Fluoxetine hydrochloride is an antidepressant drug used medically in the treatment of depression, obsessive-compulsive disorder, bulimia nervosa, premenstrual dysphoric disorder and panic disorder. Fluoxetine is also used to treat many other conditions, such as ADHD. It is sold under the brand names Prozac®, Symbyax®, Sarafem®, FLUX®, Fontex®, Foxetin®, Ladose®, Fluctin®, Prodep®, Fludac®, Oxetin and Lovan®. Fluoxetine was derived from diphenhydramine, an antihistamine found to inhibit reuptake of the neurotransmitter serotonin. Compared to other popular selective serotonin reuptake inhibitors (SSRIs), fluoxetine has a strong energizing effect. This makes fluoxetine highly effective in treatment of clinical depression cases where symptoms like depressed mood and lack of energy prevail. Although stimulating, it is also approved for a variety of anxiety disorders, including panic disorder and obsessive compulsive disorder. Prozac was approved by the FDA on December 29, 1987 and introduced in the US at the beginning of 1988. The drug became very popular, with millions around the world having taken the medication. In the fall of 2001, Eli Lilly lost a patent dispute with Barr Laboratories and now fluoxetine hydrochloride is manufactured by many companies. Prozac's popularity and selling success has been aided greatly by Lilly's extensive marketing campaign for the drug, considered one of the most successful in the history of American pharmaceuticals. Fluoxetine hydrochloride is approved in the United States to treat depression, obsessive-compulsive disorder, bulimia nervosa, premenstrual dysphoric disorder and panic disorder. In the United Kingdom, it is approved to treat depression with or without anxiety, bulimia nervosa, and obsessive-compulsive disorder. In December 2003 the FDA approved Symbyax® to treat bipolar depression. Symbyax is a combination of fluoxetine and olanzapine. (However, the pure form of fluoxetine can cause mania, mixed-states, rapid cycling and psychosis in bipolar patients, particularly if the patient is not also taking a mood stabilizer.) Common adverse effects include anxiety, which is possibly associated with an interaction of fluoxetine with the pineal gland, in addition to restlessness and insomnia. Weight loss, trembling, weakness, skin rash, anorgasmia, itching, and a decrease in sexual drive, have also been reported. Finally it has been reported to cause subsequent weight gain. Like other SSRIs, an overdose of fluoxetine or combining it with other antidepressants can lead to serotonin syndrome. Fluoxetine is eliminated very slowly by the body. The half-life of fluoxetine after a single dose is two days and, after multiple dosing, four days. The liver then metabolizes fluoxetine into norfluoxetine, a desmethyl metabolite, which is also a serotonin reuptake inhibitor; norfluoxetine has an even longer half-life, i.e. 8.6 and 9.3 days for single and repeated dosage respectively. These long half-lives may be helpful in those patients with compliance issues, but fluoxetine is most effective when taken daily. Other SSRIs have, by comparison, a very short half-life. Some professionals feel that it is fluoxetine's long half-life that gives it much of its therapeutic utility, however this has never been proven under rigorous scientific study. Nevertheless, its long half life is also relevant because suddenly discontinuing SSRIs is known to produce both somatic and psychological withdrawal symptoms, a phenomenon known as "SSRI discontinuation syndrome". It is generally accepted that fluoxetineґs withdrawal symptoms are much smoother than with other SSRIs, as the substance takes several days to completely leave the system. Fluoxetine is a potent CYP2D6 inhibitor, which can decrease metabolism of other medications. Disclaimer The information presented here should not be interpreted as medical advice. Please consult with your physician before taking this or any other drug. Permission is granted to reprint this article as long as no changes are made, and the entire resource box is included.