Hypersensitivity reactions associated with 5-hydroxytryptamine3-receptor antagonists: a class effect?

Background The 5-hydroxytryptamine3 (5-HT3)-receptor antagonists, granisetron, ondansetron, and tropisetron are effective anti-emetic medications for use during chemotherapy for cancer and they are generally well tolerated. Their adverse event profiles broadly overlap and include headache and gastrointestinal symptoms, especially constipation. Hypersensitivity reactions have been reported very rarely. Methods We describe two patients who developed severe hypersensitivity reactions following exposure to a 5-HT3 receptor antagonist after having experienced mild to moderate hypersensitivity symptoms following previous exposure to a different 5-HT3 receptor antagonist. Findings A literature search on hypersensitivity reactions associated with these drugs suggests that these are the first reported instances of cross-reactive hypersensitivity. Interpretation There may be a drug class effect, and we caution against switching to another 5-HT3 receptor antagonist in patients who have suffered even mild hypersensitivity reactions during previous therapy with 5-HT3 receptor antagonist.