Inhibition of platelet production induced by an antiplatelet drug, anagrelide, in normal volunteers.

Administration of anagrelide, an antiplatelet agent, to ten normal male subjects was accompanied by an asymptomatic fall in platelet count. The drop was gradual and usually occurred within two weeks. Only a slight shortening of platelet survival was seen. Bone marrow morphology appeared normal. Measurement of platelet production rates showed a reduced response to thrombocytopenia. A substantial increase in the percentage of large platelets was observed in drug treated subjects. These observations are compatible with a selective inhibition of platelet production. Based upon these findings, the use of anagrelide will probably be best limited to short-term applications or to conditions where selective lowering of platelet count may be desired such as in polycythemia rubra vera or idiopathic thrombocytosis.