Verapamil
Calcium channel blocker (non-dihydropyridine), Antianginal, Antiarrhythmic (class IV), Antihypertensive
Verapamil
Calan, Calan SR, Verelan, Verelan PM, Isoptin SR
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Summary
Classes
Common uses
Hypertension0, Stable and vasospastic angina0, Atrial fibrillation/flutter rate control0, Paroxysmal SVT (acute IV)0, Cluster headache prophylaxis (high-dose, off-label)0
Pharmacy
Starting dose
IR 80-120 mg PO TID; ER 180-240 mg PO daily; IV 2.5-5 mg over 2 min for SVT termination (under monitoring); cluster prophylaxis up to 480-960 mg/d in divided doses
Preparations
IR 40, 80, 120 mg tablets; SR/ER 100-360 mg; IV 2.5 mg/mL
US FDA Max
~480 mg/d (oral) for cardiovascular indications; higher off-label for cluster
Pharmacology
Routes
Oral (IR and multiple ER), IV
Onset
IV: 1-3 minutes (SVT termination); PO IR: 30-60 minutes; ER: hours
Duration
IR: 6-8 hours; ER: 24 hours
Half-life
3-7 hours (IR); functional 24 hours (ER)[1]
Bioavailability
~20-35% (oral; extensive first-pass via CYP3A4 with R/S enantiomer differences)[1]
Pregnancy
Limited data; alternative antihypertensives generally preferred. Crosses placenta.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Verapamil is a phenylalkylamine non-dihydropyridine calcium channel blocker with the most pronounced AV nodal and cardiac myocyte L-type channel blockade in the class; it slows AV conduction, suppresses SVT, and reduces myocardial contractility, with modest peripheral vasodilation.0 Avoid in HFrEF (negative inotropy) and Wolff-Parkinson-White with AF (can accelerate antegrade accessory-pathway conduction). CYP3A4 substrate AND strong inhibitor — clinically dangerous interactions with simvastatin (max 10 mg), tacrolimus, cyclosporine, and many other CYP3A4 substrates[1]. Constipation is the dose-limiting non-cardiac adverse effect.
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Calan (verapamil HCl), Pfizer/Pharmacia, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/018817s033lbl.pdf