A woman of childbearing age with juvenile myoclonic epilepsy is counselled against valproate. The preferred alternative levetiracetam exerts its antiepileptic effect through which unique mechanism?

• A Blocking T-type calcium channels in thalamic neurons
• B Enhancing GABA-A receptor function by binding the barbiturate site
• C Binding synaptic vesicle protein SV2A, modulating neurotransmitter release ✓
• D Inhibiting carbonic anhydrase isoforms II and IV

Explanation

Levetiracetam binds with high affinity to synaptic vesicle protein SV2A, a transmembrane protein involved in synaptic vesicle exocytosis. This modulation reduces the rate of vesicle recycling and quantal neurotransmitter release, particularly at high firing frequencies characteristic of epileptic discharges. This mechanism is entirely distinct from all other antiepileptics. T-type calcium channel blockade is the mechanism of ethosuximide (option A); barbiturate site binding is for phenobarbital (option B); carbonic anhydrase inhibition is for topiramate and acetazolamide (option D).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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