Calcium channel blockerPrescription only
Diltiazem
Tablet, capsule or ointment
Quick Summary
Diltiazem relaxes blood vessels and slows the heart rate.
Angina
Atrial fibrillation
Anal fissure
Medical Uses
Angina: Prevention.
Atrial fibrillation: Rate control.
Anal fissure: As an ointment.
How it's taken
Take as prescribed. Keep taking it even if you feel well, and don't stop suddenly without talking to your doctor.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Ankle swelling
Sometimes.
Slow heartbeat
Dizziness.
Headache
Sometimes.
Interactions
Beta blockers
Can slow the heart too much.
Statins
Some statin levels rise.
Critical Warnings
Heart failure
Not suitable for some types.
Slow pulse
Seek advice for fainting.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Diltiazem: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine
- Diltiazem: a medicine to treat high blood pressure(opens in a new tab) · NHS