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 treatmentof prostate cancer. ADT is defined by a history of orchiectomy, or ongoing usage ofgonadotropin-releasing hormone agonists or antagonists. Men receiving abiraterone,but not enzalutamide, apalutamide, and darolutamide are eligible, as the latterthree 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 28days prior to registration and must not be planning to discontinue this therapy forat least 42 days following registration. Patients receiving radiation therapy duringthe study period are eligible

• Eligible patient must have bothersome hot flashes for >= 14 days prior toregistration, defined by an occurrence of >= 28 times per week and of sufficientseverity to cause the patient to seek therapeutic intervention

• Life expectancy of greater than 6 months

• Eastern Cooperative Oncology Group (ECOG) performance status - 0, 1, or 2

• In order to complete the mandatory patient-completed measures, participants must beable to speak and/or read English

Exclusion Criteria:

• No current use or future planned use of any of the following agents during the studyperiod: drugs that are not Food and Drug Administration (FDA) approved for use inhumans, androgens, estrogens, progesterone analogs, gabapentin, selective serotoninreuptake inhibitor (SSRI)/serotonin and norepinephrine reuptake inhibitor (SNRI)anti-depressants, cholinergic agonists, cholinesterase inhibitors, orcomplementary/alternative medicine taken for the purpose of managing hot flashes.Prior use of these agents is permitted as long as they are discontinued beforeregistration

• No current or prior use of oxybutynin

• Patients with a history of any of the following contraindications to oxybutynin arenot eligible: gastroparesis or gastrointestinal obstructive disorders; significantgastric reflux symptoms not controlled by medication; ulcerative colitis;narrow-angle glaucoma; urinary retention requiring indwelling or intermittentself-catheterization within the prior 6 months; hypersensitivity to oxybutynin orany other components of the product; current uncontrolled hyperthyroidism;uncontrolled coronary artery disease or a history of myocardial infarction withinthe prior 12 months; New York Heart Association (NYHA) class II-IV congestive heartfailure; symptomatic cardiac arrhythmias; current uncontrolled hypertension;myasthenia gravis; or dementia