Cymbalta, a brand name for the generic serotonin-norepinephrine reuptake inhibitor known as duloxetine, was initially approved by the U.S. Food and Drug Administration in 2004 for the treatment of major depression and generalized anxiety disorders. Subsequently, Cymbalta earned designations for the treatment of fibromyalgia and neuropathic pain in people with diabetes. The latter applications have spurred interest in Cymbalta as a treatment for abdominal pain due to irritable bowel syndrome, or IBS.
Therapeutic Rationale
According to Dr. Chung Owyang, chief of gastroenterology for the University of Michigan Health System and author of the chapter on IBS in the 2008 edition of "Harrison's Principles of Internal Medicine," selective serotonin reuptake inhibitors, known as SSRIs, appear to decrease gut transit time in people with constipation-predominant IBS, and reduce abdominal and rectal pain sensations. Theoretically, serotonin-norephinephrine reuptake inhibitors offer all the benefits of SSRIs, plus, additional benefits from enhanced availability of norepinephrine.
Dosing & Administration
When used to treat IBS, doctors prescribe Cymbalta as a once-daily oral dose of 60 mg. In some cases, patients may start with a 30 mg dose for a few weeks, in order to reduce the risk of side effects.
Side Effects
According to the FDA, the most common side effects of Cymbalta are nausea, dry mouth, constipation, sleepiness, increased sweating and decreased appetite. Most side effects subside within one to four weeks. Patients with persistent or severe side effects should talk to their doctors.
Precautions
According to the FDA, patients taking Cymbalta may have increased risk of bleeding, especially if they also regularly use non-steroidal anti-inflammatories, such as aspirin, or other drugs that affect coagulation. Patients with a history of liver or kidney disease, diabetes, bipolar disorder, high blood pressure and glaucoma should talk to their doctors about the risks and benefits of Cymbalta prior to starting treatment.
Warnings
Patients who take other antidepressant medications should discontinue use at least two weeks before starting Cymbalta due to the risk of a medical emergency known as serotonin syndrome. Signs and symptoms of serotonin syndrome include increased body temperature, hallucinations, loss of coordination, nausea, vomiting, overactive reflexes, changes in heart rate and blood pressure and, ultimately, coma. Serotonin syndrome can also occur when patients combine prescription migraine medications known as triptans with Cymbalta; these patients should ask their doctors for additional instructions.
Effectiveness
As of August 2010, the National Library of Medicine lists only one clinical trial evaluating the effectiveness of Cymbalta in patients with IBS. In that study, published in the journal "Human Psychopharmacology," researchers at McLean Hospital in Belmont, MA found that treatment with Cymbalta conferred clinically and statistically significant improvements in pain, severity of illness, quality of life, loose stool, work and family disability and anxiety in IBS patients who took the drug for 12 weeks. However, nearly half--seven out of 15--of the study's participants withdrew before the study was completed, citing side effects of Cymbalta.
References
- Irritable Bowel Syndrome (Chapter); C. Owyang; In: "Harrison's Principles of Internal Medicine, 19th ed.;" A.S. Fauci et al. (Eds.); 2008
- The University of North Carolina School of Medicine: The Use of Antidepressants in the Treatment of Irritable Bowel Syndrome
- "Human Psychopharmacology;" Duloxetine in the Treatment of Irritable Bowel Syndrome; B.P. Brennan et al.; Jul. 2009
- Food and Drug Administration: Cymbalta (Duloxetine Hydrochloride) Delayed-Release Capsules for Oral Use
