BMA Concise Guide to Medicine & Drugs


Brand names Adizem-SR, Calcicard-CR, Dilzem SR, Dilzem XL, Slozem, Tildiem, and others

Used in the following combined preparations None


Drug group Calcium channel blocker and antihypertensive drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Diltiazem belongs to the group of drugs known as calcium channel blockers. These drugs interfere with the conduction of signals in the muscles of the heart and blood vessels.

Diltiazem is used in the treatment of angina and longer acting formulations are used to treat high blood pressure. When this drug is taken regularly, it reduces the frequency of angina attacks but does not work quickly enough to reduce the pain of an angina attack that is already in progress.

Diltiazem does not adversely affect breathing and is valuable for people who suffer from asthma, for whom other anti-angina drugs may not be suitable.

Different brands of sustained-release (SR) diltiazem may not be equivalent, so you should always take the same brand.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, SR tablets, capsules, SR capsules.

Frequency and timing of doses 3 x daily (tablets/capsules); 1–2 x daily (SR tablets/SR capsules).

Adult dosage range 180–480mg daily.

Onset of effect 2–3 hours.

Duration of action 6–8 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Do not stop taking the drug without consulting your doctor; symptoms may recur. Stopping suddenly may worsen angina.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause dizziness or collapse. Notify your doctor urgently.


Diltiazem can cause various minor side effects that are also common to other calcium channel blockers. These include headache, nausea, vomiting, dry mouth, and ankle swelling. If any of these symptoms are severe, discuss with your doctor. More rarely, the drug may cause breast and/or gum enlargement, a rash, and, more seriously, a slowed heartbeat, which may cause dizziness or tiredness. If you develop any of these symptoms, contact your doctor. It is sometimes possible to control the adverse effects by adjusting the dosage.


Antihypertensive drugs Diltiazem increases the effects of these drugs, leading to a further reduction in blood pressure.

Anticonvulsant drugs Levels of these drugs may be altered by diltiazem.

Anti-arrhythmic drugs There is a risk of side effects on the heart if these are taken with diltiazem.

Beta blockers increase the risk of the heartslowing.

Digoxin Blood levels and adverse effects of this drug may be increased if it is taken with diltiazem. The dosage of digoxin may need to be reduced.

Simvastatin Diltiazem may increase blood levels and adverse effects of this drug. The dosage of simvastatin may need to be reduced.

Theophylline/aminophylline Diltiazem may increase the levels of this drug.


Be sure to tell your doctor if:

· You have long-term liver or kidney problems.

· You have heart failure.

· You are taking other medicines.

Pregnancy Not usually prescribed. Discuss with your doctor.

Breast-feeding The drug passes into the breast milk and may affect the baby. Discuss with your doctor.

Infants and children Not recommended.

Over 60 Increased likelihood of adverse effects. Reduced dose may therefore be necessary.

Driving and hazardous work Avoid such activities until you have learned how diltiazem affects you because the drug can cause dizziness due to lowered blood pressure.

Alcohol Avoid excessive amounts. Alcohol may lower blood pressure, causing dizziness.


No problems expected.