Cimetidine suppression of CFU-C in males

A presumed cimetidine-induced granulocytopenia in a 6-year-old male with acute lymphocytic leukemia (ALL) prompted an investigation of the effects of cimetidine on in vitro bone marrow granulocyte colony growth (CFU-C) in normal individuals and ALL patients either on maintenance chemotherapy or off all therapy for at least 1 year. The addition of cimetidine resulted in a significant reduction of colony numbers as compared to untreated controls beginning at 1 x 10(-6) M (P less than 0.05) and increasing in significance as the concentration of cimetidine increased. Analysis of sex differences showed that CFU-C derived from females were not adversely affected by the addition of cimetidine (except at levels far in excess of recommended dosages) whereas CFU-C in males declined significantly from controls beginning at 1 x 10(-7) M (P less than 0.05) and became of greater significance as the concentration of cimetidine increased. These findings were identical for both normal individuals and ALL patients either receiving maintenance chemotherapy or off all therapy.