Prophylactic antihistamines in the management of radiographic contrast reactions

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Abstract
Patients (220), referred for i.v. pyelography were assessed for adverse reactions. The effect of prophylactic antihistamines was evaluated. Patients were divided randomly into control, saline or chlorpheniramine-treated groups. Changes in serum total hemolytic complement (CH50) and immune complexes (IC) at 0, 1, 5, 10 and 20 min after injection of radiocontrast material were assayed. Of the 220 patients, 42 suffered reactions, classified clinically into allergic and nonallergic types. There was no difference in the incidence of allergic reactions between control and saline groups. Significantly less (P < 0.05) allergic reactions were noted in the antihistamine pretreatment group. Depressed CH50 occurred in 43 of 88 patients tested and persisted for at least 20 min in 22. There was no correlation between CH50 depressions and clinical symptoms. The IC remained unchanged throughout. Prophylactic antihistamines may diminish the incidence of allergic reactions. Complement activation occurred in a large number of patients, unrelated to symptomatology and did not appear to be the only factor responsible for adverse reactions.