Hot flash reduction with oxybutynin

This information came from Rick Davis in the weekly ancan.org newsletter. It’s really worth signing up for just the newsletters. I will be posting a second really informative post from Rick..

Oxy back in heat of the limelight oxybutynin
Old Dog: New Tricks JCO March 26, 2026 an Editorial by AnCan favorite, Dr. Alicia Morgans et al raises a topic addressed in our Reminder for the Jan 19, 2026 meeting - oxybutynin as an antidote to hot flashes. Ironically, just a few days after that, Dr. Brad Stish published his Alliance trial in JCO that offered a definitive correction.
Bottom line - based on Dr. Stish's Mayo trial of 80 men, oxybutynin achieved great results using oxy to reduce hot flashes for men on hormone therapy. Depending on the dose, up to 80% of men experienced a 50% reduction.
Here's the important piece of information revealed in Dr. Stish's article that was unclear in the published abstract and clinical trial information. Of the 80 trial participants only 24 (30%) were on doublet therapy with abiraterone + ADT. The remainder were all on singlet ADT alone. The lutamide Brothers were excluded.
That doesn't mean oxy only works with abi. We know it works with apalutamide from the experience of our Canadian AnCan'r who tried it with success. The dosage required with apalutamide. darolutamide or enzalutamide may be lower because of interference from the CYP3A4 pathway. Oxy has significant side effects laid out in our earlier post and below, so this should be taken seriously.
From hereon out, we can advise our Gents on ADT alone to discuss oxybutynin with their Providers. If you're on doublet with abi, we know it works; if you're on doublet with an lutamide Brother, it works but the dose is unclear.
Not published was whether including the abi changed the results.
In follow up correspondence with Dr. Morgans, she mentions that her clinic has prescribed oxy for all ARSI with around 40-50% success. While her editorial referenced estradiol (E2), making our Emperors smile no doubt, it failed to mention that supplementary E2 may address hot sweats.
And in deference to Dr. Paul, and Dr. John, who always considers Adverse events, we're obliged to mention that oxy can cause dry mouth, constipation and occasional urinary retention. Nothing comes without a cost!