Lamotrigine is used as add-on therapy in a patient with partial seizures refractory to carbamazepine. Which statement about lamotrigine's pharmacology is CORRECT?
- A It blocks voltage-gated sodium channels by preferentially binding the inactivated state and also inhibits glutamate release ✓
- B It primarily blocks T-type calcium channels with no effect on sodium channels
- C It irreversibly inhibits GABA transaminase, raising synaptic GABA levels
- D Its half-life is unaffected by concurrent enzyme-inducing antiepileptics
Correct answer: A. It blocks voltage-gated sodium channels by preferentially binding the inactivated state and also inhibits glutamate release
Explanation
Lamotrigine blocks voltage-sensitive sodium channels by preferentially binding their inactivated (use-dependent) state, thereby reducing high-frequency neuronal firing. Additionally, it inhibits presynaptic release of excitatory amino acids, particularly glutamate and aspartate. Its half-life is markedly shortened by enzyme inducers like carbamazepine and phenytoin, necessitating dose adjustment.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.