Double-blind, randomized, parallel, placebo-controlled study of ibuprofen effects on thromboxane B₂ concentrations in aspirin-treated healthy adult volunteers

Background: Patients taking aspirin for cardioprotection may occasionally take over-the-counter (OTC) ibuprofen for pain relief, which might interfere with the antiplatelet effects of aspirin. Objective: The present study was undertaken to determine whether ibuprofen, taken according to OTC label directions, would affect inhibition of thromboxane B₂ (TXB ₂), a surrogate for platelet inhibition. Methods: This was a prospective, multiple-dose,single-center, double-blind, randomized, parallel, placebo-controlled study. Eligible subjects received chewable, immediate-release aspirin 81 mg QD for 8 days, and were then randomized to receive either ibuprofen 400 mg TID or placebo TID, in addition to aspirin, for 10 days. Results: Fifty-one subjects were randomized; 47(24 placebo, 23 ibuprofen) completed the study. No subjects withdrew prematurely. Subjects were predominantly white (49%) or black (38%), and 53% were male. The mean (SD) age was 38.4 (9.8) years and mean (SD) body weight was 173.2 (26.7) pounds. On days 1, 3, 7, and 10 of the study period, mean TXB₂ inhibitions were 99.24%, 98.88%, 97.75%, and 98.17% for ibuprofen and 98.82%, 98.93%, 98.75%, and 98.83% for placebo. Although a statistically significant reduction of TXBZ inhibition was seen in the ibuprofen group at days 7 and 10 (P = 0.003 and P = 0.023, respectively), TXB₂ inhibition was >90% on all days tested in all subjects. Aspirin, ibuprofen, and placebo were all well tolerated. There were 3 adverse events (1 mild and 2 moderate) during the aspirin run-in period and 8 (2 mild and 6 moderate) during the randomized study period. Conclusions: No clinically meaningful loss of cardioprotection was found, as reflected by TXB₂ inhibition in healthy volunteers who received OTC doses of ibuprofen. When using this regimen of OTC ibuprofen with immediate-release, low-dose aspirin, concerns about the loss of cardioprotective antiplatelet effects of aspirin are not supported by this study.