Prevention of anaphylactoid reactions after radiographic contrast media infusion by combined histamine H1- and H2-receptor antagonists: results of a prospective controlled trial.

In a prospective randomized trial, 800 patients undergoing intravenous urography were pretreated with either intravenous prednisolone (group I), the H1-antagonist clemastine (group II), a combination of clemastine and the H2-antagonist cimetidine (group III) or 0.9% saline (group IV). There was an overall incidence of 18 - 19% side reactions, when subjective and objective symptoms were regarded together. There was no significant difference between the four groups in the total incidence. The same applies when considering subjective side effects including the symptom 'heat sensation' that occurred in 10 - 12% of all patients. However, when side effects excluding the symptom 'heat sensation' were regarded and the individual groups were compared, there was a significant difference in frequency between the control group (12%) and the combined H1/H2 group (6%). Prednisolone and clemastine did not produce a significant reduction of side effects. The combined application of histamine H1- and H2-antagonists might be useful in prophylaxis of radiographic contrast media-induced adverse reactions.