How it works
What does carbamazepine do?
Carbamazepine is a type of medicine called a ‘mood stabiliser’ as it controls feelings of excitability and over-activity. It can also help with periods of low mood.
Carbamazepine is usually only prescribed after you have already tried other mood stabilisers such as lithium, olanzapine and valproate.
Carbamazepine can help to calm down the brain. There are gateways in the brain called ‘sodium channels’, which can be open or closed. When they are open, there is more electrical activity in the brain. Carbamazepine locks on to closed sodium channels and keeps them closed. Reduced electrical activity leads to reduced release of chemical transmitters that excite the brain, which lowers the amount of glutamate, dopamine and noradrenaline circulating around the brain.
How long does carbamazepine take to start working?
It should only take a few days for carbamazepine to start helping.
Your doctor might start you on a low first dose, and then bring it up to your normal dose to reduce the chance of side effects.
The effect will build over the first one to two weeks. It will take a few weeks at your normal dose for carbamazepine to show its full effect.
How long will I need to take carbamazepine for?
Most people take carbamazepine for at least six months.
You and your doctor should talk about how long you need to take carbamazepine before you start your treatment.
You might have to change your dose to get the best effect for you.
If you only get ill every 12 months you will probably need to take it for longer than 12 months to get any benefit.
Your doctor needs to know if...
You need to talk to your doctor or pharmacist before you take carbamazepine if you think you may be allergic to carbamazepine (or similar medicines like oxcarbazepine (Trileptal™)), tricyclic antidepressants like amitriptyline, or an epilepsy medicine called phenytoin.
You also need to talk to your doctor or pharmacist before starting treatment with carbamazepine if any of the following apply to you:
- you have any heart or liver problems
- you have ever had problems with your bone marrow
- you have a blood problem called porphyria
- you are from a Han Chinese or Thai family background (certain reactions to this medicine are more likely in people of these origins – your doctor will want to check if you’re at risk of this problem by doing a blood test)
- you have taken drugs called monoamine oxidase inhibitors (MAOIs), used to treat depression, within the last 14 days - MAOI drugs include moclobemide, isocarboxazid, phenelzine and tranylcypromine
- you are pregnant or planning to become pregnant
- you are breastfeeding
- you have epilepsy where you get mixed types of seizures (fits) which include absences
- you have any eye problems such as glaucoma (increased pressure in the eye)
How can carbamazepine be taken?
You can take carbamazepine as a tablet or as a liquid medicine.
Carbamazepine tablets are available in 100mg, 200mg and 400mg strengths.
There are two different types of tablets for carbamazepine:
- slow release (SR), prolonged release or modified release. These must not be chewed, or they will not give you the long-lasting effect. You should swallow each tablet whole or break it in half along the line in the middle
- ordinary tablets that should be swallowed whole or broken in half along the line in the middle
You should only take carbamazepine as agreed with your doctor
You will get the best effect from this medicine if you take it regularly without missing doses.
Make sure that you know your dose. If it is not written on the label, check it with your pharmacist or doctor.
You may have to take it more than once a day.
You will probably start on a low dose and it will increase until it is right for you.
It doesn’t matter what time you take it each day – choose a time that you can always remember. This could be a mealtime, or when you brush your teeth.
You can take it before or after food.
Different brands of carbamazepine tablets can release slightly different amounts of carbamazepine, even if they are the same strength. Ask your pharmacist to always give you the same brand of tablets. Keep the box or blister pack to show them. This is more important if you are taking carbamazepine for seizures (fits).
What if I miss a dose?
If you forget to take a dose, take it as soon as possible unless it is less than four to six hours until your next dose.
If you forget to take it by the time of the next dose, just take the next dose.
Do not take a double dose.
What will happen if I forget to take my carbamazepine?
If you forget to take your tablets for a few days, you may start getting your old symptoms back. Talk to your doctor if this happens.
You may need to restart the carbamazepine slowly or find a different treatment.
Stopping the use of carbamazepine
Once you start taking carbamazepine, the brain adjusts to the new balance of chemicals.
If you stop taking the carbamazepine all at once, the balance starts to change again. You could get your old symptoms back.
There is a risk that you may get seizures (fits). This is because even if you are not taking the carbamazepine for epilepsy, your body has got used to having an anticonvulsant medication on board.
When you decide with your doctor to stop taking carbamazepine, you will probably reduce the dose slowly over at least a month to stop you getting any uncomfortable withdrawal symptoms.
Go and speak to your doctor if you have missed a few doses or have decided to stop taking your medication.
The information on this page was reviewed by the College of Mental Health Pharmacy in March 2020.