Diltiazem
2 medicines
Diltiazem is a calcium-channel blocker for high blood pressure, angina and atrial fibrillation, but it can cause dangerously slow heart rate or heart block, especially with a beta-blocker or existing conduction disease.
Key facts
- Diltiazem is a calcium-channel blocker that relaxes blood vessels and slows electrical conduction in the heart. It is sold as immediate-release tablets and once-daily extended-release capsules under names such as Cardizem and Tiazac.
- Extended-release capsules are taken once daily, usually at the same time; do not crush or split them, since this can release the full dose at once.
- Diltiazem slows the heart's electrical signals through the AV node. Combined with a beta-blocker, digoxin, or in anyone with an existing conduction problem, this can cause a dangerously slow heart rate or heart block.
- Seek urgent care for a pulse under 50 beats per minute, fainting, or severe swelling.
What diltiazem treats
Diltiazem treats high blood pressure and angina, chest pain caused by reduced blood flow to the heart muscle. It is also used to control the fast heart rate of atrial fibrillation and atrial flutter. It does not treat heart failure and is avoided when the heart's pumping function is already significantly weakened.
How diltiazem works
Calcium entering muscle cells makes them contract. Diltiazem blocks calcium channels in the smooth muscle of blood vessel walls and in the heart's conduction tissue. This relaxes the vessels, lowering blood pressure and easing the heart's workload, and it slows the electrical signal passing through the AV node, which controls how fast the heart's upper chambers can drive the lower chambers.
Before you take it
- Do not take diltiazem if you have sick sinus syndrome or second- or third-degree AV block without a pacemaker, severe low blood pressure, or acute heart failure with fluid in the lungs.
- Tell your prescriber about any beta-blocker, digoxin, or other heart-rhythm medicine you take; combining these with diltiazem raises the risk of severe bradycardia or heart block.
- Diltiazem raises blood levels of several other drugs, including some statins and immunosuppressants, by slowing how the liver clears them; your prescriber may need to adjust other doses.
- Grapefruit juice can increase diltiazem levels in some people.
Side effects
Common effects include swelling in the ankles, flushing, headache, and mild constipation.
Stop and seek urgent medical care for any of these:
- A pulse below 50 beats per minute, severe dizziness, or fainting.
- Worsening shortness of breath or swelling, which can signal heart failure.
- Chest pain that is new or worse.
- Signs of a severe allergic reaction, such as facial swelling or difficulty breathing.
Safety essentials
- Diltiazem can slow the heart rate to a dangerous degree, especially with existing conduction disease or when combined with a beta-blocker or digoxin; regular pulse and blood pressure checks catch this early.
- Never stop diltiazem abruptly if you take it for angina, since this can trigger a rebound increase in chest pain.
- Tell every prescriber and pharmacist you see diltiazem, since it interacts with many common drugs by slowing their breakdown in the liver.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.