Diltiazem: uses, brands, side effects and cautions

Diltiazem is prescribed to treat high blood pressure, which helps prevent coronary heart disease, heart attacks and strokes; to prevent angina chest pain; and to reduce how often Raynaud attacks happen. Used as a cream or ointment it helps anal fissures to heal. It works by lowering blood pressure and making it easier for the heart to pump blood around the body. It is available on prescription only.

Brands the NHS names are Adizem, Angitil, Tildiem, Viazem and Zemtard. Tablets and capsules are used for blood pressure, angina and Raynaud; creams and ointments are for fissures.

Most adults and children aged 12 and over can take diltiazem. Tell your prescriber if you have had an allergic reaction to it, are pregnant, trying for a baby or breastfeeding, have liver or kidney disease, heart failure or heartbeat problems, a condition that slows the passage of food through the body, or the rare inherited condition porphyria.

Swallow tablets or capsules whole, usually with a glass of water; do not chew or crush them. They can be taken with or without food, at any time of day, but at around the same time or times each day. How many times a day depends on the product you have been given. Doses vary by condition and formulation, and the NHS page gives no figures, so follow your label.

The NHS says it is important to keep taking the same brand once you have started, since slow-release forms are not interchangeable. Long-term use is usual for blood pressure and angina and can continue for life; an anal fissure course usually takes around 6 to 8 weeks.

If you miss a dose and there are less than 4 hours (twice-daily dosing) or 12 hours (once daily) until the next, skip it. Never take an extra dose to make up. If you take more than prescribed, call NHS 111; symptoms may include feeling faint, dizzy or sleepy. Talk to your doctor before stopping, as it may cause blood pressure to rise.

Swollen hands, ankles or feet are common; raise your legs on a chair or pillows when you can. Headaches usually settle within a week, and paracetamol is safe to take. If you feel dizzy, sit or lie down until it passes. Flushing may ease if you cut down on coffee, tea and alcohol and keep cool. Eat smaller, slower meals for stomach pain or indigestion, and increase fibre and water for constipation. Skin irritation from the cream or ointment can be soothed with cool compresses.

Stop and call NHS 111 or a doctor for severe stomach pain, yellow eyes or skin, or heart palpitations. Call 999 for chest pain that does not stop after a few minutes, or for signs of a serious allergic reaction. Do not drive if dizzy or drowsy, and avoid alcohol as it will make you feel worse.

Named interacting medicines are the antibiotics clarithromycin, erythromycin and rifampicin, the antifungals itraconazole and ketoconazole, HIV and hepatitis C medicines, the epilepsy medicines carbamazepine and phenytoin, the immune suppressants ciclosporin and tacrolimus, and simvastatin at more than 20 mg a day.

The NHS says paracetamol is the best painkiller to take with diltiazem, and that if it does not work you can try ibuprofen. St John's wort is thought to affect how diltiazem works. The NHS diltiazem page does not mention grapefruit.

Diltiazem can be used during pregnancy but is not typically recommended; those taking it for high blood pressure may be switched. For angina or heart rhythm problems, an obstetrician and cardiologist should review the case and you should keep taking it until then. If your baby is healthy you can take it while breastfeeding, as only tiny amounts reach the milk. The NHS says diltiazem may affect male fertility, with no evidence of an effect on female fertility. Report suspected side effects via the Yellow Card scheme.