Like all medicines, carbamazepine can cause side effects, although not everyone gets them.
Common side effects
These common side effects of carbamazepine may happen in more than 1 in 100 people. They're usually mild and go away by themselves. If they do not go away there are things you can do to help cope with them:
Feeling sleepy, dizzy or tired
Do not drive, cycle or use tools or machinery if you're feeling sleepy, tired or dizzy. Do not drink alcohol as this will make you feel more tired. If you feel dizzy, stop what you are doing and sit or lie down until you feel better.
As your body gets used to carbamazepine, these side effects should wear off. If they do not go after a few weeks, speak to your doctor.
Feeling or being sick (nausea or vomiting)
Stick to simple meals and do not eat rich or spicy food. It might help to take your carbamazepine after you've had a meal or snack.
If you're being sick, try having small, frequent sips of water or squash to avoid dehydration. Do not take any other medicines to treat vomiting without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet to find out what to do.
Headaches
Make sure you rest and drink plenty of fluids. Try not to drink too much alcohol. Ask your pharmacist to recommend a painkiller.
Talk to your doctor if headaches last longer than a week or are severe.
Dry mouth
Try chewing sugar-free gum or sucking sugar-free sweets.
Putting on weight
Try to eat a healthy balanced diet without increasing your portion sizes. Do not snack on foods that contain a lot of calories, such as crisps, cakes, biscuits and sweets. If you feel hungry between meals, eat fruit and vegetables and low-calorie foods. Increasing you level of exercise will also help to keep your weight stable.
Keep taking the medicine but talk to your pharmacist or doctor if these side effects bother you or do not go away.
Serious side effects
Skin rashes
It's common to get a skin rash with carbamazepine. Most skin rashes are not serious.
Stevens-Johnson syndrome is a rare side effect of carbamazepine. It causes flu-like symptoms, followed by a red or purple rash that spreads and forms blisters. The affected skin eventually dies and peels off.
It's more likely to happen in the first 8 weeks of starting carbamazepine, or when the dose is increased too quickly. It can also happen if carbamazepine is stopped suddenly for a few days and then restarted at the same dose as before, without reducing the dose and then increasing it slowly again.
Stevens-Johnson syndrome is more common in:
- children
- people who developed a rash with a different epilepsy medicine in the past
- people who are allergic to an antibiotic called trimethoprim
- people also taking a medicine called sodium valproate
To help prevent the chance of you getting a rash that could be confused with Stevens-Johnson syndrome, it's best not to try new medicines or food during the first 3 months of treatment with carbamazepine.
It's also best to not start carbamazepine within 2 weeks of a viral infection, vaccination, or rash caused by something else.
Immediate action required: Go to A&E now if:
- you get a severe rash with flushing, blisters or ulcers – these can be signs of Stevens-Johnson syndrome
Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.
Bring all the medicines you take with you.
Other serious side effects
It's unusual to have serious side effects after taking carbamazepine.
Call a doctor or call 111 straight away if:
- you have unusual bleeding or bruising, mouth sores, infections, a high temperature or sore throat – these can be signs of a blood disorder
- the whites of eyes turn yellow, or your skin turns yellow although this can be less noticeable on brown or black skin – these can be signs of a liver problem
- you have pain in your joints and muscles, a rash across the bridge of your nose and cheeks, and problems breathing – these are signs of lupus (systemic lupus erythematosus)
Immediate action required: Call 999 or go to A&E now if:
- you have thoughts of harming or killing yourself – a small number of people taking carbamazepine have had suicidal thoughts
Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.
Bring all the medicines you take with you.
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to carbamazepine.
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.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Long-term side effects
Some side effects of carbamazepine can happen over a long time. These include osteoporosis and osteopenia (increasing your risk of breaking a bone).
Your doctor can arrange for tests to check the strength of your bones. Regular exercise and a good diet can also help to keep your bones strong.
Other side effects
These are not all the side effects of carbamazepine. For a full list, check the leaflet inside your medicines packet.
Reporting side effects
You can report any suspected side effect using the Yellow Card safety scheme.
Visit the Yellow Card website for more information about reporting side effects.