Background Idiopathic Thrombocytopenic Purpura (ITP) is a haemorrhagic disorder well known about its condition of having an abnormally low platelet count in blood. Romiplostim is a new thrombopoietin agent that stimulates the thrombopoietin receptors increasing the production of platelet.

Purpose The objective is to assess the effectiveness and safety of romiplostism in two paediatric patients with ITP and bad response to previous treatments, through off-label use. Some previous studies seem to support this indication, despite the limited experience of use.

Materials and methods Two patients of 8 and 12 years old are studied. They are diagnosed with chronic ITP and they didn't respond favourably to previous treatments (glucocorticoids in high doses and INTRAVENOUS immunoglobulins). The first of them was also splenectomised since 2009. Off-label use is applied in both cases before treatment starting, because technical specifications don't include the paediatric population. The evaluation of its effectiveness has been done by monitoring the patients through electronic medical history (patient platelet re-count, clinical situation and bleeding) for a period of 16 and 10 months respectively. The objective was to obtain a platelet count between 50-200 10⁹ / litre. The safety is measured through the study of the adverse side effects and the tolerance.

Results Before the treatment with romiplostism, patient 1 had the thrombocytopaenia for 7 years and the average platelet count was less than 50 10⁹ / litre. In patient 2 the previous values were 13 months and less than 40 10⁹ / litre, respectively. The initial dose, in both cases, was of 1 mcg/kg q1w and it was increased depending on the platelet count, being 4,5 mcg/kg q1w and 6,5 mcg/kg q1w the actual maintenance dose. The average platelet count achieved with these doses were 161 10⁹ / litre and 96 10⁹ / litre, respectively. Both patients have suffered some isolated decreases in their platelet counts, below the wanted values, this occurred until the ideal dose was found to achieve the desired levels though. Nevertheless, the clinical situation was favourable, with an improvement of the quality of life, such as psychological and physical conditions (neither hematomas nor epistaxis were present), during the studied period. The drug was well tolerated and without evidence of any adverse side effects.

Conclusions Romiplostism has shown as an effective option for the maintenance of the platelet count in comparison to previous treatments. Although a longer monitoring period is required to establish the optimal doses, it seems a well tolerated medication. Additional studies and long term monitoring of the possible side effects (reticulin formation in the bone marrow and malignant risks) are required, especially in specially in paediatrics. The authors shouldn't forget that this medicament has an elevated economic impact and a careful selection of the patient candidates should be done to be treated with it.