Reduced antithrombin III levels during L-asparaginase therapy.

Antithrombin III levels were measured in serum before, during, and after therapy with three different dosage regimens of L-asparaginase in 11 children with acute lymphoblastic leukemia. Levels determined by both functional and immunologic methods were transiently reduced during alternate-day or daily L-asparaginase treatment but not affected when the drug was administered only every 10 days. The probable mechanism of this effect is impaired hepatic synthesis of antithrombin III, resembling the acute and transient deficiency of other asparagine-rich proteins during L-asparaginase administration.