Fluoxetine, trade name Prozac, is a selective serotonin re-uptake inhibitor, or SSRI. The Mayo Clinic states that fluoxetine may be used for the treatment of depression, panic disorder, bulimia, obsessive compulsive disorder and premenstrual dysphoric disorder. It can also be included as part of the treatment plan for certain individuals with bipolar disorder. According to "Essential Psychopharmacology," SSRIs work by targeting cells that express serotonin receptors to increase the activity of this neurotransmitter. Because the drug is unable to specifically target only brain cells responsive to serotonin, temporary gastrointestinal upset may be experienced as a side effect.
Nausea
According to a 2001 study published in "BMC Anesthesiology," increased activity of serotonin receptors in the gastrointestinal lining is responsible for nausea and vomiting in patients coming out of surgery. This study confirmed research published in 2000 in "Toxicology" by researchers in Japan implicating elevated serotonin levels as a cause of nausea.
Diarrhea
According to "Essential Psychopharmacology," stimulation of specific types of serotonin receptors in the gastrointestinal tract called 5-HT3 and 5-HT4 receptors can cause increased gastrointestinal motility and cramping. Effectively, this results in food traveling through the gut at a higher speed, resulting in diarrhea and stomach cramps.
Upper Gastrointestinal Bleeding
A 2004 study published in the "Archives of Internal Medicine" found that patients taking SSRIs, such as fluoxetine, had an increased risk of experiencing abnormal gastrointestinal bleeding; medical scientists believe that abnormal bleeding is associated with blood platelet changes caused by inhibition of serotonin re-uptake.
References
- The Mayo Clinic: Fluoxetine
- "Essential Psychopharmacology: Neuroscientific Basis and Practical Applications (2nd Edition)"; Stephen M. Stahl; 2002
- "BMC Anesthesiology"; Treatment of established postoperative nausea and vomiting: a quantitative systematic review; F. Kazemi-Kjellberg et al.; October 2001
- "Toxicology"; Neurochemistry and neuropharmacology of emesis—the role of serotonin; T. Endo et al.; November 2000
- "Archives of Internal Medicine"; Association of Risk of Abnormal Bleeding With Degree of Serotonin Reuptake Inhibition by Antidepressants; Welmoed E. E. Meijer, PhD et al.; November 2004
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