White Xanax Bars are benzodiazepine drugs that enhance the effects of the neurotransmitter Gamma-aminobutyric acid or GABA. It is an inhibitory neurotransmitter that blocks or reduces the transfer of chemical signals, including initiating, sending, and receiving messages via synapses from one nerve cell to the next. Low GABA levels in the central nervous system, which includes the brain and spinal cord, indicate anxiety, stress, and epilepsy.