From the Research
Cross-reactivity between H2 blockers and H1 blockers in patients with hypersensitivity reactions to H2 blockers is generally uncommon, and patients can typically use H1 blockers safely, as evidenced by the most recent study 1. The chemical structures and mechanisms of action of H1 and H2 blockers are different, which supports the idea that cross-reactivity is unlikely. H1 blockers primarily target receptors in blood vessels and smooth muscle, while H2 blockers affect receptors in the stomach that regulate acid production. Some key points to consider:
- The most recent study 1 found no significant difference in the rates of hypersensitivity reactions in patients receiving paclitaxel with or without an H2 antagonist.
- Another study 2 reported two cases of H2-receptor antagonist-induced anaphylactic reactions, but did not find significant cross-reactivity with other H2-receptor antagonists.
- An older study 3 discussed the potential benefits of using H1 and H2 blockers in combination for allergic diseases, but did not address cross-reactivity directly.
- A study from 2016 4 evaluated the impact of premedications, including H1 and H2 blockers, on the incidence of carboplatin hypersensitivity reactions, but did not find a significant reduction in reactions with the addition of these blockers. In rare cases, some patients with multiple drug hypersensitivity syndrome might react to both classes of blockers. If a patient has experienced a severe reaction to an H2 blocker, it would be prudent to use the first dose of an H1 blocker under medical supervision. For patients with confirmed H2 blocker allergy who require acid suppression, proton pump inhibitors (like omeprazole or pantoprazole) are generally safe alternatives as they work through a completely different mechanism than histamine antagonists.