A placebo-controlled study of interaction between nabumetone and acenocoumarol

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) in patients treated with oral anticoagulants is generally discouraged due to the risk of interactions that could increase the risk of bleeding complications. Available data suggest the NSAID, nabumetone, does not produce such an interaction. We investigated whether nabumetone would interact with acenocoumarol, an oral anticoagulant widely used in some European countries.

A double-blind, randomized, placebo-controlled study was conducted evaluating nabumetone (1-2 g daily for up to 4 weeks) in osteoarthritis patients with thromboembolic risk previously stabilized on acenocoumarol. The primary efficacy end point was the proportion of patients whose International Normalized Ratio (INR) remained within established margins and whose acenocoumarol dose was not changed. Fifty-six patients were randomized to receive nabumetone (n=27) or placebo (n=29).

Eighteen patients in each group (67% for nabumetone and 62% for placebo) completed the study without showing INR or acenocoumarol dose changes, and were considered as study successes. Nine patients (33%) with nabumetone and 11 (38%) with placebo were considered study failures in the intention-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 each group. Six patients per group presented with eight adverse experiences in each group.

Treatment with nabumetone did not alter INR levels compared with placebo in patients stabilized on oral acenocoumarol who require NSAID therapy. 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.