A serotonin-uptake blocker that is widely used as an antidepressant. Prozac is at once a drug treatment for depression and a bellwether of contemporary attitudes toward the place of psychoactive chemicals in society. Since its introduction in the U.S. in 1987, this drug has revolutionized psychiatry’s approach to the management of depression, inspired cover articles in countless newspapers and magazines, and prompted spirited discussions and debates on radio and television talk shows.

Chemically, Prozac belongs to a class of antidepressants referred to as the selective serotonin reuptake inhibitors (SSRIs). Serotonin is one of the brain’s neurotransmitters, chemical messengers that convey information from one neuron (nerve cell) to the other. This communication takes place by means of the release of a neurotransmitter from one neuron, the passage of the neurotransmitter across the synapse (the junction between neurons), and the attachment of the neurotransmitter to a specific receptor on the receiving neuron. This match between a neurotransmitter and a specific receptor is often compared to the fit of a key in a lock. Starting in the 1960s, researchers developed a series of antidepressant drugs that altered the dynamics of various neurotransmitters within the synapse. In all instances the drugs acted by increasing the amount of neurotransmitter in the synapse or prolonging its actions.