Contrast medium reactions correlated with time of day

Dynamic physiologic and psychological changes occur in patients awaiting excretory urography. A total of 2,000 patients were studied to see if rates of reaction to urographic contrast materials are influenced by the time of day such injections are given. Examinations performed between 7:00 A.M. and 2:00 P.M. were evaluated. The data suggest that reactions to radiographic contrast medium occur randomly and that a "safe" or "safer" time of day cannot be defined.