Improved outcomes in patients with acute allergic syndromes who are treated with combined H-1 and H-2 antagonists

Study objective: Although the addition of H-2 blockers to H-1 antagonists h as been promoted for use in anaphylaxis, there have been no large studies e stablishing the advantage of this approach in treating acute allergic syndr omes. In this study we tested the hypothesis that combined H-1 and H-2 bloc kage results in improved outcomes in patients treated for acute allergic sy ndromes compared with treatment with H-1 blockade alone. Methods: In a randomized, double-blind, placebo-controlled trial, 91 adult patients with acute allergic syndromes were treated with either 50 mg of di phenhydramine and saline solution (control group) or with 50 mg of diphenhy dramine and 50 mg of ranitidine (active group). These patients were treated with parenteral administration. Patients were recruited from an emergency department at an urban academic medical center. The primary endpoints were resolution of urticaria, angioedema, or erythema at 2 hours after protocol treatment. Areas of cutaneous involvement, heart rates, blood pressures, re spiratory findings, and symptom scores were also assessed at baseline, 1 ho ur, and 2 hours. Results: There were significantly more patients without urticaria at 2 hour s among the patients in the active group compared with those in the control group. Both groups had similar proportions of urticaria at baseline. Logis tic regression models to predict resolution of urticaria, which accounted f or baseline urticarial involvement, showed odds ratios in favor of the acti ve group treatment. Similar findings were observed when the absence of boil 1 urticaria and angioedema was considered as the dependent variable. There was not a significant difference between the 2 groups with regard to the a bsence of erythema or angioedema (irrespective of the presence of urticaria ) at 2 hours. Blood pressure and symptoms did not show differences between the 2 groups over time. Lower heart rates were observed 1 hour after treatm ent in the active treatment group (mean reduction 10 beats/min) compared wi th those found in the placebo group (mean reduction 6 beats/min). Conclusion: These data show that adding H-2 blockers to H-1 antagonists res ults in additional improvement of certain cutaneous outcomes for patients p resenting with acute allergic syndromes. These findings favor the recommend ation for using combined H-1 and H-2 antihistamines in acute allergic syndr omes.