If you take 1mg full pill you should be fine. But if you take generic proscar I would err on the side of caution. FDA regulates the entire process during drug approval which includes the manufacturing process to make sure the pill has the right amount of active ingredient when it comes to the initial approval for brand name. The process that brand name companies take is more expensive but guarantees the uniformity of the pill, meaning if you split it it will likely have a similar amount of ingredient between pieces. Even different fillers/binders can change the uniformity of the pill because it is not as soluble among other things. Generics are only tested for bio-equivalency. This means that the pill can have less ingredient it won't matter as long as it is bioequivalent. Their pill manufacturing process is not tested, they don't have to make sure each pill is EXACT. It can have less ingredient too but it doesn't matter because it only requires 80% equivalency. The manufacturing process is cheaper as it doesn't need to be super uniform so it can end up that the pill is not evenly distributed and 1 side of the pill has all the active ingredient. So yah I only get proscar in brand name, but for propecia it wouldn't matter other than the missing 20% of the ingredient that is possible.
