Verapamil

Emergency & Prehospital

• Stable paroxysmal supraventricular tachycardia (PSVT): narrow, regular AV nodal re-entry or orthodromic AV re-entry, including in Wolff-Parkinson-White (WPW) syndrome; FDA-labeled for conversion after vagal maneuvers, usually when adenosine fails, recurs or is unsuitable. AHA 2025 Part 9: IV diltiazem or verapamil can be effective for stable regular narrow-complex tachycardia (COR 2a)
• Atrial fibrillation (AF) or atrial flutter with rapid ventricular response (RVR): hemodynamically stable, no pre-excitation, no decompensated heart failure; FDA-labeled for temporary rate control; AHA 2025 Part 9 Class 1 (COR 1, B-NR) IV rate control with a beta-blocker or nondihydropyridine calcium channel antagonist
• Multifocal atrial tachycardia (off-label): treat the underlying condition first (ESC 2019, Class I); verapamil, diltiazem or a selective beta-blocker should be considered (ESC 2019, Class IIa)

ED / ICU / Transport

• Ongoing AF/flutter rate control: continuous infusion after an effective bolus (off-label; AHA 2025 Part 9, Table 2)
• AF after cardiac surgery: rate control when beta-blockers are ineffective or contraindicated (ACC/AHA 2023)

Other Uses

• Long-term AF rate control and PSVT prevention (oral): FDA-labeled; avoid with LVEF <40%
• Angina (oral): vasospastic (Prinzmetal), unstable and chronic stable angina; FDA-labeled
• Hypertension (oral): FDA-labeled, usually extended-release
• Hypertrophic cardiomyopathy and cluster headache prevention (oral): specialist use (off-label)

Doses vary by protocol; follow local protocols and medical direction. The 2025 AHA Guidelines come first (Part 9, Table 2, for AF/flutter, a weight-based dose), and the FDA label appears wherever it differs. Some EMS protocols start at 2.5–5 mg IV over 2–3 min, then repeat 5–10 mg every 15–30 min, to a total of 20–30 mg. Older patients and anyone with borderline BP often get that smaller first dose. AHA 2025 does not state that regimen.

Available Forms

• Injection: 2.5 mg/mL in 2 mL (5 mg) and 4 mL (10 mg) single-dose vials or ampuls; the form EMS and transport carry. Stored at room temperature, protected from light.
• Oral immediate-release (IR) tablets: 40, 80 and 120 mg.
• Oral extended-release (ER): tablets and capsules (for example 120, 180 and 240 mg tablets) for once-daily use.

Adult Dosing

Pediatric Dosing

Continuous Infusion

Preparation & Administration

• Push: undiluted 2.5 mg/mL as a slow IV injection over at least 2 min (at least 3 min in older patients), then flush.
• Monitoring during the push: continuous ECG and blood pressure; for a first dose, a setting with resuscitation and DC cardioversion available.
• Dilution: it stays stable for at least 24 hr at 25°C (77°F) in most common IV solutions, protected from light. Any solution with a pH above 6.0 makes it precipitate.
• Light: keep vials in the carton until use; discard any unused portion.
• Pump: run any infusion on a smart pump in mg/hr.

The renal and hepatic details are in Special Populations.

Contraindications

• Severe hypotension (SBP <90 mmHg) or cardiogenic shock
• Sick sinus syndrome or 2nd/3rd-degree AV block without a functioning ventricular pacemaker
• AF or atrial flutter with an accessory pathway (WPW or Lown-Ganong-Levine syndrome)
• Ventricular tachycardia (label). AHA 2025 Part 9: verapamil should not be given for any adult wide-complex tachycardia (QRS ≥0.12 s; COR 3: Harm, B-NR); SVT with known aberrancy is a specialist decision only
• IV beta-blocker given at the same time or within a few hours
• Decompensated heart failure or LV systolic dysfunction: AHA 2025 Part 9 says do not use (COR 3: Harm, C-EO); not preferred in suspected systolic heart failure
• Hypersensitivity to verapamil

Precautions

• Older adults and sick sinus disease: bradycardia and asystole are more likely in this group. Push over at least 3 min.
• Hypertrophic cardiomyopathy with severe outflow obstruction: pulmonary edema, severe hypotension and deaths have all been reported. For hypotension in HCM, reach for an alpha-agonist such as phenylephrine. Avoid isoproterenol and norepinephrine (label).
• Oral beta-blocker: the effects stack. Bradycardia, AV block and negative inotropy all add up. Avoid it with any degree of LV dysfunction or an AV conduction abnormality (oral label). Otherwise, monitor closely.
• Duchenne muscular dystrophy: IV verapamil can tip the respiratory muscles into failure. Myasthenia gravis: it can make the weakness worse. In both, use caution, lower the doses and watch their ventilation.
• Raised intracranial pressure: in patients with supratentorial tumors, IV verapamil raised ICP at anesthesia induction.
• AF/flutter rarely converts: only about 10% convert to sinus rhythm after IV verapamil, much like placebo. If AF has lasted more than 48 hr or the onset is unknown, sort out anticoagulation before any planned cardioversion.

Hold / Reassess If

• SBP <90 mmHg or symptomatic hypotension: stop; fluids; see Reversal
• Symptomatic bradycardia, pauses or asystole beyond a few seconds: stop; atropine and pacing ready
• New 2nd/3rd-degree AV block or new bundle branch block: reduce or stop further doses
• QRS widens or the rhythm turns irregular and broad: stop; reassess for pre-excitation or VT
• New crackles, rising O₂ need or falling perfusion: stop; treat heart failure

Common

• IV: asymptomatic fall in BP (SBP <90 or DBP <60 mmHg) in 5–10% with SVT and about 10% with AF/flutter
• IV: symptomatic hypotension 1.5%, bradycardia 1.2%, dizziness 1.2%, headache 1.2%, nausea 0.9%
• IV: a few benign, odd-looking complexes during conversion that resemble premature ventricular contractions
• Oral: constipation 7.3%, dizziness 3.3%, nausea 2.7%, hypotension 2.5%, edema 1.9%, heart failure or pulmonary edema 1.8%

Serious / Life-Threatening

Overdose & Toxicity Management

• Signs: hypotension, bradycardia, AV block, cardiogenic or vasodilatory shock, asystole; hyperglycemia (higher glucose tracks severity). With extended-release tablets, the toxicity can be delayed and prolonged.
• Vasopressors (COR 1, C-LD): norepinephrine and/or epinephrine for hypotension. Vasopressin, angiotensin II, milrinone and hydroxocobalamin lack the evidence to support them (AHA 2025 Part 10).
• High-dose insulin (COR 1, B-NR) for hypotension: insulin 1 unit/kg IV, then 1–10 units/kg/hr with dextrose and K⁺ checks; protocolized care reduces hypoglycemia.
• Calcium (COR 2a, C-EO): calcium chloride 2 g (20 mL of 10%) IV, or calcium gluconate 6 g; then calcium chloride 20–40 mg/kg/hr (0.2–0.4 mL/kg/hr) or calcium gluconate 60–120 mg/kg/hr, titrated to blood pressure. Do not exceed an ionized calcium 1.5–2 times the upper limit of normal. Give chloride through a central line when possible; calcium gluconate if peripheral. See the calcium chloride page.
• Pediatric calcium chloride: 20 mg/kg (0.2 mL/kg) slowly IV over 10 min; max 1 g or 10 mL. Calcium gluconate 60 mg/kg over 10 min is preferred in children because chloride carries more tissue-injury risk. Differs: AHA 2025 Table 4 allows up to the adult 2 g, and an infusion of 20–40 mg/kg/hr.
• Glucagon (COR 2b, C-EO): 2–10 mg IV (children 0.05–0.15 mg/kg), then 1–15 mg/hr; usefulness uncertain. Plan for vomiting.
• Methylene blue (COR 2b, C-EO): refractory vasodilatory shock: 1–2 mg/kg IV, repeated hourly if needed; 1 mg/kg/hr infusion; maximum 5–7 mg/kg.
• Lipid emulsion (COR 2b, C-EO): usefulness uncertain; not routine.
• Atropine and pacing: for symptomatic bradycardia or high-grade block (standard ALS; not a Part 10 recommendation).
• Cardiac arrest: calcium is reasonable (COR 2a); VA-ECMO is reasonable for refractory cardiogenic shock or arrest (COR 2a: adults B-NR, children C-LD).
• Refractory: transcutaneous pacing for unstable bradycardia or high-grade block; VA-ECMO where available.
• Observation and removal: activated charcoal may be considered within 1 hr of ingestion; Adult consensus: observe asymptomatic patients who took more than one therapeutic dose for about 24 hr in hospital. The FDA oral label says to treat every verapamil overdose as serious and to observe for at least 48 hr, especially with sustained-release forms, because toxicity can be delayed. Follow poison control or toxicology. Not removed by hemodialysis. Call poison control (1-800-222-1222).

Clinically Significant Interactions

IV Compatibility

• Diluents: it stays stable for 24 hr at 25°C, protected from light, in most common large-volume IV solutions.
• Precipitates: it precipitates in any solution with a pH above 6.0. Flush well between verapamil and alkaline drugs.
• Do not admix with: albumin, amphotericin B, hydralazine or trimethoprim-sulfamethoxazole; not recommended in sodium lactate in PVC bags.
• Verify with an institutional compatibility resource.

• Pediatrics: there are no controlled studies. Specialist use only, and not routinely in infants because of fatal collapse. See the Pediatric Dosing block.
• Neonates: avoid it. Fatal hemodynamic reactions have been reported.
• Pregnancy: there are no adequate human studies. Animal studies showed no birth defects, but fetal harm appeared at maternally toxic doses. It crosses the placenta. For rate control in pregnancy, ACC/AHA prefer beta-blockers or digoxin. Electrical cardioversion is safe for mother and fetus. In an emergency, treat the mother.
• Lactation: it is excreted in breast milk. The label advises against breastfeeding during therapy. Discuss timing and alternatives with pharmacy.
• Older Adults: the half-life is prolonged, and sick sinus disease is more common. Push IV doses over at least 3 min, and start oral doses low. AGS Beers Criteria 2023 says to avoid nondihydropyridine calcium channel blockers in heart failure with reduced ejection fraction (HFrEF).
• Renal Impairment: a single IV dose may last longer. Repeat injections can build up, so avoid them or give smaller doses while you watch BP and PR. Hemodialysis does not remove it.
• Hepatic Impairment: apply the same IV caution as in renal impairment. Severe liver dysfunction stretches the oral half-life to 14–16 hr, so give about 30% of the usual oral dose.
• Obesity / Dosing Weight: AHA 2025 Table 2 dosing is weight-based (0.075–0.15 mg/kg). It does not state actual or ideal body weight, so the weight basis is unspecified. The FDA label uses a fixed 5–10 mg IV. Above about 67 kg, the upper weight-based dose exceeds 10 mg. Titrate to response and reassess before any repeat.
• Heart Failure: AHA 2025 Part 9 (COR 3: Harm, C-EO) says do not use it with LV systolic dysfunction and decompensated heart failure. It is not preferred in suspected systolic heart failure.

• Scope: usually paramedic and critical-care transport, per local protocol. State and agency protocols vary.
• Storage & Stability: keep it at 20–25°C (68–77°F) in the carton, protected from light. It does not need refrigeration. Avoid prolonged heat or freezing in the vehicle.
• Carried Concentration: 2.5 mg/mL only (5 mg/2 mL and 10 mg/4 mL). Draw up by mg, and confirm the volume before you push.
• Infusions in Transport: run it on a smart pump in mg/hr, on a dedicated line, with enough volume for the trip. Confirm the rate (mg/hr and mg/kg/min) and the start time at handoff. Above about 67 kg, the weight-based rate exceeds 20 mg/hr.
• Handoff Essentials: rhythm strip before and after, each dose and time, HR and BP response, any hypotension treatment, beta-blocker or digoxin use, AF onset time, anticoagulant use and known LVEF.

Mechanism of Action

• L-type Ca²⁺ channel block in the SA and AV nodes: AV conduction slows, and the AV-nodal refractory period lengthens in a rate-dependent way. That gives ventricular rate control in AF/flutter and termination of AV-nodal re-entry.
• Does not slow accessory pathways or the His bundle: it has no effect on His bundle fibers. It may shorten the accessory pathway's antegrade refractory period, which is how pre-excited AF can speed up.
• Myocardium and vessels: it lowers contractility and afterload. Cardiac index is usually maintained, but heart failure can worsen with LVEF <30%.

Pharmacokinetics

• Half-life: IV: distribution about 4 min, terminal 2–5 hr. Oral: 2.8–7.4 hr after a single dose, 4.5–12 hr with repeated dosing; longer in older adults and 14–16 hr in severe liver disease.
• Metabolism: the liver does extensive first-pass metabolism (CYP3A4 and others). Oral bioavailability is 20–35%. Verapamil also inhibits CYP3A4 and P-glycoprotein.
• Active metabolites: norverapamil carries about 20% of the parent's cardiovascular activity, and it reaches similar levels with chronic oral use.
• Elimination: about 70% in urine and 16% in feces as metabolites; 3–4% unchanged. Not dialyzable.
• Protein binding: about 90%.

Generic Name

Verapamil hydrochloride

Brand Names

Calan, Calan SR, Isoptin SR, Verelan, Verelan PM (US availability varies; most supply is generic); Tarka (with trandolapril); injection sold as generic

Pharmacologic Class

Nondihydropyridine (phenylalkylamine) calcium channel blocker; Vaughan Williams class IV

Therapeutic Class

Antiarrhythmic (AV-nodal rate control); antianginal; antihypertensive

Controlled Substance

Not controlled

ISMP High-Alert

Yes: ISMP high-alert medication (antiarrhythmics, IV); verapamil is not a named example

Look-Alike / Sound-Alike

Check the current ISMP confused-drug-names list; dose by mg, not mL (2.5 mg/mL in 2 mL and 4 mL containers)