Question

Vigabatrin is an inhibitor of

• A. GABA synthase
• B. GABA transaminase
• C. Voltage-gated Na channel
• D. Chloride channel

Hint:

Vigabatrin is used primarily for refractory epilepsy and infantile spasms due to its unique mechanism of increasing brain GABA by inhibiting its breakdown.

Answer 1

The Correct Option is B

Antiepileptic drugs that work through the GABA system either help make more GABA, stop it from breaking down, or act on the receptor it binds to. Vigabatrin's job is to stop GABA breakdown.

1. GABA synthase: This enzyme makes GABA in the first place. Inhibiting it would reduce, not raise, GABA levels, so it does not match vigabatrin's known seizure-reducing effect.
2. GABA transaminase: This enzyme degrades GABA after it has done its job. Vigabatrin permanently disables it, so GABA accumulates instead of being cleared, which is exactly the drug's intended action.
3. Voltage-gated Na channel: A separate class of anticonvulsants targets this channel to prevent neurons from firing repeatedly, unrelated to how vigabatrin functions.
4. Chloride channel: This channel opens in response to GABA binding its receptor, but vigabatrin does not touch the channel directly, it only ensures more GABA is available to act on it.

The enzyme vigabatrin blocks to keep GABA from being degraded is GABA transaminase.

So the correct answer is GABA transaminase.