Known brand names include Tegretol and Epitol.
An antiepileptic (anticonvulsant) taken by mouth as tablets, extended-release tablets, or a liquid suspension. It treats several seizure types and the facial nerve pain of trigeminal neuralgia. Its boxed warning covers severe skin reactions, linked to the inherited HLA-B*1502 gene variant, and rare but serious drops in blood cells.
Labeled use. Partial seizures with complex symptomatology, generalized tonic-clonic seizures, and mixed seizure patterns; not absence seizures.
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Carbamazepine is effective for focal seizures and is the classic first-line drug for trigeminal neuralgia. An extended-release capsule (Equetro, not covered here) is approved for acute mania in bipolar I disorder, so carbamazepine is also taught as a mood stabilizer. Many clinicians now prefer lamotrigine or levetiracetam for long-term epilepsy care because carbamazepine has many enzyme-induction interactions, HLA-B*1502 skin risk, hyponatremia, and teratogenic risk. It can worsen absence and myoclonic seizures.
Mechanism unknown. In animals it reduces polysynaptic responses and blocks post-tetanic potentiation, and it is chemically related to the tricyclic compounds. It is metabolized in the liver, mainly by CYP3A4, to carbamazepine-10,11-epoxide, which is also anticonvulsant in animals. It induces its own metabolism (autoinduction complete in 3 to 5 weeks), so half-life falls from 25 to 65 hours to 12 to 17 hours. It is a potent CYP3A4 inducer and also induces CYP1A2, 2B6, and 2C8/9/19. About 76% is protein bound.
Narrow therapeutic index. The label gives a usual adult therapeutic level of 4 to 12 mcg/mL and directs measuring plasma levels to see whether they are in the therapeutic range when response is unsatisfactory or interacting drugs are added or stopped.
Doses come from the FDA label. Study tool, not for clinical decisions.
No dose table. Use only after a careful benefit-to-risk appraisal in renal damage. Renal problems including oliguria, azotemia, and renal failure have been reported, so baseline and periodic urinalysis and BUN are recommended.
No dose table. It is metabolized in the liver; use only after a careful benefit-to-risk appraisal in hepatic damage. Check liver function at baseline and periodically, especially with a history of liver disease, and stop for new or worsening liver dysfunction or active liver disease.
Serious, sometimes fatal skin reactions (SJS and TEN), about 10 times more common in some Asian countries and strongly linked to HLA-B*1502. Screen patients with at-risk ancestry before starting, and do not treat allele-positive patients unless the benefit clearly outweighs the risk. Aplastic anemia and agranulocytosis occur 5 to 8 times more often than in the general population; get complete baseline blood counts, monitor closely if counts fall, and consider stopping for significant bone marrow depression.
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No specific antidote. Signs begin 1 to 3 hours after ingestion and are mainly neuromuscular: impaired consciousness up to coma, convulsions (especially in small children), twitching, tremor, ataxia, nystagmus, and dilated pupils, with irregular or depressed breathing, tachycardia, blood pressure changes, and conduction disorders. Remove the drug early (gastric lavage, activated charcoal), protect the airway, treat shock with fluids and vasopressors if needed, and treat seizures with diazepam or barbiturates while watching for worse respiratory depression. Monitor breathing, ECG, blood pressure, temperature, and kidney and bladder function for several days; dialysis is for severe poisoning with renal failure.
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Can cause fetal harm, including spina bifida, craniofacial and heart defects, and developmental delays. Combination antiepileptic therapy may raise the risk, so monotherapy may be preferable. Newborns have had seizures, respiratory depression, vomiting, diarrhea, or poor feeding, possibly withdrawal. Do not stop abruptly during pregnancy because of the risk of status epilepticus, and encourage enrollment in the NAAED Pregnancy Registry.
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Carbamazepine and its epoxide pass into breast milk, at about 0.4 and 0.5 times the maternal plasma level; a nursing infant may receive about 2 to 5 mg of drug daily. Because of possible serious infant reactions, decide whether to stop nursing or the drug.
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Under 6 years: 10 to 20 mg/kg/day in two or three doses (tablets) or four doses (suspension), increased weekly; response usually comes below 35 mg/kg/day, and safety above 35 mg/kg/24 hours is not established. Ages 6 to 12: 100 mg twice daily (200 mg/day), adding up to 100 mg/day weekly; usual maintenance 400 to 800 mg daily, maximum 1000 mg daily. The therapeutic range of 4 to 12 mcg/mL is the same as in adults. The suspension contains propylene glycol; children under 5 are at highest risk of toxicity, and neonates should receive it only when no alternative exists.