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How long does it take for Promacta to work?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Nov 14, 2023.

Official answer


Promacta (eltrombopag olamine) is a thrombopoietin receptor agonist that is used to increase low blood platelet counts (thrombocytopenia) in certain people with chronic immune thrombocytopenia (ITP) and severe aplastic anemia. Platelets are blood cells that help to form clots and stop bleeding.

How quickly does Promacta work in ITP and severe aplastic anemia?

Uses Time to work
To treat thrombocytopenia in people with ITP who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
  • Increases in platelet counts were detectable 1 week after starting treatment with Promacta in trials (Studies 773B and 773A) conducted in adults with chronic immune thrombocytopenia.

    A maximum response was seen after 2 weeks of therapy.
  • An initial response during the first 2 weeks of treatment was observed in 62% of the 26 pediatric patients who responded to treatment with Promacta - achieved a platelet response (≥ 50 x 109/L without rescue) for 6 out of 8 weeks (between weeks 5 and 12) of the Petit2 trial.
Thrombocytopenia with hepatitis C
To treat thrombocytopenia in patients with chronic hepatitis C to allow the initiation and maintenance of interferon-based therapy.
  • Two weeks was the median time to achieve the target platelet count of ≥ 90 x 109/L in patients enrolled in the Enable 1 and 2 trials. A total of 95% of the patients were able to receive antiviral therapy after treatment with Promacta.
Aplastic anemia combination therapy
In combination with standard immunosuppressive therapy for the first-line treatment of severe aplastic anemia.
  • It is unclear exactly how quickly Promacta + combination immunosuppressive therapy works in previously untreated patients with severe aplastic anemia. However, 87% (95% CI 75-100) of patients treated with Promacta once daily for the first 6 months of their treatment plan (cohort 3 Study US01T) had either a complete or partial response to Promacta + combination immunosuppressive therapy at 3 months.
  • A total of 24 of the 25 pediatric patients in cohort 3 also had a complete or partial response at 6 months, which was a key outcome measured by the trial.
Severe aplastic anemia
To treat patients with severe aplastic anemia who have had insufficient response to immunosuppressive therapy.
  • It is unclear exactly how quickly Promacta works in patients with severe aplastic anemia who have not responded to previous immunosuppressive therapy. However, 44% (11 of 25) of patients had at least some hematologic response to therapy at 12 weeks, with 9 of the 11 patients no longer needing platelet transfusions at that time.


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