Woman holding a capsule of the drug Prozac in her mouth. Prozac (fluoxetine hydrochloride) is an anti-depressant medication. Each green and yellow capsule contains 20mg of the drug. Prozac inhibits the uptake of the chemical serotonin, a neurotransmitter that is thought to regulate mood and be involved in sleep and sensory perception. In depressive illness, the typical dose of Prozac is 20mg daily and up to 60mg for sufferers of bulimia nervosa. Anti-depressant drugs usually take at least 10 days to have any beneficial effect.