Objective: Cross-sensitivity between aspirin and acetaminophen in aspirin-sensitive asthmatic patients has been reported with frequencies ranging from 0% to 29%. The relationship is dose-dependent for acetaminophen challenges, ranging between 300 and 100 mg.
Methods: To determine the prevalence of cross-sensitivity to high-dose acetaminophen, we performed single-blind acetaminophen oral challenges with 1000 mg and 1500 mg in 50 aspirin-sensitive asthmatic patients and in 20 non-aspirin-sensitive asthmatic control subjects.
Results: Overall, 17 of 50 (34%) of aspirin-sensitive asthmatic patients reacted to acetaminophen in doses of 1000 to 1500 mg (95% confidence interval: 20% to 49%). By contrast, none of the 20 non-aspirin-sensitive asthmatic patients reacted to acetaminophen (95% confidence interval: 0% to 14%). This difference was highly significant (p = 0.0013), supporting the hypothesis that cross-sensitivity between aspirin and acetaminophen is unique in aspirin-sensitive asthmatic patients.
Conclusion: Although high-dose ( > 1000 mg) acetaminophen cross-reactions with aspirin were significant with respect to frequency (34%), such reactions included easily reversed bronchospasm in only 22%, and were generally mild. We recommended that high doses of acetaminophen (1000 mg or greater) should be avoided in aspirin-sensitive asthmatic patients.