Experience of romiplostin use in the management of ITP in a district general hospital setting-can fixed doses be used during stable phase to reduce wastage?

Abstract

The thrombopoetin receptor agonist, Romiplostim is indicated in chronic ITP patients with refractory ITP. We reviewed and analysed the data from two refractory ITP patients managed with Romiplostim. Using current manufacturer guidelines, we started with weekly dosing adjustments aiming for the recommended baseline platelet count of at least 50 9 109. Guidelines recommend an initiating dose of 1mcg/kg per week with increase in 1mcg increments to a maximum of 10 mcg/kg weekly until platelet count is stabilized above mentioned baseline. Hereafter, monthly blood tests are recommended and readjustment made if platelet count exceeds 200 x 109. Our patients commenced on 1mcg/kg, though once the platelet count was consistently above baseline, after a few dose adjustments, we found in both patients that during the stable phase, 250 mcg hence between 3 and 4 mcg/kg per patient respectively was an ideal maintenance dose that consistently kept the platelet count above 50 x 109 without requiring need for regular dose adjustment. Therefore these two patients have now been continued on this fixed dose and have shown an excellent response. Though our experience is limited, we have found a standard dose of 250 mcg to be an effective in maintenance of safe platelet counts. Also, as Romiplostim is available only in 250 and 500 mcg vials, variable doses will invariably lead to some wastage of this expensive drug. Given the economic climate and to simplify self-administration we propose further studies are required to assess whether a fixed dose of Romiplostim can be established for stable phase management of chronic ITP.