Hot flashes can interrupt a meeting, wake someone repeatedly or make endocrine treatment feel harder to live with. Being told they are expected does not make them easier.
One option worth knowing is oxybutynin, a prescription anticholinergic medicine used for bladder symptoms. Its use for hot flashes is off-label. That can still be evidence-based; it simply makes a clear discussion of benefits and trade-offs important.
Evidence at a glance
Studied population: women with frequent hot flashes, including many taking breast cancer endocrine therapy. Intervention: oral oxybutynin versus placebo. Potential benefit: fewer episodes and less interference with daily life. Main limits: short follow-up, missing data and anticholinergic side effects.
What the randomized trial found
The 2019 ACCRU trial randomized 150 women with at least 28 hot flashes weekly. Sixty-five percent were taking tamoxifen or an aromatase inhibitor. Researchers tested oral oxybutynin 2.5 mg twice daily, 5 mg twice daily or placebo over six weeks. These are research doses, not instructions to self-treat.
Daily hot-flash frequency fell by an average of 4.8 episodes with the lower dose, 7.5 with the higher dose and 2.6 with placebo. That is roughly 2.2 or 4.9 fewer daily episodes beyond placebo: a potentially worthwhile difference.
However, only 113 participants were evaluable for the primary endpoint. Six weeks cannot establish years of effectiveness or cognitive safety. Dry mouth was reported by study staff in 21%, 33% and 7% of the lower-dose, higher-dose and placebo groups, respectively.
What newer evidence adds
A 2026 ASCO systematic-review abstract identified five studies across cancer-related and menopausal symptoms. It reported fewer hot flashes with oxybutynin, but more discontinuation because of adverse effects. This is conference-level evidence across mixed populations, not a new large breast cancer trial. It reinforces the trade-off without settling long-term safety.
Where it belongs among the options
The 2023 Menopause Society position statement includes oxybutynin among supported nonhormonal treatments. It also supports cognitive behavioral therapy, clinical hypnosis, certain antidepressants and gabapentin. The best choice depends on other symptoms, medicines and preferences; the oxybutynin trial did not prove superiority to these alternatives.
The same statement does not recommend supplements or herbal remedies for hot flashes because the evidence is insufficient or inconsistent. That is a useful reminder for integrative care: being willing to discuss a botanical also means being willing to discuss a prescription or behavioral treatment when the evidence is stronger.
Safety deserves more than a footnote
The prescribing information warns about constipation, blurred vision, drowsiness and confusion. Reduced sweating can increase heat-related illness risk. Urinary retention, gastric retention and uncontrolled narrow-angle glaucoma are contraindications.
Other medicines with anticholinergic effects can add to these problems. A pharmacist should review the whole list, particularly when memory concerns, frailty, dry mouth or constipation are already present. New confusion or difficulty urinating deserves prompt clinical advice.
Questions for the care team
- Could we track hot-flash frequency and sleep disruption before choosing treatment?
- Would a behavioral approach, oxybutynin or another nonhormonal medicine fit best?
- Do my other medicines add anticholinergic effects or create interactions?
- When will we reassess benefit, side effects and whether to continue?
This evidence concerns symptom relief, not cancer control. If hot flashes are making endocrine treatment difficult, bring that into the conversation before changing or stopping it. A tolerable plan is worth working on together.
Evidence checked October 7, 2026. Educational review; individual treatment decisions belong with your care team. Explore the Missing Script article library and the podcast—coming soon.
