Fluoxetine, sometimes called by its popular brand name Prozac, is a type of antidepressant known as a serotonin specific reuptake inhibitor, or SSRI. These medications prevent the chemical serotonin from being taken from the bloodstream back into cells. Since part of the proposed mechanism for depression and other disorders is an abnormally low level of serotonin in the brain, SSRIs like fluoxetine are thought to help by increasing the amount of serotonin in the brain. However, fluoxetine, like many other medications, has many possible side effects.
Digestive System
Nausea alone, or nausea with vomiting, are especially common side effects of fluoxetine capsules. The pharmacology reference MicroMedex synthesizes the results of several studies when reporting the percentage of patients affected by these side effects; the studies date from the late 1990s because fluoxetine has been in use for many years. One study, for example, which was published in 1997 in the journal "CNS Drugs," found that between 20 and 30 percent of patients taking fluoxetine experience nausea as a side effect. Most often, this is a side effect that gradually either decreases or disappears within the first few weeks of the patient being on the medication. According to the study, up to 3 percent of patients taking fluoxetine may experience vomiting as a side effect; similarly to the nausea, this side effect often resolves within a few weeks.
Mind
Anxiety or just feeling more nervous than usual are two potential side effects of fluoxetine that may occur. The product information for one fluoxetine formulation, Sarafem, reports that up to 14 percent of patients may experience a feeling of increased nervousness, while up to 9 percent may experience a more significant side effect of general anxiety.
A more serious concern relating to fluoxetine capsules is the increased risk of suicidality among children, adolescents and young adults. Like many other antidepressants being sold, fluoxetine carries a black box warning---the most serious warning label the Federal Drug Administration can require of a prescription medication label. The black box warning on fluoxetine warns patients and their families that children, teenagers and young adults up to age 24 are at an increased risk for having thoughts about suicide, which in rare cases may lead to actual attempts at suicide.
Fortunately, this side effect is a rare one. The Sarafem product information, based on a publication from the FDA, reports that 4 percent of pediatric patients taking antidepressants had an increase in suicidal thoughts during their first few months on the medications. However, because of the potentially tragic results of this side effect, it is important for patients and their families to be aware of this possibility. Patients should be monitored by parents, caregivers and physicians for changes in behavior that may indicate suicidal thoughts are developing.
Reproductive System
One of the more potentially bothersome side effects of fluoxetine is that of sexual dysfunction. The product information for Prozac reports that both men and women may experience anorgasmia---an inability to achieve orgasm---or delayed orgasm. The reported frequency of this side effect, reports MicroMedex, ranges quite significantly: Different studies have differing statistics, ranging from about 8 percent of patients experiencing this side effect to 75 percent of patients dealing with sexual difficulties.
References
- FDA: Labeling Change Request Letter for Antidepressant Medications
- FDA: Sarafem Prescribing Information
- Prozac: Prescribing Information
- "CNS Drugs"; Nausea and Vomiting Associated With Selective Serotonin Reuptake Inhibitors: Incidence, Mechanism and Management; P.G. McManis and N.J. Talley; 1997
- MicroMedex: Fluoxetine
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