Background Immune thrombocytopenia (ITP) is an autoimmune disease characterised by isolated thrombocytopenia (platelet count <100 000 mg/dL) due to both increased platelet destruction and low platelet production. Romiplostim is a thrombopoietin receptor agonist that increases platelet count and is used to treat adult chronic ITP patients who are refractory to other treatments. According to the labelling information, the recommended initial dose is 1 µg/kg once weekly. Subsequent doses are adjusted weekly in increments of 1 µg/kg to achieve and maintain a platelet count of ≥50x10⁹/L, without surpassing a maximum dose of 10 µg/kg. There are concerns that starting doses may be too low to obtain normalised platelet counts and decrease the risk of bleeding.

Purpose We aimed to describe dose escalation and time elapsed between dose levels during romiplostim treatment in ITP patients in clinical practice.

Material and methods A retrospective observational study was performed from January 2005 to September 2016. Adults ITP patients treated with romiplostim were included. Patient characteristics and romiplostim doses were obtained from the electronic prescription system. For each patient, time to next dose level was calculated. In those patients reaching the maximum dose, the time from initiation of therapy was also calculated.

Results 8 patients were included. 50% were men. Mean age was 50±15 years. Mean initial dose was 3.0±1.4 µg/kg. Only 2 patients started at 1 mg/kg. 88% of patients needed the maximum dose to attain a normalised platelet count. Median time on each dose level was 2 weeks (IQR 1–4). The time patients remained in the lower dose levels was much shorter than in the higher ones, as shown in the table.

Time elapsed from the beginning of treatment to the date the maximum dose level was reached was only 11 weeks (IQR=4.4–24.5).

Conclusion Most ITP patients receiving romiplostim start at doses higher than those recommended and go through a rapid dose escalation before reaching the dose that permits normalised platelet count. Most patients will require the maximum dose to achieve long term control of their disease.

No conflict of interest