Adrug that is used to treat seizures functions by preventing inhibitory neurotransmitters from returning to the presynaptic neuron. this slows the rate of neurons firing by increasing the amount of the inhibitory neurotransmitter in the synapse. the drug is most likely to be classified as a

GABA, also called gamma-aminobutyric acid or γ-aminobutyric acid.

Explanation:

GABA (gamma-aminobutyric acid or γ-aminobutyric acid) functions as a neurotransmitter in the central nervous system, decreasing neuron activity thus preventing them from overfiring. In other words, it  is the chief inhibitory neurotransmitter in the developmentally mature mammalian central nervous system. Its principal role is reducing neuronal excitability throughout the nervous system. In humans, GABA is also directly responsible for the regulation of muscle tone. With niacinamide (B3) and inositol, GABA prevents anxiety and stress-related messages from reaching the motor centers of the brain.