Objective: To investigate the clinical features of immediate hypersensitivity induced H2 antagonists and their cross reactivity.
Methods: We retrospectively evaluated clinical characteristics of patients diagnosed as immediate hypersensitivity to H2 antagonists at 4 University hospitals in Busan, Korea and analyzed the data from skin test to various H2 antagonists.
Results: A total of 12 patients were enrolled in this study. The mean age was 48 ± 4 years (rage 26-68) and 6 patients were female. Most common culprit drug was ranitidine (N=10, 83%) followed by cimetidine (N=1) and nizatidine (N=1). Half of patients had previously allergic reaction to H2 antagonists but were not diagnosed before. The mean latent time was 42.09 + 18.4 minutes (range, immediate~210). Anaphylaxis was the most common symptom (N=7, 58%), followed by local urticaria (N=3, 25%), and systemic urticaria (N=2, 17%). All patients except one had positive reactions in skin test (9 in prick test, 2 in intra-dermal test). All of the cross-reactions were between ranitidine, famotidine, and cimetidine. One patient had positive reaction to all histamine H2 antagonists.
Conclusion: Histamine H2 antagonists are widely used and generally tolerated. However, anaphylaxis was the most common symptom in histamine H2 antagonists induced immediate hypersensitivity and ranitidine was the most common causative drug. In addition, our data showed significant cross reactivity between drugs.