Effects of cimetidine on haematopoiesis in vitro.

The possible modifications in haematopoiesis induced by cimetidine were studied in normal bone marrow cultures in vitro. When cimetidine was added in the therapeutic range, there was no significant change in either granulocytic-macrophagic (CFU-GM) or erythroid (BFU-E) colony growth. However, when cimetidine was added to the culture at 2 to 25 times the therapeutic range, a small but significant inhibition of both types of colony growth was found. We conclude that cimetidine in the therapeutic range does not induce inhibition of haematopoiesis in vitro but does in doses above the therapeutic range when inhibition is dose-dependent.