I dunno man. I'm not even sure how they produce tablets.
Here's my analogy - and forgive me, but it's the best I can come up with since I just woke up.
Let's say you're making chocolate chip cookies (wow, this is going to sound stupid) and each has ten chips in it and the rest is cookie dough (I really ought to shut up now). Let's say they are produced on a conveyor belt. Well, each cookie will have the ten chips, but they are at random spots in the cookie. If you divide it up into fourths, each section will have a different amount of chips.
I assume that's similar to the 5mg Proscar production. Each tablet has 5mg of finasteride but because the rest of the tablet is filler, the finasteride is distributed differently in each one. I mean, they made the pill so you could consume it whole - I don't think they were anticipating people splitting it up into fourths, so distributing the finasteride evenly in each one wasn't a concern of theirs.
And might I add, that analogy is probably the dumbest thing I've ever written. Maybe it's not my hair I'm losing but my mind instead. Apologies if I am waaaaaayyyyy off the mark.
Does anyone know have a good link to find out how tablets are produced?