Prednisolone is a synthetic glucocorticoid, a derivative of cortisol, used to treat a variety of inflammatory and autoimmune conditions and some cancers. It is the active metabolite of the drug prednisone and is used especially in patients with liver failure, as these individuals are unable to metabolize prednisone into active prednisolone; it is primarily metabolized via the liver enzyme, 11-β-hydroxydehydrogenase. Adverse effects are not generally seen with short term therapy, but weight gain, impaired immune response, and behavioral disturbances commonly occur with longer durations of treatment. It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.