Common questions about carbamazepine

Carbamazepine is an anti-convulsant (or anti-epileptic) medicine. It works by stabilising the electrical activity in the brain and nerves.

For epilepsy, carbamazepine works by stopping electrical signals from building up in the nerve cells in the brain. It also reduces the release of a chemical (neurotransmitter) called glutamate. Too much glutamate can cause seizures.

For nerve pain, carbamazepine works by stabilising the electric signals in your nerves. This stops the pain signals being sent to your brain.

We do not fully understand how carbamazepine works for treating bipolar disorder. However, it's thought to reduce the glutamate activity in the brain.

It can take 1 to 2 weeks for carbamazepine to work fully.

Many people take carbamazepine safely for many months or years.

However, there are some side effects that can happen over a long time. Long-term treatment with carbamazepine can cause 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.

There are many different medicines for treating epilepsy.

It's not possible to say that one works better than the other. It varies from person to person and depends on the type of seizures and how often you have them.

If you have epilepsy, the choice will depend on the type of seizures that you have. Your doctor will discuss the best medicine for you.

Other epilepsy medicines include:

• gabapentin
• lamotrigine
• levetiracetam
• phenytoin
• pregabalin
• sodium valproate
• topiramate
• valproic acid
• brivaracetam
• clobazam
• ethosuximide

To help to decide, your doctor will take into account your age and sex, the medicines you're already taking and any other health problems you have.

It's usual to try to treat epilepsy using a single medicine. If this medicine is not working well, or you're getting side effects, your doctor will generally try you on a different one.

If a single medicine is not preventing your seizures, then your doctor may recommend taking 2 or more epilepsy medicines at the same time.

If carbamazepine is giving you side effects, or you're worried it is not working for you, ask your doctor or specialist to recommend a different medicine.

Carbamazepine is usually the first medicine given to treat nerve pain or trigeminal neuralgia.

Medicines called phenytoin or gabapentin might be used if carbamazepine does not work or causes too many side effects.

Some other medicines may be used to treat nerve pain or trigeminal neuralgia. Your doctor or specialist will find the medicine that works best for you.

If you have bipolar disorder, there are several types of medicine to prevent low mood. It's not possible to say that one works better than another and it varies from person to person.

Lithium is commonly used for treating low mood in bipolar disorder, as well as a medicine called quetiapine (an antipsychotic medicine).

Your doctor or specialist will find the medicines that work best for you.

If you want to switch medicines, it's very important to follow your doctor's advice.

Switching from carbamazepine to a different medicine will be different for each person.

If you want to switch, you'll usually start taking the new one at a low dose and slowly build up the dose while you are still taking carbamazepine. If you have epilepsy this protects you from seizures until the new medicine starts to work.

Once you're taking the correct dose of the new medicine, you should be able to slowly reduce your dose of carbamazepine.

It can take several weeks or months until you've stopped taking carbamazepine completely.

If you take carbamazepine for epilepsy, you may have seizures once you stop taking it. You can prevent these withdrawal seizures by reducing the dose of your carbamazepine gradually.

If you are taking if for bipolar disorder or nerve pain, your condition could get worse for a short time after stopping it.

However, you're unlikely to get any withdrawal symptoms when you stop taking this medicine.

You can take carbamazepine as normal before and after surgery.

Carbamazepine may reduce the effects of some muscle relaxants so these may need to be increased.

Tell your doctor you are on carbamazepine if you need surgery.

Carbamazepine might stop these contraceptives from working:

• combined hormonal contraceptives (the combined pill, contraceptive patches, and vaginal ring) – look out for bleeding between periods, which might be a sign that the pill is not working. Talk to your doctor if this happens. Your doctor may advise you to use a different type of contraceptive, or condoms as well as combined hormonal contraception
• progestogen-only contraceptive pill or implants – your doctor may advise you to use a different type of contraceptive that is not affected by carbamazepine
• emergency contraception – tell your doctor or pharmacist that you take carbamazepine if you need emergency contraception – you may need an increased dose or to use a coil

You can use the contraceptive injection or coil with carbamazepine.

If carbamazepine makes you sick (vomit), your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.

Find out more:

• What to do if you're sick or have diarrhoea when taking the combined pill
• What to do if you're sick or have diarrhoea when taking the progestogen-only pill

If you have epilepsy, you're entitled to free prescriptions for all of your medicines, not just your epilepsy ones.

To claim your free prescriptions you'll need a medical exemption certificate.

The application form for the medical exemption certificate is called FP92A. You can get this from your doctor's surgery. You will need to fill in the form, then your doctor will sign it and send it off.

You may feel sleepy, tired or dizzy when you first start taking carbamazepine. This may also happen if your dose has increased. If you're affected, do not drive, ride a bike, or operate machinery until you feel better.

It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.

Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking carbamazepine. GOV.UK has more information on the law on drugs and driving.

If you have epilepsy, you're not allowed to drive until you've had no seizures for 1 year.

You are also not allowed to drive for 6 months after you change your epilepsy medicine.

Drinking alcohol while taking carbamazepine may make you feel sleepy or tired. It's best to stop drinking alcohol for the first few days, until you see how the medicine affects you.

Do not drink grapefruit juice if you're taking carbamazepine. It increases the concentration of carbamazepine in your body and increases the risk of side effects.