Carbamazepine is used for trigeminal neuralgia. Its mechanism of action is:

Correct answer: C. Sodium channel blocker

• A. GABA receptor agonism describes benzodiazepines and barbiturates, not carbamazepine.
• B. Potassium channel blockers are used in a different pharmacological context (e.g., some cardiac arrhythmias); not the mechanism of carbamazepine.
• C. Correct. Carbamazepine blocks voltage-gated sodium channels, stabilizing neuronal membranes and reducing repetitive firing. This is the basis for its anticonvulsant and analgesic effects in trigeminal neuralgia.
• D. T-type calcium channel blockers (e.g., ethosuximide) are used for absence seizures — not carbamazepine's mechanism.