cimetidine can modify the effects of whole body 'y-irradiation on ly mphohem atopoietic system

the hematopoietic syndrome is anticipated when a dose of radiation greater than 100 cgy is received. the resulting clinical situation is life-threatening because of opportunistic infections and gradual decline in immune competency due to irradiation. because of evidence of a possible immunomodulatory role for cimetidine, an antagonist of histamine h2 receptors, we studied the effects of this drug on radiationinduced lymphohematopoietic changes. the results obtained in this study indicate that cimetidine is effective in the reduction of radiation-induced injuries with a dose reduction factor of greater than 1.5. therefore, it might be useful as a radioprotector for low doses of radiation usually used for radiation therapy.