[Drug allergy in a population of surgical patients]

To determine the prevalence of drug allergies in a population of surgical patients. To establish a clinical classification of events as being very or not very likely to be allergic reactions. To detect which drug groups are associated with greater incidence of anaphylactic reaction and to analyze the severity of such reactions.

Epidemiological study. During a preoperative interview, patients were asked if they were aware of the existence of any episode of allergy to drugs. If a patient answered yes, a specific data collection questionnaire on allergies was completed. Based on signs and symptoms described by the patient, reactions were classified as indicating high likelihood of allergy, low likelihood of allergy, or as being of unknown origin.

We questioned 1,218 patients (754 women/464 men), of whom 159 (13.05%) reported being allergic to drugs. The total number of drugs employed was 212 (1.34 drugs/patient). Antibiotics (54.7%), nonsteroidal anti-inflammatory drugs (NSAIDs) (19.3%), radiological contrast media (6.1%) and local anesthetics (4.7%) were the substance groups most often mentioned. We classified 74.5% of the reactions as indicating high likelihood of allergy, 19.8% as indicating low likelihood, and 5.6% to be of unknown origin. The skin was involved in 72.1% of the reactions that were highly likely to have been caused by allergy; 6.9% of these reactions involved the respiratory tract, 4.4% the circulatory system, 12% the skin plus respiratory tract, and 4.4% the skin plus respiratory and circulatory systems. The most severe reactions (16.4%) were associated with radiological contrast media (36.4%), NSAIDs (33.3%) and intravenous administration (38.1%). Signs of latex allergy were seen in 0.4% and signs of allergy to hair dyes in 0.9%. All allergy tests were negative in all these patients.

Drug allergy is reported by 13% of patients. It is highly likely that 74.5% of reactions are due to allergy. Antibiotics are the most frequently implicated drugs, followed by NSAIDs. The most serious reactions are caused by radiological contrast media and NSAIDs. Intravenous administration causes the most serious reactions.