Topiramate is a broad-spectrum antiepileptic whose mechanism of action includes which of the following?
- A Blockade of AMPA and kainate subtype glutamate receptors combined with weak carbonic anhydrase inhibition ✓
- B Blockade of NMDA receptor glycine site combined with enhancement of adenosine signalling
- C Selective potentiation of GABA-B receptor function combined with T-type calcium channel blockade
- D Irreversible inhibition of GABA transaminase combined with sodium channel blockade
Correct answer: A. Blockade of AMPA and kainate subtype glutamate receptors combined with weak carbonic anhydrase inhibition
Explanation
Topiramate blocks AMPA and kainate receptors, thereby reducing excitatory glutamatergic transmission, and it also weakly inhibits carbonic anhydrase. The latter explains its adverse effects of paraesthesias, nephrolithiasis and metabolic acidosis. Clinically it causes weight loss rather than gain and can produce word-finding difficulty and cognitive slowing. Option D describes vigabatrin, and pure T-type calcium channel blockade describes ethosuximide, so both are mechanistically wrong for topiramate.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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