Fluoxetine---also known by the brand names Prozac and Sarafem---is an antidepressant from the selective serotonin reuptake inhibitor class. Prescribed primarily to treat depression and anxiety disorders, fluoxetine may cause weight loss as a side effect in some patients. Because its effects on weight are unpredictable and usually modest, fluoxetine is not routinely prescribed as a weight loss aid. Understanding the relationship between fluoxetine and weight loss allows patients to minimize side effects and choose the best medication for their condition.
Uses
Fluoxetine is approved to treat major depression and pre-menstrual dysphoric disorder, a condition that causes severe mood swings before the menstrual period. It may also be prescribed off-label for patients with obsessive-compulsive disorder, panic attacks and eating disorders like anorexia and bulimia. According to the National Institutes of Health, fluoxetine is less frequently used to treat conditions like obesity, sleep disorders and alcoholism.
Pharmacology
The mechanism by which fluoxetine produces effects is not well understood. It is believed that the drug works by preventing the reuptake of serotonin---a neurotransmitter responsible for regulating mood, appetite and sleep patterns---into platelets. This effect results in higher available levels of serotonin in the brain, leading to improved nerve transmission.
Side Effects
Weight loss is one possible side effect of fluoxetine. According to the American Journal of Psychiatry, acute fluoxetine therapy often results in modest weight loss. Despite this initial effect, patients taking fluoxetine for longer periods often stop losing weight and even re-gain weight as depression symptoms remit. Other common side effects of fluoxetine include headache, sexual dysfunction, anxiety and appetite loss. Not everyone who takes fluoxetine will experience weight loss or other side effects.
Misconceptions
While fluoxetine can be helpful for a minority of patients struggling with depression-induced weight problems, it is not commonly prescribed as a weight loss drug due to its unpredictable effects on weight. According to Mayo Clinic, all antidepressants---including fluoxetine---are capable of causing weight gain. While older antidepressants from the tricyclic family are most likely to cause weight gain, paroxetine and other SSRIs can also trigger weight increase in some patients, making them a poor choice for weight loss in patients without depression.
Considerations
While weight loss may be desirable in some cases, it can also be unhealthy for certain patients. People who experience excessive or sustained weight loss while taking fluoxetine should consult a doctor, who may suggest adjusting the dose or changing to another antidepressant.
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