Eltrombopag is a thrombopoietin (TPO) nonpeptide mimetic administered orally that activates the TPO receptor by binding to the transmembrane domain and initiates signaling cascades that induce proliferation and differentiation of megakaryocytes from bone marrow progenitor cells. Eltrombopag under brand name promacta is approved for the treatment of the low blood platelet counts in adults with chronic immune (idiopathic) thrombocytopenia (ITP), when certain other medicines, or surgery to remove the spleen, have not worked well enough. ITP is a condition that may cause unusual bruising or bleeding due to an abnormally low number of platelets in the blood. Eltrombopag has also been approved for the treatment of thrombocytopenia (low blood platelet counts) in patients with chronic hepatitis C to allow them to initiate and maintain interferon-based therapy and to treat patients with severe aplastic anemia who have had an insufficient response to immunosuppressive therapy.