Im courious basically. Does finasteride break a fast?
The weight loss aspect of the fast? No.
The autophagy aspect of the fast? Maybe. The science isnt clear about what breaks the repair phase of a fast. Some say ANYTHING that isnt water. Some say only things that have calories. Some say only things with protein. So for now, its really unknown.
What are you taking it for? And how long? I took it for 2 weeks for teeth grinding and found it worked perfectly for 1 week. After that it required double the dose to keep me grind free. I cant imagine taking it for long term seeing how quickly your body can adapt to it.