Isotretinoin is an anti-acne medication that is chemically related to retinoic acid and retinol (Vitamin A). Although its exact mode of action is unknown, this agent works by inhibiting sebaceous gland functioning, which diminishes oil production in the skin and hinders acne development. Isotretinoin is sold in many countries throughout the world, and is largely regarded as one of the most effective medications for treating severe acne.