Hi, Tretiva contains isotretinoin which belongs to a group of medicines known as retinoids are closely related to vitamin A derivative. It is used to treat severe acne by reducing the production of sebum that hasn t responded to other treatments. This kills acne causing bacteria and prevents pimples from appearing. It usually takes a few weeks to have a noticeable effect so keep taking it according to your doctor s advice. It has been observed in many patients that a single course of treatment effectively cures the condition and prevents it from coming back. Side effects if Tretiva are dry skin, nosebleed, vision problems, headache, back pain, joint pain, muscle pain, stuffy nose, sneezing, sore throat, increased liver enzymes, hair loss, sweating, ringing in the ear, dizziness, diarrhoea, heartburn, stomach pain, bloody stools, allergic reactions etc. Take care. Hope I have answered your questions. Let me know if I can assist you further. Regards, Dr. Zubayer Alam, General And Family Physician