RESUMO
The use of ionic contrast media in radiologic examinations may cause a wide variety of anaphylactoid reactions. The aim of this double-blind randomized study was to determine whether a simple and inexpensive premedication based on an antihistamine could reduce the number of idiosyncratic reactions in 400 patients (251 men and 149 women) without a clinical history of allergy who were to receive an intravenous injection of a low-osmolality iodinated contrast medium. Twelve hours before examination, a group of 200 patients was given one 100-mg tablet of hydroxyzine; another group of 200 was given a placebo tablet under the same conditions. Results in the two groups were comparable at the .05 level of significance. Twenty-five patients in the placebo group had a reaction (mainly urticaria); only two patients in the hydroxyzine group had a reaction (P less than .0001; odds ratio, 14.1). No severe reaction occurred in either group. Because hydroxyzine and placebo were allocated at random, it is concluded that hydroxyzine reduces the frequency of minor anaphylactoid reactions in patients at low risk.
