Dose-response studies of the suppression of whole blood histamine and basophil counts by prednisone.

If some clinical problems (e.g., radiographic contrast media reactions) arise from mediator release by circulating basophils, prednisone's capacity to prevent such is likely to be at least partly related to its suppressive effects on whole blood histamine and basophil levels. To establish an optimal dosage schedule, 15 healthy male volunteers entered a two-phased study to determine (1) the single dose of prednisone required to produce maximal suppression of histamine and basophil levels and (2) the effects of repeated prednisone doses. Parameters monitored were whole blood histamine, quantitative basophil counts, white blood cell (WBC) and differential counts, and plasma prednisone, prednisolone, and cortisol levels. Fifty milligrams prednisone suppressed whole blood histamine levels as much as a larger dose and also showed a marked effect on circulating basophils and other leukocytes. Three 50-mg prednisone doses given at 6-hr intervals had a greater effect on whole blood histamine and circulating leukocytes than fewer doses. Thus, the commonly used empirical prednisone dosage regimen is supported. One implication of the results of this study is that greater suppression of blood basophils and histamine levels might be obtained by administering the last prednisone dose about 6 hr before procedures in which a very rapid release of mediators from basophils is anticipated.