Question
Carbamazepine
Answer
Carbamazepine is a Na⁺ channel-blocking antiepileptic, structurally related to the tricyclic antidepressants.
MOA: carbamazepine → binds and stabilizes the inactivated state of voltage-gated Na⁺ channels → use-dependent block of sustained high-frequency neuronal firing.
Uses: focal (partial) seizures, generalized tonic-clonic seizures, trigeminal neuralgia (drug of choice), bipolar disorder (mood stabilizer).
Adverse effects: sedation, diplopia, ataxia, hepatic enzyme induction (reduces efficacy of oral contraceptives and other co-administered drugs), hyponatremia (SIADH-like effect), Stevens-Johnson syndrome/toxic epidermal necrolysis (HLA-B*1502 association, particularly relevant in patients of Han Chinese/Southeast Asian ancestry), aplastic anemia/agranulocytosis (rare), teratogenicity. Worsens absence and myoclonic seizures — not used for these seizure types.

