A drug used to treat thrombocytopenia (a lower-than-normal number of platelets in the blood) in patients with chronic immune thrombocytopenic purpura (a condition in which platelets are destroyed by the immune system). It is used in patients who did not get better with corticosteroids, immunoglobulins, or surgery to remove the spleen. It is also being studied in the treatment of other conditions and types of cancer. Promacta causes more platelets to be made in the bone marrow. It is a type of thrombopoietin receptor agonist. Also called eltrombopag olamine.