Carbamazepine: uses, side effects and cautions

Carbamazepine belongs to the group of medicines usually called anti-seizure or anticonvulsant drugs, although it has been used well beyond epilepsy. The NHS lists three licensed uses: seizures caused by epilepsy, trigeminal neuralgia (a sudden, severe, stabbing pain on one side of the face), and bipolar disorder in people for whom other medicines have not worked.

It is a prescription-only medicine in the UK. The NHS names Tegretol as the brand, and it is supplied as ordinary tablets, chewable tablets, a liquid and suppositories, so the form can be matched to the person, for example when swallowing tablets is difficult.

The NHS describes carbamazepine as working by changing the way nerves send messages to the brain, and it also acts on certain hormones that affect mood. In epilepsy the aim is to calm the abnormal bursts of electrical activity that produce seizures. In trigeminal neuralgia the same calming effect on nerve signalling is what eases the facial pain.

The NHS page does not give a time to full effect. It does say that most side effects should ease after a couple of weeks as the body gets used to the medicine, which is one reason doses are usually raised in steps rather than all at once.

Before prescribing, the clinician will ask about earlier reactions and existing conditions. The NHS lists a previous allergic reaction to carbamazepine or similar medicines, liver or kidney disease, glaucoma and schizophrenia as things to mention, together with pregnancy or plans for pregnancy.

• Tell the prescriber about every other medicine you use, including herbal products and vitamins, because carbamazepine interacts with many of them.

• Anyone who has had a rash or allergy to an anti-seizure drug in the past should say so before a new one is chosen.

• Women who could become pregnant need a conversation about contraception and folic acid before treatment is settled.

The NHS does not state a standard dose, because how much is needed depends on the condition, the age of the person and the type of medicine. Treatment typically starts low and goes up gradually, and the label on your own supply reflects your prescriber's instructions.

Ordinary tablets are swallowed whole with water, while chewable tablets may be chewed or swallowed whole. With the liquid, shake the bottle and use the syringe or spoon provided rather than a kitchen spoon. If a dose is missed, the NHS advice is to take it when you remember unless the next one is nearly due, in which case skip it; never take two doses together.

The commonly listed effects are dizziness, tiredness, dry mouth, changes in coordination, balance or speech, and feeling or being sick. Most settle within a couple of weeks. While you feel drowsy, dizzy or unsteady, the NHS says not to drive, ride a bike or use machinery.

Serious reactions are uncommon but need prompt action. The NHS highlights anaphylaxis, Stevens-Johnson syndrome (an itchy or painful rash with mouth ulcers and breathing difficulty), yellowing of the skin or eyes, and swollen ankles, feet or lower legs. The NHS advises calling 999 for suspected anaphylaxis or Stevens-Johnson syndrome and NHS 111 for the other serious effects.

Suspected side effects can be reported through the Yellow Card scheme, which anyone can use.

The NHS names several groups of medicines that interact with carbamazepine: some forms of hormonal contraception (pill, patch or implant), HRT, aripiprazole and similar mental health medicines, warfarin and similar blood thinners, and ciprofloxacin and related antibiotics. The effect can run in either direction, so a pharmacist check is worthwhile whenever anything new is added.

Grapefruit and grapefruit juice should be avoided because they can increase the chance of side effects. The NHS also says it is best not to drink alcohol, since it may affect you more than usual.

The NHS treats carbamazepine as higher risk in pregnancy. Anyone who may become pregnant is told to use reliable contraception, to tell their doctor if they are planning a pregnancy, and may be advised to take folic acid. Treatment is not simply stopped on the quiet, because uncontrolled seizures carry their own risks, so the decision is made with the specialist.

Breastfeeding is possible after discussion. The drug passes into breast milk, so the NHS suggests watching a breastfed baby for drowsiness, yellowing of the skin and eyes, and changes in stools. Because treatment is long term, regular reviews with the prescriber are the norm, particularly about contraception and pregnancy planning.

The NHS is direct on stopping: do not stop taking carbamazepine without talking to a doctor first, because stopping suddenly may cause seizures to return. If an overdose is suspected, speak to a pharmacist at once or use NHS 111, and go to A&E if told to, without driving yourself.

Other anti-seizure medicines exist, and specialists choose between them according to seizure type, other health conditions and pregnancy plans; the epilepsy medication choices guide on this site gives the wider picture. For trigeminal neuralgia and bipolar disorder the options differ again, and only the treating clinician can advise on a switch.