A placebo-controlled study of interaction between nabumetone and acenocoumarol

Aims The use of nonsteroidal anti-inflammatory drugs (NSAIDs) in patients t reated with oral anticoagulants is generally discouraged due to the risk of interactions that could increase the risk of bleeding complications. Avail able data suggest the NSAID, nabumetone, does not produce such an interacti on. We investigated whether nabumetone would interact with acenocoumarol, a n oral anticoagulant widely used in some European countries. Methods A double-blind, randomized, placebo-controlled study was conducted evaluating nabumetone (1-2 g daily for up to 4 weeks) in osteoarthritis pat ients with thromboembolic risk previously stabilized on acenocoumarol. The primary efficacy end point was the proportion of patients whose Internation al Normalized Ratio (INR) remained within established margins and whose ace nocoumarol dose was not changed. Fifty-six patients were randomized to rece ive nabumetone (n=27) or placebo (n=29). Results Eighteen patients in each group (67% for nabumetone and 62% for pla cebo) completed the study without showing INR or acenocoumarol dose changes , and were considered as study successes. Nine patients (33%) with nabumeto ne and 11 (38%) with placebo were considered study failures in the intentio n-to-treat analysis (one patient on nabumetone and four on placebo did not complete the study due to reasons not related to INR and acenocoumarol dose changes). No significant differences were found between groups with regard to study successes. There were two minor bleeding complications, one in ea ch group. Six patients per group presented with eight adverse experiences i n each group. Conclusions Treatment with nabumetone did not alter INR levels compared wit h placebo in patients stabilized on oral acenocoumarol who require NSAID th erapy. These results suggest that nabumetone does not produce a clinically relevant interaction with acenocoumarol. In orally anticoagulated patients without other associated risk factors, treatment with nabumetone for up to 4 weeks does not require increased monitoring of INR levels.