These increase platelet production by stimulating the receptor for the hormone thrombopoietin (THPO). Romiplastin (Nplate™) is given by subcutaneous injection and Eltrombopag (Promacta®) is an oral agent. Both are licensed for the treatment of idiopathic thrombocytopenic purpura (ITP). Research is in progress to assess their ability to prevent bleeding and reduce platelet transfusions in aplastic anaemia, myelodysplasia and chemotherapy-induced thrombocytopenia. Early encouraging results are tempered by concerns about a possible increased risk of thromboembolic events, bone marrow fibrosis and a theoretical risk of stimulating malignant cells. Therefore, these agents should only be used off-label in the context of clinical trials.