Oxybutynin use as a hot flash reducer in breast cancer survivors in the use of tamoxifen: a pilot randomized clinical trial

Introduction: Breast cancer is a heterogeneous disease in which genetic and environmental factors are involved. The most prevalent types are those expressing hormone receptors, consisting of 60% to 70% of all cases in developed countries. Therefore, the most common type of therapeutic approach is hormone therapy. Estrogen blockers, such as tamoxifen, and aromatase inhibitors, such as anastrozole, are the most prescribed medicines for these types of cancer. The purpose of this article was to assess the effects of once-daily oxybutynin 5 mg on frequency and severity of hot flashes in women with breast cancer using tamoxifen. Methods: A two-month double-blind, placebo-controlled, pilot randomized clinical trial in women with breast cancer using tamoxifen that were experiencing hot flashes. These women were treated daily with oxybutynin 5 mg (n=11) or a placebo (n=12). The co-primary outcome was to reduce, from baseline to month two, the frequency and severity of hot flashes symptoms. Results: Reductions in both frequency and severity of hot flashes were observed in women who received oxybutynin 5 mg/day compared to placebo, even though it was not statistically significant. Adverse effects reported by the oxybutynin arm were tachycardia and decrease in appetite (9.1%), and in the placebo arm were headaches (8.3%), xerostomia (16.6%), diarrhea (8.3%), and dry skin (8.3%). Conclusions: oxybutynin is a safe nonhormonal therapy for hot flashes in women with breast cancer using tamoxifen.