Fluoxetine is an antidepressant that is used to treat depression. It belongs to a class of antidepressants called selective serotonin reuptake inhibitor (SSRI).It can sometimes be used to treat obsessive compulsive disorder and bulimia. It is believed to have less unwanted side effects than older antidepressants. It takes between 4 to 6 weeks for fluoxetine to work. Prozac is the brand name for Fluoxetine. It can be taken by adults and children who are aged 8 years and over for depression and by adults only for obsessive compulsive disorder and bulimia.