Potentiation of carmustine-cranial irradiation-induced myelosuppression by cimetidine.

In nine patients with glioblastomas, the histamine H2-receptor antagonist cimetidine was found to augment the myelosuppressive activities of carmustine and cranial irradiation. The nadir in neutrophil cell counts in this group averaged 650 +/- 220/microL. In a comparable series of 31 patients who did not receive cimetidine, the lowest neutrophil cell count averaged 2,160 +/0 240/microL. Further, marked suppression of these cells in the patients receiving cimetidine extended through day 42 of the treatment cycle. By contrast, the patients treated with carmustine and cranial irradiation alone did not experience significant neutropenia. This suggests that cimetidine may enhance the myelosuppressive effects of cytotoxic therapy.