Ranitidine fails to suppress the growth in vitro of haemopoietic progenitors from human peripheral blood or bone marrow.

Ranitidine was added in various concentrations (25-1600 ng/ml) to clonal assays of haemopoietic progenitors of normal human peripheral blood or bone marrow. Although a significant reduction in colonies forming from granulocyte-macrophage progenitors (CFU-GM) was demonstrated at the lowest drug concentration, no significant growth suppression was seen at higher concentrations. There was no evidence for growth inhibition of either erythroid progenitors (BFU-E) or pluripotent progenitors (CFU-mix) at any of the drug concentrations studied. A direct toxic effect of ranitidine on normal haemopoietic progenitors thus appears an unlikely cause of cytopenias observed during treatment.