Diltiazem is a calcium channel blocker (non-dihydropyridine) used to treat high blood pressure, angina (chest pain), and certain heart rhythm problems (notably atrial fibrillation/flutter with rapid heart rate).
Key points
- How it works: It relaxes blood vessels (vasodilation) and slows the heart rate and AV node conduction. This lowers blood pressure and can reduce the heart’s workload; it also helps control rapid heart rates in some arrhythmias.
- Common uses
- Hypertension (high blood pressure)
- Chronic stable angina and vasospastic angina
- Atrial fibrillation or atrial flutter with rapid ventricular response (to slow the heart rate)
- Forms and dosing
- Immediate-release tablets (e.g., 30 mg, 60 mg, 90 mg, taken several times daily)
- Extended-release/long-acting capsules (e.g., 120 mg, 180 mg, 240 mg, 300 mg, 360 mg, 420 mg once daily)
- Intravenous form for acute settings (in hospital)
- Dosing depends on condition, formulation, and individual response. Do not adjust without a clinician’s guidance.
- Important side effects
- Common: dizziness, headache, flushing, swelling of ankles/feet (edema), nausea
- Briskly notable: bradycardia (slow heart rate), low blood pressure
- Less common: constipation (less with diltiazem than with some other calcium blockers), fatigue
- Serious: signs of very slow heart rate, fainting, severe shortness of breath, swelling of ankles/legs that rapidly worsens
- Contraindications and cautions
- Do not use with significant bradycardia, second- or third-degree AV block, sick sinus syndrome (unless there’s a pacemaker), or decompensated heart failure with reduced ejection fraction.
- Use with caution in heart failure with preserved ejection fraction, liver disease, or very low blood pressure.
- Can affect the heart’s rhythm; tell your doctor if you already have a slow heart rate or certain rhythm problems.
- Interactions to watch
- Additive effects with other heart-rate slowing drugs (beta-blockers, digoxin, certain antiarrhythmics) may cause too slow a heart rate or low blood pressure.
- Grapefruit juice (and some CYP3A4 inhibitors) can increase diltiazem levels; discuss diet and other meds with your clinician.
- Other blood pressure-lowering drugs can augment hypotension.
- Inform your prescriber about all medicines you take, including OTC drugs and supplements.
- Pregnancy and breastfeeding
- Diltiazem is generally categorized as not proven safe in pregnancy (category C/D in some labeling); use only if clearly needed and prescribed by a clinician. Discuss risks and alternatives with your provider. Breastfeeding safety is not well established; ask your doctor.
- Monitoring
- Regular checks of blood pressure and heart rate
- Periodic liver function tests and ECG if used long-term or in combination with other heart meds
- Watch for signs of low blood pressure or slowed heart rate
If you’d like, tell me your indication (hypertension, angina, or a rhythm problem), your current dose/form, and any other medications you take. I can tailor a more specific overview, including typical dosing ranges and key precautions. And as always, consult your clinician for personalized medical advice.