Continuous intravenous infusion of dipyridamole as adjunctive therapy in the treatment of thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is an uncommon hematologic thrombotic disorder characterized by fever, hemorrhagic and neurologic signs. The advent of plasma exchange has dramatically improved the prognosis of this disease, which was once inevitably fatal. However, mortality rates remain significant. Antiplatelet drugs have been widely used in combination with plasma exchange. In this pilot study we investigated the effects of an adjunctive therapy consisting of the continuous, intravenous infusion of dipyridamole, a modality of administration that has not been previously tested in this setting. Sixteen untreated TTP patients, diagnosed consecutively at our clinic, received daily plasma exchange together with intravenous methylprednisolone (1-2 mg/kg/twice daily) and a continuous i.v. infusion of dipyridamole (100 mg/day). A complete response was defined as an improvement in the platelet count to more than 150 x 10(9)/l for two consecutive days and no neurologic deterioration. The overall response rate was 87.5%. One patient failed to respond to the combination therapy but attained a consistent remission after autologous stem cells transplant. One patient was refractory to the combination therapy and died, after an initial but unsustained response. The results of this pilot study suggest that the continuous infusion of dipyridamole is safe and might provide additional benefit in the treatment of TTP when combined with plasma exchange and steroids. However, a randomized study will be necessary to properly test whether the addition of dipyridamole improves the efficacy of plasma exchange in patient with TTP.