Diltiazem
Brand names: Cardizem, Tiazac
Class: 🩺 Calcium Channel Blockers
When a vignette puts you on a rate-control question and a beta-blocker is contraindicated, diltiazem is usually the answer. As a non-dihydropyridine calcium channel blocker, it slows AV node conduction — making it useful for atrial fibrillation/flutter rate control, paroxysmal SVT termination, hypertension, and stable or vasospastic angina. The board pitfall is combining diltiazem with a beta-blocker: additive bradycardia and AV block. It is also contraindicated in HFrEF and in pre-existing AV block without a pacemaker. Diltiazem is a CYP3A4 inhibitor — watch for interactions with simvastatin, lovastatin, and tacrolimus. Constipation is common; orthostasis and edema appear at higher doses.
✅ Indications
A-fib/a-flutter rate control, SVT, HTN, stable angina.
⚙️ Mechanism of Action
Non-dihydropyridine CCB — slows AV node.
📏 Dosing
IV: 0.25 mg/kg bolus + drip. PO: 120–360 mg daily (ER).
🚫 Contraindications
HFrEF (negative inotrope), 2nd/3rd degree AV block without pacemaker, sick sinus syndrome, WPW with a-fib.
⚠️ Adverse Effects
Bradycardia, AV block, constipation, peripheral edema, ↑ liver enzymes.
🔬 Monitoring
HR, BP, ECG for AV block.
💎 Board Pearls
- 🫀 First-line rate control in a-fib for patients WITHOUT CHF (HFrEF).
- 🚫 Avoid with beta-blockers — additive AV nodal blockade → severe bradycardia.
Related Drugs in This Class
- Amlodipine — Norvasc
- Nifedipine — Procardia, Adalat
- Verapamil — Calan, Verelan
Sources
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