Side effects
Side effects that start when you begin taking carbamazepine should improve or go away after a few days or weeks. If they don’t, or they get worse, you should go back to your doctor.
Do not stop taking the tablets until you talk to your doctor, or you may get withdrawal symptoms as well.
Very common side effects of taking carbamazepine (affecting more than one in ten people) include:
- leucopoenia (a reduced number of the cells which fight infection making it easier to catch infections)
- dizziness and tiredness
- feeling unsteady or finding it difficult to control your movements
- feeling or being sick
- changes in liver enzyme levels (usually without any symptoms)
- skin reactions, which may be serious
Common side effects of taking carbamazepine (affecting up to one in ten people) include:
- changes in the blood making you more likely to bruise or bleed
- fluid retention and swelling
- weight increase
- low sodium in the blood which might result in confusion
- headache
- double or blurred vision
- dry mouth
- loss of appetite
There are other side effects that you can get when taking this medicine – we have only included the most common ones here. Please look at the leaflet inside your medicine box, or ask a doctor or pharmacist, if you want to know if you are getting a side effect from your medicine.
When taking this medication, you are also at risk of developing a rare side effect called Steven-Johnson Syndrome. Symptoms are flu-like at first (fever, headache and all-over body ache) then ulcers could appear in your mouth, throat, nose and sex organs. You could also get conjunctivitis (red eyes) and a rash that spreads all over your body. If you think you are getting these symptoms, stop taking the tablets immediately and see a doctor without delay.
Body
Carbamazepine can cause weight gain or weight loss.
It is hard to know how it will affect each person until you take it.
Talk to your doctor about this if it worries you.
Sex and fertility
Sex
Carbamazepine can have side effects that might affect your sex life. These include:
- swelling of the breasts and some milk flow (regardless of gender)
- not wanting to have sex as much as usual, or at all
- spotting and/or bleeding between periods
- difficulty getting an erection (getting hard)
These effects should pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what else you could try.
Fertility
There have been a few reports of lower sperm count and quality in people who are taking carbamazepine. Talk to your doctor about this if you are affected and trying to have a baby with your partner.
Carbamazepine can make hormone contraceptives like 'the Pill' and implants less effective – you might need to change your contraceptive to avoid the risk of pregnancy.
Condoms and other barrier methods (cap, diaphragm) will not be affected by carbamazepine so you can use those safely while taking it.
Pregnancy, post-natal and breastfeeding
Pregnancy
There have been reports of effects on the development of the baby from people who took carbamazepine during pregnancy. The risk is lower if your dose of carbamazepine is less than 1g (1000mg) per day.
If you become pregnant while taking carbamazepine, you should talk to your doctor about whether you should carry on taking it.
Your doctor should give you supplements like folic acid and vitamin K which are safe to take with carbamazepine.
Your dose of carbamazepine may need to increase later in pregnancy to keep the benefit.
Post-natal
Carbamazepine can cause some symptoms in some newborn babies like sleepiness, difficulty feeding, being sick and having diarrhoea (loose poo).
Your baby may need a vitamin K injection to help with healthy blood-clotting.
Some newborn babies have had seizures (fits) or breathing problems.
Your midwife can look out for this and give you help.
Breastfeeding
Some carbamazepine is passed to the baby in breast milk – you may breastfeed but look out for any side effects like heavy-sleeping or skin reactions.
Talk to your doctor or midwife about the risks and benefits of breastfeeding.
Extra checks may be made on your baby for any liver problems or skin rashes.
Driving and transport
Do not drive a car or ride a bike just after you start taking carbamazepine.
Taking carbamazepine may make you feel sleepy or dizzy, and may affect your eyesight, when you start taking it.
This could affect you if you drive a car, ride a bike, or do anything else that needs a lot of focus. It might be best to stop doing these things for the first few days, until you know how it affects you.
Do not worry - most people do these things as normal while taking carbamazepine.
School and exams
Try not to take carbamazepine for the first time just before your exams.
You may feel dizzy, restless or confused when you first take carbamazepine, and it could affect your eyesight.
You should talk to your doctor about any future exams if you are starting carbamazepine. You might decide together to delay starting it until you have done them.
If they are more than a week away, however, you might find that it is better to start carbamazepine to improve your motivation to study.
Do not worry - most people take exams as normal while taking carbamazepine.
Friends and family
You may want to let your family and friends know you are taking carbamazepine so they can support you and help you look out for side effects.
For guidance on this, check out our page on getting support with your medication.
Sport
Carbamazepine is not a banned substance in sport.
It could, however, affect your concentration and eyesight.
If you play sports that need a lot of focus, you might want to stop for a short while when you start taking carbamazepine, to see how it affects you.
Do not worry - most people play sports as normal while taking carbamazepine.
Alcohol and street drugs
Alcohol
You can continue to drink alcohol while taking carbamazepine but having the two together might make you very sleepy.
If you drink a lot of alcohol, however, it could increase the carbamazepine level in your body, and this could be dangerous.
So, during the first few days, it might be best to stop drinking alcohol until you see how the medicine affects you.
If you want to drink alcohol, remember that you might be sleepy and make sure you can get home safely.
Street drugs
Using both cannabis and carbamazepine at the same time might make you feel sleepier.
Cannabis and other drugs may have their own side effects on your mental health, like anxiety or psychosis. For more information, have a look at our drugs and alcohol page.
Carbamazepine reduces the level of methadone in the body when they are used together, so if you stop carbamazepine your methadone level might go up dangerously – talk to your doctor about this before you stop carbamazepine.
Carbamazepine drives cocaine breakdown to make norcocaine. This chemical is more dangerous to your heart and liver than cocaine itself.
Taking carbamazepine and alcohol together can affect your liver, so you may want to have regular liver function tests.
Prescription medicines
Many medicines, including some vitamins, do not mix well with carbamazepine and the dose of some medicines will need to be adjusted.
Talk to your doctor about any medications you are taking before you begin treatment with carbamazepine.
Talk to your pharmacist if you buy any medications over the counter to treat common illnesses like colds and flu or topical applications that you put on your skin.
Other interactions
Do not take carbamazepine tablets with grapefruit juice. Grapefruit juice may increase the absorption of carbamazepine from the gut and cause the levels of carbamazepine to increase.
Monitoring
When you start taking carbamazepine, the doctor should weigh you and do some blood tests to check your blood and liver function.
These weight and blood tests should be done again after every six months of taking carbamazepine.
A blood test might also be done every six months to check the levels of carbamazepine. If carbamazepine is helping improve your mood and you are not getting side effects, then levels are less important. Levels are more likely to be done if you are taking carbamazepine for seizures (fits) as there is a finer balance to be kept.
References and further reading
For more helpful links and information, have a look at our references and further reading page.