Chronic ITP therapy via a restricted access drug

COMPANY: GlaxoSmithKline

PHARMACOLOGIC CLASS: Thrombopoietin receptor agonist

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ACTIVE INGREDIENT: Eltrombopag (as olamine) 25mg, 50mg; tabs.

INDICATION: Thrombocytopenia due to chronic immune (idiopathic) thrombocytopenic purpura (ITP) in adults who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.

PHARMACOLOGY: Eltrombopag is an orally active thrombopoietin (TPO) receptor agonist that stimulates the proliferation and differentiation of megakaryocytes from bone marrow progenitor cells. It works by interacting with the thrombopoietin receptor to cause increased platelet production.

CLINICAL TRIALS: Two studies were conducted to evaluate the safety and efficacy of eltrombopag in treating chronic ITP. Patients who had completed at least one prior ITP therapy and who had a platelet count of <30×109/L were randomized to either eltrombopag or placebo daily for up to 6 weeks, then 6 weeks off therapy. The primary endpoint was the response rate, defined as a shift from baseline platelet count to >50 x 109/L at any time during treatment. The groups given eltrombopag 50mg/day had response rates of 59% and 70% in Studies 1 and 2, respectively; for those given placebo, the rates were 16% and 11%.

ADULTS:Take on empty stomach. Initially 50mg once daily. Moderate to severe hepatic impairment or East Asian ancestry: initially 25mg once daily. Titrate to maintain platelet count >50 x 109/L; max 75mg once daily. Adjust dose based on platelet count: see literature.

CHILDREN: Not recommended.

PRECAUTIONS: Monitor CBC, platelet count, and peripheral blood smears for cytopenias and abnormal morphologies; discontinue if no increase in platelet count occurs after 4 weeks at max dose, or if excessive increase in platelet count occurs (eg, >400 x 109/L), or if evidence of bone marrow fibrosis occurs (eg, cytopenias, nucleated RBCs). Monitor liver function closely before, during, and after treatment (see literature); discontinue if ALT >3 x ULN and is progressive or persistent for >4 weeks, or if it occurs with evidence of hepatic injury; reinitiation of therapy: not recommended; if restarted, use lower dose and monitor carefully. Do baseline eye exam; monitor for cataracts. Thromboembolism risk factors. Myelodysplastic syndromes. Renal impairment. Pregnancy (Cat.C). Nursing mothers: not recommended.

INTERACTIONS: Do not take within 4 hours of food/drugs containing polyvalent cations (eg, Fe+2, Ca+2, Al+2, Mg+2, Se+2, Zn+2). May potentiate substrates of organic anion transporter polypeptide 1B1 (eg, benzylpenicillin, most statins, methotrexate, nateglinide, repaglinide, rifampin); monitor and consider reducing their doses. May be potentiated by strong inhibitors of CYP1A2 (eg, ciprofloxacin, fluvoxamine) or CYP2C8 (eg, gemfibrozil, trimethoprim), and with moderate or strong inhibitors of UGT1A1 or UGT1A3.

ADVERSE REACTIONS: Nausea, vomiting, menorrhagia, myalgia, paresthesia, cataract, ecchymosis, thrombocytopenia, increased ALT/AST, conjunctival hemorrhage, increased risk of hematologic malignancies; thrombotic events with excessive increases in platelet counts; worsened thrombocytopenia after discontinuation.

NOTE: Physicians, pharmacies, and patients must enroll in Promacta Cares program. Register pregnant patients taking eltrombopag by calling (888) 825-5249.


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