Hydroxyurea for treatment of polycythemia secondary to right-to-left shunting patent ductus arteriosus in 4 dogs.

Four adult dogs with polycythemia secondary to reversed patent ductus arteriosus (rPDA) were treated with hydroxyurea, a myelosuppressive agent, for 6-22 months. Regardless of initial hematocrit, clinical signs attributed to the presence of polycythemia improved with hydroxyurea treatment. Chronic hydroxyurea therapy (40-50 mg/kg PO q48h) was well tolerated in this group of animals; mild, clinically silent thrombocytopenia and leukopenia were detected in some animals but resolved with decreased dosage or dose frequency. Chronic hydroxyurea therapy may provide an alternative to repeated phlebotomy for therapy of polycythemia secondary to rPDA.