Carbamazepine (Tegretol): Side Effects to Discuss With Your Prescriber

Carbamazepine, commonly prescribed as Tegretol (amongst other brand names), is a long-established anti-seizure medication (ASM). It is effective for many people, but it interacts with a number of other medicines and has a few serious reactions worth understanding. This guide provides general information and is not a substitute for advice from a prescriber, pharmacist or epilepsy specialist.

What carbamazepine is used for

Carbamazepine is used mainly for focal seizures and for some generalised seizures. It is also prescribed for trigeminal neuralgia (a nerve pain in the face) and in bipolar disorder. It is not suitable for every seizure type, as it can make certain generalised seizures worse — one reason the choice of ASM is always made by a specialist.

How carbamazepine works

Carbamazepine stabilises the electrical activity of nerve cells in the brain, reducing the excessive signalling that can lead to a seizure.

Common side effects

These are often more noticeable when treatment begins or the dose is increased, and frequently settle:

• Drowsiness, dizziness or unsteadiness
• Feeling or being sick
• Headache
• Dry mouth
• Weight gain
• Blurred or double vision

Taking the medication with food and avoiding alcohol can help with some of these. Persistent effects should be raised with the prescriber.

Serious side effects to act on

Serious skin reactions

Carbamazepine can, rarely, cause severe skin reactions such as Stevens-Johnson syndrome, which typically starts with flu-like symptoms followed by a spreading red or purple rash that blisters. Any severe or blistering rash needs urgent medical attention.

The risk of these reactions is higher in people who carry a particular genetic marker, HLA-B*1502, which is more common in people of Han Chinese, Thai and some other south and south-east Asian family backgrounds. A blood test to check for this marker is recommended before starting carbamazepine for people in these groups. This is a routine precaution, not a cause for alarm.

Please note: The rash can occur even for users that are well established on the medication.

Blood, liver and sodium

Seek prompt advice for:

• Blood problems — unusual bruising or bleeding, mouth ulcers, repeated infections, a sore throat or fever.
• Liver problems — yellowing of the skin or eyes.
• Low sodium (hyponatraemia) — headache, confusion, drowsiness or muscle cramps, which are more common in older adults.

Because of these possibilities, prescribers may arrange blood tests from time to time to monitor treatment.

Interactions and contraception

Carbamazepine speeds up the way the body processes many other medicines, which can make them less effective. Importantly, it reduces the effectiveness of hormonal contraception, including the pill, patch and implant. Anyone using hormonal contraception should discuss a reliable alternative or additional method with their prescriber. It can also affect the levels of other ASMs, which is why changes are always managed by a specialist.

Pregnancy

Carbamazepine in pregnancy is associated with an increased risk of birth defects, including neural tube defects such as spina bifida. Anyone taking it who is planning a pregnancy should seek a specialist review beforehand, and should not stop the medication without advice.

Do not stop suddenly

Stopping carbamazepine abruptly can trigger seizures. Any change should be planned with the prescribing team.

A note for carers and support staff

Those supporting someone on carbamazepine should be aware of the early skin-reaction warning signs, the signs of blood or sodium problems, and the fact that it can interact with other medicines — so any new medication should prompt a check with the pharmacist or prescriber. This sits alongside the person’s individual support plan.

This article is general education and does not replace advice from a prescriber or epilepsy specialist. Never change or stop an ASM without medical advice.