Like all medicines, diltiazem can cause side effects, although not everyone gets them.
Common side effects
These common side effects of diltiazem happen in more than 1 in 100 people. They are usually mild and will not last long. There are things you can do to help cope with them:
Swollen hands, ankles or feet
Raise your legs or the swollen area on a chair or pillows when you can.
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 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 light-headed
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. Do not drink alcohol as it will make you feel worse.
Feeling tired, weak and generally unwell
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, cycle 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 where you use the cream or ointment
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're 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
Get more fibre into your diet 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.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
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 or call 111 now if:
- you get severe pain in your stomach
- the whites of your eyes turn yellow, or your skin turns yellow although this may be less obvious on brown or black skin – this can be a sign of liver problems
- your heartbeat becomes noticeable (palpitations)
Immediate action required: Call 999 or go to A&E now if:
- you get chest pain that does not stop after a few minutes or is new or worse if you already have angina
Chest pain is a possible sign of a heart attack and needs to be checked out as soon as possible.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to diltiazem.
Immediate action required: Call 999 now if:
- your lips, mouth, throat or tongue suddenly become swollen
- you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
- your throat feels tight or you're struggling to swallow
- your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
- you suddenly become very confused, drowsy or dizzy
- someone faints and cannot be woken up
- a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)
You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.
These can be signs of a serious allergic reaction and may need immediate treatment in hospital.
Other side effects
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 effect using the Yellow Card safety scheme.