Lamotrigine is used as add-on therapy for partial seizures and also in bipolar depression. Its mechanism shared across both indications is:

• A Enhancement of GABA-A receptor chloride conductance
• B Inhibition of MAO-A reducing monoamine degradation
• C Blockade of NMDA receptors at low doses
• D Blockade of voltage-gated sodium channels stabilizing neuronal membranes and reducing glutamate release ✓

Explanation

Lamotrigine blocks voltage-sensitive sodium channels in a use-dependent manner, stabilizing neuronal membranes and reducing repetitive firing. This also leads to decreased release of excitatory glutamate and aspartate from presynaptic terminals. This single mechanism explains both its anticonvulsant and mood-stabilizing (especially antidepressant) properties, as glutamate-mediated excitotoxicity is implicated in both epilepsy and mood disorder pathophysiology.

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

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Written and medically reviewed by the StethoPrep medical team.