mg initial dose; pediatric IV use is FDA-approved for ≥1 year |
Special Population Dosing
| Population | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Hepatic impairment | Reduce to ~30% of usual dose | Individualize | Reduced | Half-life prolonged to 14–16 h; clearance reduced to ~30% of normal; monitor PR interval closely |
| Renal impairment | Standard; use caution | Monitor for toxicity | Standard | Monitor PR interval and signs of overdosage; verapamil is not significantly dialyzable |
| Elderly | Lower end of range | Titrate cautiously | Standard | Elimination half-life may be prolonged; greater sensitivity to conduction effects; IV bolus over ≥3 min |
Among the non-dihydropyridine CCBs, verapamil has stronger negative inotropic effects and a higher incidence of constipation (7.3% vs 2–3% with diltiazem), while diltiazem has less impact on cardiac contractility. For patients with borderline LV function who need a non-dihydropyridine CCB, diltiazem is generally preferred. However, verapamil has more robust data for cluster headache prophylaxis and hypertrophic cardiomyopathy. Both drugs are equally effective for SVT conversion and AF/AFL rate control, with similar AV nodal blocking potency at therapeutic doses.
Pharmacology
Mechanism of Action
Verapamil binds to the intracellular surface of L-type voltage-gated calcium channels at the phenylalkylamine binding site, which is distinct from both the dihydropyridine binding site (used by nifedipine, amlodipine) and the benzothiazepine site (used by diltiazem). This binding inhibits transmembrane calcium influx in vascular smooth muscle, cardiac myocytes, and the cardiac conduction system. Verapamil exerts the most pronounced negative inotropic (reduced contractility), chronotropic (reduced heart rate), and dromotropic (slowed AV conduction) effects of any calcium channel blocker. It reduces systemic vascular resistance, coronary artery tone, and myocardial oxygen demand. Its strong AV nodal blockade makes it highly effective for terminating and preventing re-entrant supraventricular tachycardias. Verapamil also possesses local anesthetic activity approximately 1.6 times that of procaine and decreases gastrointestinal transit time, explaining the high incidence of constipation. Importantly, verapamil does not cause bronchoconstriction and can be safely used in patients with reactive airway disease.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | >90% absorbed from GI tract; bioavailability 20–35% due to extensive first-pass hepatic metabolism; IR Tmax 1–2 h; Calan SR Tmax ~5–8 h; food with Calan SR reduces AUC but narrows peak-to-trough ratio | Low bioavailability amplifies CYP3A4 interaction magnitude. Calan SR should be taken with food for smoother absorption. Non-linear pharmacokinetics: dose-disproportionate increases in exposure at higher doses. |
| Distribution | Protein binding ~90%; 12 identified plasma metabolites; norverapamil is the main active metabolite (~20% activity, levels approximately equal to parent at steady state) | High protein binding limits dialysis efficacy. Norverapamil contributes clinically to both therapeutic and adverse effects, particularly at steady state. |
| Metabolism | Extensive hepatic metabolism via CYP3A4 (primary), CYP1A2, CYP2C; verapamil is both a substrate and moderate inhibitor of CYP3A4 and P-gp | Bidirectional interaction potential: verapamil levels are raised by CYP3A4 inhibitors and reduced by inducers, while verapamil itself raises levels of many CYP3A4 substrates. Hepatic impairment: t½ 14–16 h, clearance ~30% of normal. |
| Elimination | ~70% urine, ~16% feces (as metabolites); 3–4% unchanged in urine; t½ 6–8 h (single dose), increases with repeat dosing; not significantly removed by hemodialysis | Repeated dosing leads to accumulation and prolongation of effects, particularly in hepatic or renal impairment. PR interval prolongation correlates with plasma verapamil concentration during early titration. |
Side Effects
Adverse effect data below are from pooled clinical trial experience with oral verapamil formulations (N=4,954 patients). Constipation is the hallmark side effect of verapamil, occurring at substantially higher rates than with diltiazem or any dihydropyridine CCB.
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Constipation | 7.3% | Signature verapamil side effect; caused by reduced GI smooth muscle motility via calcium channel blockade; dose-related; manage with increased fibre, hydration, and stool softeners; typically mild and easily manageable |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Dizziness | 3.3% | Related to BP lowering and possible cardiac output reduction; advise slow position changes |
| Nausea | 2.7% | Usually mild; may improve with food intake for IR formulations |
| Hypotension | 2.5% | More common during initial titration; 1.7% in Verelan PM trials; potentiated by concurrent antihypertensives |
| Headache | 2.2% | Paradoxical given verapamil’s use in migraine prophylaxis; usually transient |
| Peripheral edema | 1.9% | Less common than with dihydropyridines; localized vasodilatory mechanism |
| CHF / pulmonary edema | 1.8% | Reflects significant negative inotropy; higher risk in patients with pre-existing LV dysfunction |
| Fatigue | 1.7% | Related to reduced cardiac output and heart rate |
| Bradycardia (HR <50) | 1.4% | Expected pharmacologic effect; more common in sick sinus syndrome (0.3% in double-blind trials); dose-related |
| AV block (all degrees) | 1.2% | First-degree: 0.35%; second/third-degree: 0.8%; higher degrees are rare but require dose reduction or discontinuation |
| Rash | 1.2% | Monitor for progression; rare cases of SJS and erythema multiforme reported post-marketing |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| CHF / pulmonary edema | 1.8% | Weeks to months; higher risk with impaired LV function | Discontinue verapamil; standard heart failure management; avoid in severe LV dysfunction |
| Second/third-degree AV block | 0.8% | Early titration; higher risk with sick sinus syndrome | Hold verapamil; atropine for acute episodes; may require temporary pacing; absolute CI without pacemaker |
| Asystole | Very rare | Usually brief (seconds); more common with sick sinus syndrome | Usually self-terminating; if prolonged: CPR, atropine, isoproterenol, IV calcium, pacing |
| Rapid ventricular rate (WPW/accessory pathway) | Very rare but life-threatening | Minutes after IV administration in AF with WPW | DC cardioversion immediately; verapamil absolutely contraindicated in AF/AFL with accessory pathway |
| Hepatocellular injury | Rare | Weeks to months; proven by rechallenge in several cases | Check LFTs; discontinue if significant elevation; half of reported cases had clinical symptoms (malaise, fever, RUQ pain) |
| Paralytic ileus | Rare | Variable; related to GI hypomotility | Discontinue; supportive GI management; distinguish from mechanical obstruction |
Constipation is the most common side effect unique to verapamil among CCBs. It results from calcium channel blockade in GI smooth muscle, reducing peristalsis. Proactive management is recommended from initiation: increased dietary fibre (25–30 g/day), adequate fluid intake (1.5–2 L/day), and regular physical activity. Osmotic laxatives (polyethylene glycol) or stool softeners (docusate) may be used if dietary measures are insufficient. If constipation is severe or if paralytic ileus develops, consider switching to diltiazem (which causes constipation at a much lower rate) or to a dihydropyridine CCB.
Drug Interactions
Verapamil is both a substrate and moderate inhibitor of CYP3A4, CYP1A2, CYP2C, and P-glycoprotein. Combined with its potent cardiac depressant properties, verapamil has one of the most extensive drug interaction profiles among cardiovascular medications. Particular vigilance is required with drugs that affect cardiac conduction, contractility, or are CYP3A4 substrates with narrow therapeutic indices.
Monitoring
- Blood PressureBaseline, each titration, regularly
RoutineMonitor seated and standing. Verapamil can cause symptomatic hypotension (2.5% in trials). Close surveillance during initial titration and when adding concurrent antihypertensives. - Heart Rate & ECGBaseline, each titration, periodically
RoutinePR interval prolongation correlates with verapamil plasma concentration during early titration. ECG mandatory before initiation and during IV administration. Monitor for bradycardia, AV block, and widening PR interval. - Liver Function TestsPeriodically; trigger-based
RoutineFDA PI recommends periodic LFT monitoring. Hepatocellular injury has been proven by rechallenge in several cases. Check if jaundice, malaise, fever, or RUQ pain develops. - Bowel FunctionEach visit
RoutineConstipation occurs in 7.3% of patients. Proactively assess and manage. Rare cases of paralytic ileus reported; evaluate any new-onset abdominal distension or vomiting. - Digoxin LevelsAt initiation and dose changes
Trigger-basedVerapamil increases digoxin levels 50–75%. Reduce digoxin dose empirically and monitor levels closely. - Signs of Heart FailureEach visit
RoutineCHF/pulmonary edema occurred in 1.8% of patients. Assess for dyspnea, weight gain, JVD, peripheral edema. Risk higher when combined with beta-blockers or in patients with impaired LV function.
Contraindications & Cautions
Absolute Contraindications
- Severe left ventricular dysfunction (unless HF is secondary to a supraventricular arrhythmia amenable to verapamil)
- Hypotension (systolic BP <90 mmHg) or cardiogenic shock
- Sick sinus syndrome without a functioning ventricular pacemaker
- Second- or third-degree AV block without a functioning ventricular pacemaker
- Atrial fibrillation/flutter with an accessory bypass tract (WPW, LGL) — risk of ventricular fibrillation
- Known or suspected ventricular tachycardia — administration may cause hemodynamic collapse
- Concurrent IV beta-blocker (for IV verapamil) — severe bradycardia, AV block, asystole, or cardiac arrest
- IV dantrolene — cardiovascular collapse and hyperkalemia (contraindicated)
- Hypersensitivity to verapamil or other CCBs
Relative Contraindications (Specialist Input Recommended)
- Moderate LV dysfunction (EF 30–40%) — negative inotropic effect may precipitate or worsen heart failure
- Wide-complex tachycardia of uncertain origin — if the rhythm is VT, verapamil can cause cardiovascular collapse
- Moderate to severe hepatic impairment — clearance reduced to ~30%, dramatically prolonged half-life
- Neuromuscular diseases (e.g., myasthenia gravis, Duchenne muscular dystrophy) — may worsen neuromuscular transmission
Use with Caution
- Hypertrophic cardiomyopathy — higher adverse event rates documented (deaths, pulmonary edema, hypotension) at doses up to 720 mg/day in a 120-patient study
- Concurrent oral beta-blockers — additive cardiac depression; use only with close monitoring
- Concurrent digoxin — levels increase 50–75%; reduce digoxin dose proactively
- Elderly patients — prolonged half-life; greater sensitivity to negative chronotropic and dromotropic effects
A small fraction (<1%) of patients treated with IV verapamil may develop life-threatening adverse responses. In patients with atrial fibrillation or flutter and an accessory AV pathway (WPW syndrome, LGL syndrome), verapamil can paradoxically accelerate conduction down the accessory pathway, resulting in a rapid ventricular response that may degenerate into ventricular fibrillation. IV verapamil should only be administered in settings with monitoring, resuscitation facilities, and DC cardioversion capability. Before administering IV verapamil for a wide-complex tachycardia, the arrhythmia must be confirmed as supraventricular in origin.
Patient Counselling
Purpose of Therapy
Verapamil is prescribed to lower blood pressure, prevent chest pain (angina), or control heart rhythm. It works by relaxing blood vessels and slowing the heart’s electrical signals. For blood pressure and angina, daily use provides ongoing protection. For heart rhythm problems, it helps keep the heart beating at a normal, steady rate.
How to Take
Immediate-release tablets are taken two to three times daily. Extended-release tablets or capsules (SR, ER, PM) are taken once or twice daily depending on the formulation. Some formulations (Calan SR) should be taken with food; others (Verelan PM, Covera-HS) are taken at bedtime. Never crush or chew extended-release products. Verelan capsules may be opened and sprinkled on a spoonful of applesauce; swallow immediately without chewing.
Sources
- Calan (verapamil HCl) Tablets. Full Prescribing Information. Pfizer Inc. Revised 2017. accessdata.fda.gov FDA label for IR tablets (Calan); source of angina/HTN dosing, PK data, adverse effect incidence (N=4,954), and drug interactions.
- Calan SR (verapamil HCl) Sustained-Release Tablets. Full Prescribing Information. Pfizer Inc. Revised 2020. accessdata.fda.gov FDA label for SR tablets; source of HTN dosing, SR-specific PK (food effect, Tmax), and formulation-specific guidance.
- Verelan PM (verapamil HCl) Extended-Release Capsules. Full Prescribing Information. Revised 2011. accessdata.fda.gov FDA label for bedtime ER capsules; source of Verelan PM dosing, hypotension incidence (1.7%), and comprehensive adverse event tables.
- Calan (verapamil HCl) for Intravenous Injection. Full Prescribing Information. Revised 2016. accessdata.fda.gov FDA label for IV formulation; source of IV bolus dosing, pediatric dosing, accessory pathway warnings, and acute adverse reaction management.
- The Danish Verapamil Infarction Trial II (DAVIT-II). Effect of verapamil on mortality and major events after acute myocardial infarction. Am J Cardiol. 1990;66(10):779-785. doi:10.1016/0002-9149(90)90351-Z RCT showing verapamil reduced mortality and reinfarction rate in post-MI patients without heart failure, establishing role in selected secondary prevention.
- Pepine CJ, Handberg EM, Cooper-DeHoff RM, et al. A calcium antagonist vs a non-calcium antagonist hypertension treatment strategy for patients with coronary artery disease: the INVEST randomized controlled trial. JAMA. 2003;290(21):2805-2816. doi:10.1001/jama.290.21.2805 Major outcomes trial (22,576 patients) demonstrating verapamil-trandolapril strategy was equivalent to atenolol-HCTZ strategy for cardiovascular events in hypertensive CAD patients.
- Whelton PK, Carey RM, Aronow WS, et al. 2017 ACC/AHA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. Hypertension. 2018;71(6):e13-e115. doi:10.1161/HYP.0000000000000065 Current US hypertension guideline; non-DHP CCBs are second-line for HTN but first-line for concurrent rate control needs in AF.
- January CT, Wann LS, Calkins H, et al. 2019 AHA/ACC/HRS focused update of the 2014 guideline for management of patients with atrial fibrillation. Circulation. 2019;140(2):e125-e151. doi:10.1161/CIR.0000000000000665 Guideline recommending verapamil and diltiazem as first-line rate-control agents for AF in patients without HFrEF.
- Silberstein SD, Holland S, Freitag F, et al. Evidence-based guideline update: pharmacologic treatment for episodic migraine prevention in adults. Neurology. 2012;78(17):1337-1345. doi:10.1212/WNL.0b013e3182535d20 AAN guideline classifying verapamil as a Level B (probably effective) agent for episodic migraine prevention.
- Hockerman GH, Peterson BZ, Johnson BD, Catterall WA. Molecular determinants of drug binding and action on L-type calcium channels. Annu Rev Pharmacol Toxicol. 1997;37:361-396. doi:10.1146/annurev.pharmtox.37.1.361 Definitive review of L-type calcium channel binding pharmacology; describes verapamil’s phenylalkylamine binding site distinct from dihydropyridine and benzothiazepine sites.
- Abernethy DR, Schwartz JB, Todd EL, Luchi R, Snow E. Verapamil pharmacodynamics and disposition in young and elderly hypertensive patients. Ann Intern Med. 1986;105(3):329-336. doi:10.7326/0003-4819-105-3-329 Key PK study demonstrating increased verapamil sensitivity in elderly patients with prolonged half-life and greater ECG effects at comparable plasma levels.
- McAllister RG Jr, Hamann SR, Blouin RA. Pharmacokinetics of calcium-entry blockers. Am J Cardiol. 1985;55(3):30B-40B. doi:10.1016/0002-9149(85)90609-3 Comparative PK review of calcium channel blockers establishing verapamil’s non-linear kinetics, extensive first-pass metabolism, and norverapamil pharmacology.
- Fahie S, Cassagnol M. Verapamil. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2026. Updated February 6, 2023. ncbi.nlm.nih.gov Comprehensive overview of verapamil pharmacology, dosing across formulations, adverse effects, drug interactions, and clinical monitoring.