Morphological alterations in blood and bone marrow of ribavirin-treated monkeys.

The antiviral drug ribavirin (1, beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) produced significant hematologic effects when administered to rhesus monkeys by intramuscular injection over 10 days in doses of 30 or 100 mg/kg/day. The monkeys developed dose-related progressive anemia and thrombocytosis associated with marrow erythroid hypoplasia and megakaryocyte hyperplasia. In addition, bone marrow examination revealed phagocytosis of erythroid elements by histiocytes; vacuolization of erythroid precursors, and to a lesser extent precursors of other cell types; and occasional erythroid precursors with megaloblastoid appearance. The alterations were transient and disappeared on discontinuation of the drug.