Prescription ·Strong evidence ·Reviewed May 2026
Verapamil is a phenylalkylamine-type non-dihydropyridine calcium channel blocker with the strongest negative inotropic and chronotropic effects among CCBs. It is used for hypertension, angina, supraventricular tachyarrhythmias, and migraine prophylaxis.
The bottom line
Evidence rating strong. Most-documented uses: effective rate control in supraventricular tachyarrhythmias, blood pressure reduction, angina relief. 10 sources indexed (2011–2026), with 5 interaction records on file.
Core mechanism
Inhibits L-type calcium channels, with preferential binding to cardiac tissue compared to vascular smooth muscle. Strongly slows SA and AV nodal conduction, reduces heart rate, decreases contractility, and causes moderate vasodilation. Terminates reentrant SVTs by blocking AV nodal conduction. Also used for cluster headache and migraine prophylaxis.1,5
Take with food to reduce GI side effects; sustained-release formulations should not be crushed
St. John's Wort induces CYP3A4, the primary enzyme metabolizing verapamil. This can reduce verapamil levels by 40-80%, leading to loss of heart rate/blood pressure control and breakthrough arrhythmias.
Recommendation: Avoid St. John's Wort with verapamil. Loss of rate control can be dangerous in atrial fibrillation patients.
Both verapamil and magnesium block calcium channels. Combined use can cause excessive bradycardia, hypotension, and AV conduction delay.
Recommendation: Use low-dose magnesium (200mg) with verapamil. Monitor heart rate and BP. Avoid if heart rate <55 bpm.
Verapamil is both a CYP3A4 substrate and a potent P-glycoprotein inhibitor, and berberine inhibits both CYP3A4 and P-gp. Combining the two raises verapamil exposure and slows its clearance, which can trigger bradycardia, AV block, hypotension, or constipation. Because berberine itself is a P-gp substrate, verapamil also raises berberine systemic levels.
Recommendation: Avoid combining berberine with verapamil. If your clinician approves co-use, monitor pulse and blood pressure daily for the first 2 weeks, and report HR below 50 bpm, dizziness, or new constipation. Separate doses by at least 4 hours to limit intestinal interaction.
In rabbits, quercetin roughly doubled both the Cmax and AUC of verapamil by inhibiting CYP3A4 and P-glycoprotein. Verapamil already has a narrow therapeutic window for bradycardia and AV block, so high-dose quercetin supplements layered onto verapamil could meaningfully amplify rate suppression, hypotension, or constipation.
Recommendation: Avoid high-dose quercetin supplements (over 500 mg/day) while on verapamil. If used, separate doses by at least 4 hours, monitor pulse and blood pressure twice daily for 2 weeks, and stop quercetin if your HR drops below 50 bpm or you become lightheaded.
Taurine lowers systolic and diastolic blood pressure by about 3-4 mmHg in meta-analysis and has direct heart-rate-lowering effects. Combined with verapamil's strong rate and AV-node suppression, taurine can push heart rate or blood pressure too low, especially in older adults or those on additional rate-slowing drugs.
Recommendation: If you take verapamil, taurine doses up to 1.5-3 g/day are usually tolerable, but check your blood pressure and resting heart rate when you start. Reduce or stop taurine if your HR drops below 50 bpm or you develop new dizziness or fatigue.
Numbered references. Citations throughout the page link here.
Tu S, Zhang R, Zheng Q et al.. Effect of Verapamil on Blood Glucose in Type 1 and Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis. Cardiovascular drugs and therapy. 2026
Collins L, Lam L, Kleinig O et al.. Verapamil in the treatment of reversible cerebral vasoconstriction syndrome: A systematic review. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia. 2023
Taha M, Dahat P, Toriola S et al.. Metoprolol or Verapamil in the Management of Patients With Hypertrophic Cardiomyopathy: A Systematic Review. Cureus. 2023
Zou Z, Xu FY, Wang L et al.. Antihypertensive and renoprotective effects of trandolapril/verapamil combination: a meta-analysis of randomized controlled trials. Journal of human hypertension. 2011
Bjerregaard L, Dybro AM, Saaby L et al.. Beta-Blocker (Bisoprolol) vs Calcium-Channel Blocker (Verapamil) in Nonobstructive Hypertrophic Cardiomyopathy: A Randomized Triple-Crossover Physiologic Trial. Journal of the American College of Cardiology. 2026
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