Generic Name

Mechanism of Action

Mechanism

• Verapamil is a dihydropyridine calcium channel blocker that selectively inhibits L‑type calcium channels in vascular smooth muscle, cardiac myocytes, and the sinoatrial (SA) node.
• By reducing calcium influx, it causes vasodilation, decreases myocardial contractility, and slows AV‑node conduction.
• The net effect is a reduction in systemic blood pressure, attenuation of atrial fibrillation/atrial flutter, and control of ventricular tachyarrhythmias.

Pharmacokinetics

• Absorption: Oral bioavailability ~30 – 40 % due to extensive first‑pass metabolism.
• Distribution: Highly protein‑bound (> 70 % to albumin). Crosses the placenta; not excreted in breast milk.
• Metabolism: Primarily hepatic via CYP3A4, with minor CYP2D6 contribution.
• Elimination: Half‑life 3 – 6 h (oral); 15 – 18 h (intravenous). Renally excreted 10–20 % unchanged.
• Drug interactions: CYP3A4 inhibitors (ketoconazole, clarithromycin) ↑ plasma levels; CYP3A4 inducers (rifampin, carbamazepine) ↓ efficacy.

Indications

• Hypertension: oral or IV to lower systolic BP.
• Arrhythmias:
• Atrial fibrillation/flutter – control ventricular response.
• Ventricular tachycardia – convert paroxysmal episodes.
• Angina (stable, variant): vasodilator effect reduces ischemia.
• Hypertrophic cardiomyopathy: decreases subaortic gradient.
• Post‑coronary bypass: reduces incidence of restenosis (in select settings).

Contraindications

• Contraindications:
• Severe bradycardia or AV nodal block (unless pacing device present).
• Hypotension (SBP < 90 mmHg).
• Recent myocardial infarction with LV dysfunction.
• Warnings:
• Liver dysfunction → ↑ exposure.
• Heart failure → negative inotropy may worsen symptoms.
• Drug‑drug interactions with CYP3A4 inhibitors/inducers.

Dosing

• Special populations: Reduce dose in severe renal or hepatic impairment; consider lower starting dose with diuretic‑induced hypotension.

Adverse Effects

• Common (≥ 5 %)
• Peripheral edema
• Flushing
• Headache
• Nausea, vomiting
• Constipation
• Serious (≤ 5 %)
• Bradycardia / AV block
• Severe hypotension
• Acute heart failure
• QTc shortening (rare)
• Hepatotoxicity (rare, monitor LFTs)

Monitoring

• Vital signs: BP & HR at baseline, after first dose, and weekly for first month.
• ECG: baseline, after loading dose, and if symptomatic.
• Laboratory tests: LFTs, electrolytes (K⁺, Mg²⁺) at baseline and monthly while on therapy.
• Renal function: eGFR (baseline, every 3 months).
• Patient education: advise against alcohol and concomitant antihypertensives unless physician‑directed.

Clinical Pearls

• Peri‑operative use: Start verapamil a few days before surgery; give a loading IV dose only if SBP > 140 mmHg; avoid intra‑operative bolus in patients with a pacemaker to prevent sudden AV block.
• Combination with β‑blockers: Using both can potentiate negative inotropy; monitor for conduction delay.
• Alternative routes: IV verapamil is preferred for acute ventricular arrhythmias; oral succinate is excellent for chronic hypertension with fewer side‑effects than infusions.
• Fasting absorption: Oral absorption is optimal after a meal; fasting can reduce oral bioavailability.
• Drug‑interaction flag: Ketoconazole can increase verapamil levels by 5‑fold; patients on this antifungal need dose adjustment or close monitoring.

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• *Prepared for medical students and healthcare professionals seeking a concise, SEO‑friendly reference on verapamil.*