**Question:** Vigabatrin acts by:

A. Increasing GABA synthesis
B. Blocking GABA transaminase
C. Activating GABAA receptors
D. Inhibiting GABA transporter

**Core Concept:** Vigabatrin is an antiepileptic drug primarily used to treat infantile spasms, a type of epilepsy. The drug works by enhancing gamma-aminobutyric acid (GABA) synthesis and inhibiting GABA transaminase, which is the enzyme responsible for breaking down GABA.

**Why the Correct Answer is Right:** Vigabatrin works by inhibiting GABA transaminase (option B), leading to increased GABA levels in the brain and subsequently reducing seizure activity. This mechanism is crucial in treating infantile spasms, as increased GABA levels can help stabilize infantile spasms by reducing neuronal excitability and preventing excessive neuronal firing.

**Why Each Wrong Option is Incorrect:**

A. Increasing GABA synthesis (option A) is not the primary action of vigabatrin. While GABA is involved in the drug's mechanism, inhibiting GABA transaminase is more significant in controlling seizures.

B. Blocking GABA transaminase (option B) is the primary action of vigabatrin, as discussed above.

C. Activating GABAA receptors (option C) is not the primary mode of action for vigabatrin. Although GABAA receptors play a role in GABA's effects, inhibiting GABA transaminase is the primary mechanism.

D. Inhibiting GABA transporter (option D) is not the primary action of vigabatrin. While GABA transporter inhibition contributes to the drug's overall effect, inhibiting GABA transaminase is more crucial in treating infantile spasms.

**Clinical Pearl:** Vigabatrin is a valuable drug in the treatment of infantile spasms, which are a type of epileptic seizure that typically occur in infants and have a significant impact on the child's development. Inhibition of GABA transaminase is the primary mechanism through which vigabatrin achieves its therapeutic effect, leading to increased GABA levels and reduced neuronal excitability.