ParaSustain tablets is a controlled release tablet with 665mg of Paracetamol. The active ingredient, paracetamol, is a commonly used pain killer/analgesic. It is also used for fever. How paracetamol works is still not completely understood but it is believed to act centrally in the brain. Each tablet contains 665 mg of paracetamol, specially formulated to give a sustained release profile of the medicine. Each dose should provide up to 8 hours of pain relief.