A drug commonly used to treat depression and anxiety disorder was effective at reducing joint and muscle pain associated with a breast cancer treatment, according to a study from the University of Michigan Comprehensive Cancer Center.

The women in the study were taking aromatase inhibitors, a type of drug designed to block the production of estrogen, which fuels some breast cancers. About half of women taking these drugs experience aches and pains in their joints and muscles that cannot be adequately relieved by over-the-counter painkillers. Up to 20 percent of these women will stop taking an aromatase inhibitor because of this pain.

"Since women typically take these drugs for five years, it is important that the side effects not interfere too much with their quality of life, or they will be less likely to continue taking the medicine, which may lead to a greater chance of their breast cancer returning," says study author N. Lynn Henry, M.D., Ph.D., assistant professor of internal medicine at the U-M Medical School.

Henry presented the initial results of the study Dec. 11 at the 33rd Annual San Antonio Breast Cancer Symposium.

The study looked at the drug duloxetine, or Cymbalta, which is used to treat depression and generalized anxiety disorder. It's also been shown to work in multiple other chronic pain conditions, such as fibromyalgia and, more recently, osteoarthritis. It is believed to decrease pain through its actions in the central nervous system.

Of 29 patients evaluated, nearly three-quarters reported that their pain had decreased by at least 30 percent. On average, after eight weeks of treatment, pain scores declined 61 percent. Only one in five patients stopped taking duloxetine because of side effects.

"Duloxetine appears to be effective at reducing the muscle and joint pain many women experience from aromatase inhibitors, with only mild additional side effects," Henry says.

The researchers are planning a randomized, controlled trial comparing duloxetine to placebo. Henry is also doing research looking at the effect of aromatase inhibitors on pain perception to better understand why women develop pain.

Additional U-M authors: Mousumi Banerjee, Ph.D., Dorothy Blossom, Max Wicha, M.D., Catherine Van Poznak, M.D., Jeffrey Smerage, M.D., Ph.D., Anne Schott, M.D., Jennifer Griggs, M.D., M.P.H., and Daniel Hayes, M.D.
The study was supported by an Investigator Initiated Grant from Lilly Pharmaceuticals.