Question

Anticonvulsant drug used as a selective molecular target

• A. Vigabatrin
• B. Gabapentin
• C. Lamotrigine
• D. Tiagabine

Hint:

Drugs targeting voltage-gated ion channels are commonly used in epilepsy. Lamotrigine is especially important due to its dual action in seizure control and bipolar disorder.

Answer 1

The Correct Option is C

Lamotrigine is an anticonvulsant and mood-stabilizing drug primarily used in the treatment of epilepsy and bipolar disorder. Its mechanism of action involves selective molecular targeting of voltage-gated sodium channels (VGSCs), thereby stabilizing neuronal membranes and inhibiting the release of excitatory neurotransmitters like glutamate and aspartate. This selective inhibition reduces the high-frequency neuronal firing associated with seizures, making lamotrigine effective in treating partial seizures, generalized seizures, and Lennox-Gastaut syndrome. - Vigabatrin inhibits GABA transaminase, increasing GABA levels—broad-acting, not highly selective.
- Gabapentin binds to the α₂δ subunit of voltage-gated calcium channels, but it’s not a classic selective target inhibitor.
- Tiagabine inhibits GABA reuptake via GAT-1, increasing GABA in the synaptic cleft—not a selective molecular blocker.
Thus, among the listed drugs, lamotrigine exhibits selective molecular targeting by acting on sodium channels, making it a key GPAT-relevant example of such a mechanism.

Answer 2

The question is looking for the anticonvulsant that works through a clearly defined, selective molecular target rather than a broad or diffuse action on brain chemistry. Comparing how precisely each drug's mechanism is defined narrows it down.

1. Vigabatrin: Vigabatrin irreversibly blocks GABA transaminase, raising GABA levels broadly across the brain. Its effect is widespread rather than aimed at one specific ion channel or receptor subtype.
2. Gabapentin: Gabapentin binds the alpha-2-delta subunit of voltage-gated calcium channels, but its exact downstream effects on neurotransmitter release are still only partly defined, so it is not considered a classic example of clean, selective molecular targeting.
3. Lamotrigine: Lamotrigine binds and stabilizes voltage-gated sodium channels in their inactive state, specifically on rapidly firing neurons. This selectively blocks the repetitive, high-frequency firing that drives a seizure while sparing normal neuronal signaling, making it a textbook case of a defined, selective molecular target.
4. Tiagabine: Tiagabine blocks the GAT-1 GABA transporter to keep more GABA in the synaptic cleft. Like vigabatrin, this raises GABA tone generally rather than acting on one precisely selective target.

Among these four, lamotrigine's action on voltage-gated sodium channels in overactive neurons is the clearest example of a selective molecular mechanism.

So the correct answer is Lamotrigine.