Anleptic

Indications

Carbamazepine is used to:

• prevent and control many types of epilepsy (fits or seizures), especially focal seizures and generalised tonic-clonic seizures;
• relieve the sharp facial nerve pain of trigeminal neuralgia;
• help prevent mood swings in bipolar disorder when other treatments are not suitable, under a specialist.

It is not used for absence seizures or myoclonic seizures, which it can make worse.

How It Works

Carbamazepine is an anticonvulsant (anti-seizure medicine). It calms overactive nerve cells in the brain by blocking sodium channels, which reduces the spread of the abnormal electrical signals that cause seizures and nerve pain.

Dosage and Administration

The dose is started low and raised slowly to reduce side effects. Your doctor will set the dose for you.

• Epilepsy, adults: often started at 100 to 200 mg once or twice a day, then increased step by step. The usual maintenance dose is 400 to 1200 mg a day, divided into 2 or 3 doses, as prescribed.
• Trigeminal neuralgia, adults: often started at 100 mg once or twice a day and increased until the pain is controlled, as prescribed.
• Bipolar disorder: as prescribed by a psychiatrist.
• Children: by age and weight, as prescribed.

Take with or after food. Swallow modified-release (long-acting) tablets whole or halved as directed; do not crush or chew them. Older people may need lower doses.

Do not stop suddenly, as seizures can return or get worse. If a dose is missed, take it when you remember unless the next dose is near; do not take two doses together.

Interactions

Carbamazepine interacts with many medicines. It speeds up the breakdown of others and can make them less effective, including hormonal contraceptives (pills, implants), Warfarin, some other epilepsy medicines, some antidepressants, some HIV medicines and some heart medicines. Other medicines can raise carbamazepine to harmful levels, such as Erythromycin, Clarithromycin, Fluconazole, Isoniazid, Verapamil and Diltiazem. It must not be taken with or within 14 days of an MAO inhibitor antidepressant. Grapefruit juice and alcohol should be avoided. Always tell your doctor and pharmacist that you take carbamazepine.

Contraindications

• Allergy to Carbamazepine or to tricyclic antidepressants
• Certain heart rhythm problems (atrioventricular block)
• A history of bone marrow problems (very low blood cell counts)
• Acute porphyria (a rare inherited blood disorder)
• Use of an MAO inhibitor within the last 14 days

Side Effects

Common, especially at the start: dizziness, drowsiness, unsteadiness, double or blurred vision, headache, nausea, vomiting, dry mouth and mild skin rash. It can also lower blood sodium, which may cause confusion, headache or more seizures.

Serious skin reactions can happen, mostly in the first months. The risk is higher in people who carry the HLA-B*1502 gene, which is common in South and Southeast Asian people, so your doctor may advise a blood test before starting.

Get medical help at once for: a spreading rash, blisters, peeling skin or mouth sores; fever, sore throat or mouth ulcers that do not go away; unusual bruising or bleeding; yellow skin or eyes; swelling of the face or trouble breathing; seizures that become more frequent; severe confusion; or thoughts of harming yourself.

Pregnancy and Lactation

Carbamazepine can increase the risk of birth defects, such as spina bifida. Do not stop it on your own if you become pregnant, because uncontrolled seizures are also dangerous; talk to your doctor quickly. Women who could become pregnant should plan pregnancy with their doctor, take folic acid as advised, and note that carbamazepine can make hormonal contraceptives fail. It passes into breast milk in small amounts. Many mothers can breastfeed, but watch the baby for unusual sleepiness, poor feeding or rash and tell the doctor.

Precautions and Warnings

• Regular blood tests may be needed (blood count, liver function and sodium).
• Take extra care with liver, kidney or heart disease, glaucoma, or problems passing urine.
• It can cause drowsiness and dizziness; do not drive or use machines until you know how it affects you.
• Avoid alcohol.
• Do not switch between different makes or forms without your doctor's advice.

Overdose

An overdose can cause severe drowsiness, unsteadiness, fits, heart rhythm problems, slow breathing and coma. It is a medical emergency; go to hospital immediately.

Therapeutic Class

Anticonvulsant (anti-seizure medicine); also used as a mood stabiliser.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.