Diltiazem is a medicine used to treat high blood pressure.

If you have high blood pressure, taking diltiazem helps to prevent future heart disease, heart attacks and strokes.

Diltiazem is also used to prevent chest pain caused by angina as well as Raynaud's phenomenon. It can also be used to help heal an anal fissure.

It's available on prescription only and comes as tablets, capsules, cream or ointment.

• Diltiazem works by lowering your blood pressure and makes it easier for your heart to pump blood around your body.
• You can take diltiazem at any time of day. Try to make sure it's around the same time or times every day.
• Common side effects include swollen hands, ankles or feet, headaches and constipation.
• Diltiazem starts to work on the day you start taking it, but for high blood pressure and angina it may take a couple of weeks to work fully.
• It's important to keep taking diltiazem even if you feel well, as you'll still be getting the benefits of the medicine.

Diltiazem can be taken by adults and children aged 12 years and over.

Diltiazem is not suitable for some people.

To make sure diltiazem is safe for you, tell your doctor if you:

• have had an allergic reaction to diltiazem or any other medicines in the past
• are trying to get pregnant, are already pregnant or you're breastfeeding
• have liver disease or kidney disease
• have heart failure or problems with your heart beat
• have a condition that causes food to move slower than usual through your body
• have porphyria (a blood disorder)

Take diltiazem exactly as your doctor has told you. If you're not sure, check with your doctor or pharmacist.

You can take diltiazem at any time of day but try to make sure it's around the same time or times every day.

Dosage

Your dose of diltiazem depends on why you need the medicine and what kind your doctor has prescribed. It is important to keep taking the same brand of diltiazem once you have started.

Diltiazem tablets or capsules come as standard (immediate release) or slow-release (prolonged release, SR or XL). Your doctor will tell you whether you need to take them once a day or in divided doses throughout the day.

Slow-release tablets release diltiazem slower than the immediate-release tablets.

How to take or apply it

You can take diltiazem with or without food. Swallow diltiazem tablets or capsules whole, usually with a glass of water. Do not chew or crush them.

If you find tablets or capsules difficult to swallow, speak to a pharmacist or doctor, as there may be other options.

With some of the capsules and tablets you might notice what looks like a whole capsule or tablet in your poo. Do not worry, this is normal. It's just the empty outer shell of the capsule or tablet which your body has not digested.

For anal fissure, you'll need to apply a 2cm length of diltiazem cream or ointment to the broken skin on your anus, twice a day, usually for 6 weeks. Follow the instructions on the packaging.

Will my dose go up or down?

If the dose you start on does not work well enough (your blood pressure does not lower enough, or your angina is not controlled), then your doctor will gradually increase your dose.

Your doctor may also lower your dose if the side effects bother you.

What if I forget to take it?

If you forget to take a dose and you usually take diltiazem:

• once a day – take it as soon as you remember, unless it's less than 12 hours until your next dose. In this case, leave out the missed dose and take your next dose at the usual time.
• twice a day – take it as soon as you remember, unless it's less than 4 hours until your next dose. In this case, leave out the missed dose and take your next dose at the usual time.
• three times a day – leave out that dose and take your next dose at the usual time.

Do not take a double dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask a pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Too much diltiazem can make you feel faint, dizzy or sleepy. This is because it can cause your heart to beat irregularly.

If you need to go to hospital, do not drive yourself; get someone else to drive you or call for an ambulance. Find your nearest A&E

Take the diltiazem packet or leaflet inside it, plus any remaining medicine, with you.

Like all medicines, diltiazem can cause side effects, although not everyone gets them.

Common side effects

These common side effects happen in more than 1 in 100 people. They are usually mild and will not last long.

Talk to a pharmacist or doctor if the side effects bother you or last for more than a few days:

• swollen hands, ankles or feet
• headaches
• feeling dizzy and lightheaded
• feeling tired, weak and generally unwell
• feeling hot (flushing) and redness of the skin
• itching or burning on the skin where you use the cream or ointment
• stomach pain, indigestion and constipation

Serious side effects

Serious side effects after taking diltiazem are rare and happen in less than 1 in 10,000 people.

Stop taking diltiazem and call a doctor straight away if you get:

• severe pain in your stomach
• yellow skin or the whites of your eyes turn yellow – this can be a sign of liver problems

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to diltiazem.

These are not all the side effects of diltiazem. For a full list, see the leaflet inside your medicine packet.

You can report any suspected side effects to the UK safety scheme.

What to do about:

• swollen hands, ankles or feet – raise your legs when you're sitting down. This will get better after a few days as your body gets used to the medicine. If it does not, or it gets worse, speak to your doctor.
• headaches – make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask a pharmacist to recommend a painkiller. Paracetamol is safe to take with diltiazem. Headaches should usually go away after the first week of taking diltiazem. Talk to your doctor if they last longer than a week or are severe.
• feeling dizzy and lightheaded – if diltiazem makes you feel dizzy, stop what you're doing and sit or lie down until you feel better. Do not drive, ride a bike or operate tools or machinery until you feel OK.
• feeling tired and weak – make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Try to take diltiazem at a time when you can sit down (or lie down) when the symptoms are at their worst. If you're still having problems after a week, speak to your doctor, as they may need to change you to a different type of medicine. Do not drive or use tools or machinery until you feel OK.
• feeling hot (flushing) and redness of the skin – try cutting down on coffee, tea and alcohol. It might help to keep the room cool and use a fan. You could also spray your face with cool water or sip cold or iced drinks. The flushing should go away after a few days. If it does not go away or it's causing you problems, contact your doctor.
• itching or burning on the skin – try holding something cool on your skin like a damp towel. Take cool baths or showers. If you have itchy skin, use an unperfumed moisturiser regularly. However, do not use moisturiser on an anal fissure as this will irritate it more. Keep your nails clean, short and smooth and try to pat or tap your skin rather than scratching.
• stomach pain – try to rest and relax. It can help to eat and drink slowly and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you are in a lot of pain, speak to a doctor or pharmacist. 
• indigestion – it might help to eat smaller and more frequent meals, and to eat and drink slowly. Talk to your doctor if the symptoms get worse.
• constipation – eat more high-fibre foods such as fresh fruit, vegetables and cereals, and drink plenty of water. Try to exercise regularly, for example, by going for a daily walk or run. If this does not help, talk to a pharmacist or doctor. Watch this short video about how to treat constipation.