Optimizing Oxybutynin Doses for ADT-Induced Hot Flashes in Prostate Cancer

Although 5 mg of oxybutynin (Ditropan) conferred the most efficacious outcomes among patients experiencing hot flashes related to androgen deprivation therapy exposure for prostate cancer treatment, there may be instances where the 2.5-mg dose may be preferred.

In a conversation with CancerNetwork®, Bradley J. Stish, section head of Radiation Oncology and radiation oncologist specializing in genitourinary cancers at Mayo Clinic, discussed the clinical rationale for the dose selection of oxybutynin for hot flash symptom management in prostate cancer treatment. He specifically highlighted key circumstances where a reduced dose of 2.5 mg may be warranted for select patients.

Touching upon the collaborative nature of decision-making between physicians and patients, he emphasized that the adverse effect (AE) profile of oxybutynin is predictable, as patients who show dry mouth or constipation symptoms at baseline are suggested to start at the lower dose level before potentially increasing the dose if symptoms are managed. Furthermore, he explained that patients who start on the 5-mg dose and experience cumbersome AEs have the option to move to the reduced 2.5-mg dose.

Transcript:

When we’re thinking about which dose to clinically use in patients, the study provided us with good data that are open to flexibility for both patients and physicians or providers. If you’re trying to get the biggest bang for your buck in terms of reduction of hot flash symptoms, 5 mg twice daily was the clear winner in our study. But we still saw a meaningful improvement in many symptoms with the 2.5-mg twice-daily dose.

Many times, this becomes a discussion between the physician and the patient regarding their goals of treatment, and whether there are any specific factors in their case that may make you inclined to consider a lower dose. We know some of the [adverse] effects of the drug can be pretty predictable—things like dry mouth or constipation—and if there’s a patient who may have baseline symptoms in both of those domains, it may be wiser to start at a lower dose and see if you can get an effect that’s desirable. You can always increase that dose if the effect isn’t quite what was hoped originally. Similarly, if we have patients who start at the 5-mg twice-daily dose, and we’re seeing [adverse] effects that are bothersome or prohibitive, physicians can feel comfortable decreasing that dose in half. Having that flexibility is nice for both patients and physicians to ensure that they can find the right dose for their specific situation.

Reference

Stish BJ, Mazza GL, Nauseef JT, et al: Oxybutynin versus placebo for the treatment of hot flashes in patients receiving androgen-deprivation therapy for prostate cancer. J Clin Oncol. Published online January 26, 2026. doi:10.1200/JCO-25-01486