Eli5: what is the difference between a generic drug to the original drug, and why do some doctors will swear by the original drug?

Question

Eli5: what is the difference between a generic drug to the original drug, and why do some doctors will swear by the original drug?

In: 1046

Answer 1

A major missing point in the discussion is something called crystal polytypes. When making a solid, the drug molecules can sometimes pack together in different patterns. These differing stacking patterns may dissolve slower or faster in the body changing how you body absorbs the drug molecule. So not only does the molecule have to be identical (that is fda regulated) but the crystal structure and crystal size should be the same which can be very difficult to control and replicate by generics in some cases.