Comparison of three pretreatment protocols to prevent anaphylactoid reactions to radiocontrast media

Three pretreatment regimens were compared for prevention of anaphylactoid reactions in 149 patients who previously had reacted to radiocontrast media (RCM) administration. From 1976 to 1980, 52 patients were treated with 50 mg of oral prednisone 13, 7, and 1 hour before and 50 mg intramuscular diphenhydramine 1 hour before procedures (group I). From 1980 to 1984, 48 patients received 300 mg oral cimetidine one hour before procedure in addition to the other regimen (group II). From 1984 to 1989, 49 patients received the three drugs and 25 mg oral ephedrine one hour before procedures (group III). Previous reactions were similar in each group, consisting of urticaria and/or angioedema in all patients, hypotension in some (groups I, 5; II, 6; III, 4), and wheezing in two (group I). Readministration of RCM was intraarterial (groups I, 18; II, 20; III, 20) or intravenous. Generalized reactions upon readministration of RCM occurred in 4 (8%) of group I and 3 (6%) of both groups II and III. All reactions consisted of urticaria and/or angioedema, were mild, and required no specific treatment. In a separate group of ten patients whose previous reactions to RCM were life threatening (shock), pretreatment was accompanied by a provocative dosing regimen. Two patients (20%) experienced systemic reactions that resulted in termination of the procedure. All our pretreatment regimens were equally effective; however, we favor a more comprehensive pretreatment protocol (regimen III) based upon our lack of demonstrated adverse effects and a possible therapeutic advantage as reported by other investigators.(ABSTRACT TRUNCATED AT 250 WORDS)