Divalproex and Thrombocytopenia

The use of valproate derivatives may be associated with dose-related thrombocytopenia, the incidence of which is generally low but has been reported at up to 27% in one study using high dosages (approximately 50 mg/kg/day of valproic acid). In that study, platelet counts returned to normal in all patients, some despite continued treatment. Valproate may also inhibit the secondary phase of platelet aggregation, although this effect is unlikely to be of clinical significance except during the concomitant use of other drugs that affect coagulation. However, altered bleeding time, ecchymosis, petechiae, bruising, hematoma formation, epistaxis, and frank hemorrhage have been reported rarely. Hypofibrinogenemia has also been observed. Therapy with valproate products, particularly at high dosages, should be administered cautiously in patients with significant active bleeding or a hemorrhagic diathesis, including hemostatic and/or coagulation defects associated with hemophilia, vitamin K deficiency, hypoprothrombinemia, thrombocytopenia, thrombocytopathy, or severe hepatic impairment. The manufacturers recommend platelet counts and coagulation tests prior to initiating therapy and at periodic intervals thereafter, as well as before planned surgery. The dosage should be reduced or the drug withdrawn if clinical evidence of hemorrhage, bruising, or a disorder of hemostasis or coagulation occurs.