Finpecia is a generic version of Propecia and this contains 1mg of Finasteride and if you want to take 1mg a day just take 1 tablet.
Fincar is a generic version of Proscar and this contains 5mg's of Finasteride people like to cut this up into 4 bits for a 1.25mg dose or 5 bits for a 1mg dose but you may cut it into any dose you like!
Now for the reasons that they do this.
Propecia: This tablet is usually taken by people who don't trust generics or can't get them and does not trust cutting the pills up or cannot be bothered to. They also might be a person on a prescription from a doctor.
Proscar: This is also taken by people who don't trust generics but would like to save money and or change there dose. They may also have a prescription from a doctor that they have talked into letting them because it's the same drug just cheaper.
Finpecia: The people that take this tablet do not have a trust issue with generics but do not like to cut pills up for various reasons and still would like to save money over Propecia and sometimes Proscar (which is around the same price range depending on the dose you take).
Fincar This is the ultimate in cost cutting, it's a generic and you are getting 5mg in one pill. The people that take these are really trying to save money and or are not happy with taking 1mg and don't mind cutting a pill up.
But in my opinion they are all Finasteride and people being people take them for there different reasons.
Ps If you come across any other generic version of Finasteride just run them through the search button in the forum.
