Hot Flash Drug May Interfere with Cancer Therapy

Release Date:
NIGMS Communications Office

Tamoxifen (Nolvadex®) is an effective therapy for some types of breast cancer. However, roughly 80 percent of women who take the drug experience hot flashes. While not life-threatening, hot flashes can be so uncomfortable that people stop taking the medicine. To make this cancer-controlling drug tolerable, doctors can treat Nolvadex-triggered hot flashes with antidepressants such as paroxetine (Paxil®).

New evidence hints that taking both drugs together may not be such a good idea. David A. Flockhart, M.D., Ph.D., of the Indiana University School of Medicine in Indianapolis knew that the body uses the same enzyme to break down Nolvadex and Paxil. He therefore wondered whether taking both drugs together might affect blood levels of either or both of them. To test this, Flockhart performed a study with 12 breast cancer survivors who had been taking Nolvadex for at least 1 month and were having severe hot flashes. He gave Paxil to the study volunteers for 4 weeks and then took blood samples.

Women who took both drugs at the same time had substantially lower levels of a key byproduct of Nolvadex, chemical evidence that Paxil does affect how the body processes Nolvadex. But the effects differed among the women depending on their innate capacity to process drugs, which helps explain why Nolvadex's effectiveness can vary among people. Flockhart cautions that further data are needed to determine if treatment recommendations should be altered as a result of his study.

Writer: Alison Davis, Science Writing Contractor