Lacosamide, a newer antiepileptic, exerts its unique mechanism of action by:

• A Blocking T-type calcium channels in thalamic relay neurons
• B Potentiating GABA-A receptor-mediated chloride influx at the benzodiazepine site
• C Inhibiting HCN (hyperpolarisation-activated cyclic nucleotide-gated) channels
• D Enhancing slow inactivation of voltage-gated sodium channels without affecting fast inactivation ✓

Explanation

Lacosamide selectively enhances slow inactivation of voltage-gated sodium channels. Unlike carbamazepine and phenytoin (which enhance fast inactivation), lacosamide stabilises channels in the slow-inactivated state — a distinct conformational state that reduces high-frequency neuronal firing while sparing normal low-frequency activity. This makes it effective in focal seizures with minimal effect on normal neurotransmission. Options B–D describe ethosuximide, benzodiazepines, and ivabradine/gabapentinoids respectively.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.