I'm taking two pills now , Roaccutane and also this other pill I have been given along with roaccutane

My first question is about the second pill , what pill is this?
It has DXY100 HD written on it , it is capsule-shaped , and the DXY100 is written on the green part of the capsule and HD is written on the pink.
So yes , the color is green-pink.

My second question concerns Roaccutane , how does Roaccutane shrink the sebaceous glands? and why?