Betamethasone is a steroid medication. It is used for a number of diseases including rheumatic disorders such as rheumatoid arthritis and systemic lupus erythematosus, skin diseases such as dermatitis and psoriasis, allergic conditions such as asthma and angioedema, preterm labor to speed the development of the baby, Crohn disease, cancers such as leukemia, and along with fludrocortisone for adrenocortical insufficiency, among others. It can be taken by mouth, injected into a muscle, or applied as a cream. When given by injection, anti-inflammatory effects begin in around two hours and last for seven days. Serious side effects include an increased risk of infection, muscle weakness, severe allergic reactions, and psychosis. Long term use may cause adrenal insufficiency. Stopping the medication suddenly following long term use may be dangerous. The cream commonly results in increased hair growth and skin irritation. Betamethasone belongs to the glucocorticoid class of medication. Betamethasone was approved for medical use in the United States in 1961. The cream is on the World Health Organization's List of Essential Medicines, the most important medication needed in a basic health system. It is available as a generic medication. In the United States the pills and injectable solution are expensive while the cream is not.