A pill used to treat an overactive bladder can also be used to reduce hot flashes among men taking hormone-deprivation therapy for prostate cancer.

Men taking oxybutynin had a dramatic decrease in the number and intensity of hot flashes that occurred as a result of their prostate cancer treatment, researchers reported Feb. 2 in the Journal of Clinical Oncology.

“Oxybutynin demonstrated clear and clinically meaningful improvements in both hot flash frequency and quality of life for men undergoing hormone therapy for prostate cancer,” said lead researcher Dr. Bradley Stish, a radiation oncologist at the Mayo Clinic in Rochester, Minnesota.

“These results provide strong support for its use as an effective management option for this challenging and often overlooked side effect of prostate cancer treatment,” Stish said in a news release.

Hormone therapy is an effective treatment against prostate cancer, lowering levels of male hormones like testosterone that fuel cancer cells.

However, the therapy causes hot flashes in up to 80% of men taking it, leading to fatigue and bad sleep, researchers said in background notes. These side effects often cause patients to stop taking their meds.

Previous studies have shown that oxybutynin can significantly reduce hot flashes among women, so researchers figured the drug might have a similar effect among men.

For the new study, researchers recruited 88 men with an average age of 68, and randomly assigned them to one of three groups. Two groups took either a high or low dose of oxybutynin daily, and the third took a placebo.

Researchers found that men on the high dose of oxybutynin had the largest improvements, with nearly seven fewer hot flashes daily and a 14-point reduction in hot flash severity on a scale running from 0 to 100.

By comparison, men on a placebo had two fewer hot flashes daily and a 5-point drop in hot flash severity, and men on the low dose of oxybutynin had nearly five fewer hot flashes daily and a 10-point drop in severity.

Improvements also occurred quickly, often during a man’s first week taking the pill, researchers said.

The share of patients who achieved at least a 50% reduction in their hot flash scores also was higher among oxybutynin patients — 79% in the high-dose group and 57% in the low-dose group, versus 32% taking a placebo.

“These results are incredibly encouraging,” Stish said. “Men with hot flashes from hormone therapy now have another therapeutic option available to help reduce their symptom burden."

He said future research will look to learn more about hot flash therapy options in these patients.