verapamil
Brand: Calan, Isoptin, Verelan
Prototype: diltiazem
Drug Class: calcium channel blocker
Drug Family: antihypertensive
Subclass: non-dihydropyridine CCB (phenylalkylamine)
Organ Systems: cardiovascular
Mechanism of Action
Non-dihydropyridine CCB with greatest cardiac selectivity; negative chronotrope, dromotrope, and inotrope; also inhibits P-glycoprotein.
L-type calcium channel (predominantly cardiac)AV node conductionP-glycoprotein inhibitor
Indications
- angina
- hypertension
- AF rate control
- PSVT (IV)
- HOCM
- cluster headache prophylaxis
- bipolar disorder (adjunct)
Contraindications
- acute MI with pulmonary congestion
- cardiogenic shock
- 2nd/3rd degree AV block
- sick sinus syndrome
- WPW with AF
- concomitant beta-blocker (IV)
- HFrEF with systolic dysfunction
Adverse Effects
Common
- constipation (most common oral AE)
- bradycardia
- AV block
- hypotension
- edema
Serious
- heart block
- asystole (IV with beta-blockers)
- cardiogenic shock
- worsening HF
Pharmacokinetics (ADME)
| Absorption | 22% oral bioavailability (extensive first-pass) |
| Distribution | large Vd; crosses placenta |
| Metabolism | extensive hepatic CYP3A4 |
| Excretion | renal 70% |
| Half-life | 6-12 hours |
| Onset | 1-2 hours oral; 1-5 min IV |
| Peak | 1-2 hours |
| Duration | 6-8 hours IR; 24 hours SR |
| Protein Binding | 90% |
| Vd | 5 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| beta-blockers IV | severe bradycardia/asystole | major |
| digoxin | increases digoxin concentration (P-gp inhibition + renal clearance reduction) | major |
| simvastatin | CYP3A4 inhibition — increased statin myopathy risk | major |
| colchicine | P-gp inhibition increases colchicine exposure | major |
Nursing Considerations
- NEVER give IV verapamil + IV beta-blocker (fatal asystole)
- Most constipating CCB — docusate prophylaxis
- Monitor digoxin levels — verapamil raises digoxin significantly
- P-gp inhibitor affects many drug levels (colchicine, digoxin)
- Avoid in HFrEF — negative inotrope worsens systolic dysfunction
Clinical Pearls
- Most cardiac-selective CCB — greatest negative inotropic effect
- Constipation is most common oral adverse effect due to gut smooth muscle CCB effect
- P-gp inhibitor — numerous drug interactions beyond CYP3A4
- Contraindicated in WPW + AF (blocks AV node, forces conduction via accessory pathway)
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.