The drug Effexor (venlafaxine hydrochloride) was approved by the FDA in 1993 for the treatment of depression and anxiety. An extended-release once-daily version, Effexor XR, received marketing clearance in 1997. Now Effexor XR is showing promise for ameliorating the symptoms of another disorder: diabetic neuropathy. The results of the study were reported at the 60th annual meeting of the American Diabetes Association in June 2000.
Diabetic neuropathy causes numbness, tingling and pain in the arms and legs due to diabetes-associated nerve damage, and it afflicts some 60 percent of patients with diabetes. In doses ranging from 150-225 mg/day, Effexor XR was significantly more effective than placebo in relieving neuropathic pain. The drug is manufactured by Wyeth-Ayerst Laboratories, a division of American Home Products. Effexor inhibits the uptake of the neurotransmitters serotonin and norepinephrine in the brain. Both serotonin and norepinephrine are involved not only in mediation of mood, but also perception of pain.
The safety and effectiveness of Effexor XR as a treatment for painful diabetic neuropathy were assessed in a study of 244 patients age 18 or older with type 1 or type 2 diabetes who received either Effexor XR 75 mg, 150-225 mg or placebo for up to six weeks. Ratings of pain relief by patients and investigators were used to measure treatment effectiveness.
Effexor XR 150-225 mg produced significantly greater pain relief compared with placebo. By week six, 56 percent of patients treated with Effexor XR 150-225 mg experienced significantly lowered pain intensity compared with 39 percent treated with Effexor XR 75 mg and 34 percent given a placebo. Since patients with a major depressive disorder were excluded from the study, the improvement of symptoms was attributable to a pain-relieving, rather than an antidepressant, effect.
“As diabetic neuropathy progresses over time, the pain caused by nerve damage may become overwhelming, and medications such as aspirin, acetaminophen or ibuprofen do not work as well,” said Dr. Sherwyn Schwartz, director of the diabetes and glandular disease clinic in San Antonio, Texas. “Effexor XR is an effective medication that may represent a new treatment option for patients suffering from this condition.”
The most common adverse event associated with Effexor XR was nausea. Other side effects that may occur with use of Effexor XR include insomnia, nervousness, anorexia, weight loss and blood pressure increases.