Testing the Effects of Oxybutynin for the Treatment of Hot Flashes in Men Receiving Hormone Therapy for Prostate Cancer

Inclusion Criteria

• Men who are currently receiving androgen deprivation therapy (ADT) for the treatment of prostate cancer. ADT is defined by a history of orchiectomy, or ongoing usage of gonadotropin-releasing hormone agonists or antagonists. Men receiving abiraterone, but not enzalutamide, apalutamide, and darolutamide are eligible, as the latter three are metabolized by CYP3A4 and may affect oxybutynin serum concentrations
• Patients must be on a stable dose of all hormone-directed therapies for at least 28 days prior to registration and must not be planning to discontinue this therapy for at least 42 days following registration. Patients receiving radiation therapy during the study period are eligible
• Eligible patient must have bothersome hot flashes for >= 14 days prior to registration, defined by an occurrence of >= 28 times per week and of sufficient severity to cause the patient to seek therapeutic intervention
• No current use or future planned use of any of the following agents during the study period: drugs that are not Food and Drug Administration (FDA) approved for use in humans, drugs with category X interactions with oxybutynin (e.g. other anti-cholinergic agents, eluxadoline, and potassium chloride), androgens, estrogens, progesterone analogs, gabapentin, cholinergic agonists, cholinesterase inhibitors, or complementary/alternative medicine taken for the purpose of managing hot flashes. No current or future planned use of strong CYP3A4 inhibitors (e.g. antipsychotic agents or macrolide antibiotics) during the study. Prior use of these agents is permitted as long as they are discontinued before registration
• No current or prior use of oxybutynin as a treatment for hot flashes. Prior use of oxybutynin for other purposes (e.g. bladder symptoms) is allowed, as long as the patient has not taken any oxybutynin for 30 days prior to registration
• International Prognostic Scoring System (IPSS) score < 20, unless they have a post void residual confirmation of less than 300 cc residual in the bladder (that is that the patient is eligible with a higher IPSS score if a subsequent postvoid residual [PVR] test looks good)
• Life expectancy of greater than 6 months
• Age >= 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status - 0, 1, or 2
• In order to complete the mandatory patient-completed measures, participants must be able to speak and/or read English

Exclusion Criteria

• Patients with a history of any of the following contraindications to oxybutynin are not eligible: gastroparesis or gastrointestinal obstructive disorders; significant gastric reflux symptoms not controlled by medication; ulcerative colitis; narrow-angle glaucoma; urinary retention requiring indwelling or intermittent self-catheterization within the prior 6 months; hypersensitivity to oxybutynin or any other components of the product; current uncontrolled hyperthyroidism; uncontrolled coronary artery disease or a history of myocardial infarction within the prior 12 months; New York Heart Association (NYHA) class II-IV congestive heart failure; symptomatic cardiac arrhythmias; current uncontrolled hypertension (average systolic > 140 mm Hg and diastolic > 90 mm Hg); myasthenia gravis; or dementia
• Patients with urinary retention requiring indwelling or intermittent self-catheterization within the prior 6 months are not eligible