Zoloft is an antidepressant that is used to treat depression, cost of flagyl pill anxiety and obsessive compulsive disorder. It is a selective serotonin reuptake inhibitor (SSRI) which help to increase the amount cost of flagyl pill serotonin available in the brain. Zoloft produces fewer side effects than older antidepressants called tricyclics, such as Elavil and Tofranil.