A patient with newly diagnosed focal epilepsy is started on lacosamide. Its unique mechanism of action compared to phenytoin involves:
- A Blocking fast inactivation of sodium channels
- B Selectively enhancing slow inactivation of voltage-gated sodium channels ✓
- C Blocking T-type calcium channels in thalamic neurons
- D Inhibiting carbonic anhydrase
Correct answer: B. Selectively enhancing slow inactivation of voltage-gated sodium channels
Explanation
Lacosamide selectively enhances the slow inactivation state of voltage-gated sodium channels, reducing sustained repetitive firing without affecting the fast inactivation state. This differentiates it mechanistically from carbamazepine and phenytoin, which primarily stabilize the fast inactivation state. T-type calcium channel blockade is the mechanism of ethosuximide; carbonic anhydrase inhibition is the mechanism of acetazolamide.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.