Which antiepileptic drug exerts its effect by opening neuronal KCNQ (Kv7) potassium channels, thereby stabilising the M-current and reducing membrane excitability?
- A Zonisamide
- B Rufinamide
- C Ezogabine (retigabine) ✓
- D Stiripentol
Explanation
Ezogabine is the first antiepileptic designed as a positive allosteric opener of KCNQ (Kv7) channels underlying the neuronal M-current. Enhancing this potassium current hyperpolarises neurons and limits repetitive firing, giving it a mechanism unique among marketed antiepileptics. Rufinamide prolongs sodium channel inactivity, zonisamide combines sodium channel blockade with weak carbonic anhydrase inhibition, and stiripentol potentiates GABA-C currents and inhibits cytochrome enzymes. Note that ezogabine has been withdrawn from many markets, but its mechanism remains examinable.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.
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Written and medically reviewed by the StethoPrep medical team.