I'm on Propecia and Regaine the foam for about 6 months.
1.5 months ago I experienced a bad shed which lasted till recently and I was scared as I thought that there would be only one shedding phase, which is when I started the med. Now I'm better and shed less than before. But I'm not sure which causes this shed.
Anyway, I've done some searching and it seems that one goes through multiple shedding phases when uses those meds.
Good luck