Carbamazepine exerts its anticonvulsant effect by acting on which ion channel?

Correct answer: D. Voltage-gated sodium channels

• A. ❌ Potassium channel openers such as retigabine are a different drug class.
• B. ❌ Calcium channel modulation is the mechanism of ethosuximide (T-type) and gabapentin/pregabalin (α2δ subunit).
• C. ❌ Chloride channel enhancement via GABA-A is the mechanism of benzodiazepines and barbiturates.
• D. ✅ CORRECT — Carbamazepine blocks VOLTAGE-GATED SODIUM CHANNELS in their inactivated state, prolonging inactivation and preventing high-frequency repetitive firing. This is also why it is first-line for trigeminal neuralgia.

Note: Dental relevance: carbamazepine is a potent CYP3A4 INDUCER and causes agranulocytosis/aplastic anemia, hyponatremia, and Stevens-Johnson syndrome (HLA-B*1502 screening in Asian patients).