Alcohol is a central nervous system (CNS) depressant, influencing the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Ordinarily, the excitatory (glutamate) and inhibitory (GABA) neurotransmitters are in a state of homeostasis [Figure 1]a. Alcohol facilitates GABA action, causing decreased CNS excitability [Figure 1]b. In the long-term, it causes a decrease in the number of GABA receptors (down regulation). This results in the requirement of increasingly larger doses of ethanol to achieve the same euphoric effect, a phenomenon known as tolerance. Alcohol acts as an N-methyl-D-aspartate (NMDA) receptor antagonist, thereby reducing the CNS excitatory tone. Chronic use of alcohol leads to an increase in the number of NMDA receptors (up regulation) and production of more glutamate to maintain CNS homeostasis [Figure 1]c.