Isotrue 20 mg. The capsule belongs to a class of medications known as retinoids (vitamin A derivatives). It is used to treat severe acne that has failed to respond to previous therapies. Isotrue 20 mg. Capsules help to treat acne by lowering the production of sebum (a natural material that causes acne). This destroys acne-causing germs and keeps spots or pimples from forming. It normally takes a few weeks to show results, so maintain taking it even if it does not appear to be working. Acne may worsen before it improves, but with good treatment, your skin will become clearer. As your skin clears of acne, this medication will boost your happiness and confidence.