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A. Celebrex labeling previously stated that a study performed in healthy volunteers showed that Celebrex did not change the anticoagulant effects of warfarin. However, the labeling also stated that caution should be used when administering Celebrex with warfarin, since these patients are at increased risk of bleeding complications.

The new labeling includes the above information, but also states that, subsequent to marketing, reports have been received of patients on warfarin who had increased anticoagulation and (in some cases) bleeding complications after treatment with Celebrex was started. The new labeling also cautions that when patients on warfarin start, or change, treatment with Celebrex, they should be monitored for any changes in the anticoagulant effect of the warfarin, particularly in the first few days.

Q. What prompted the change?

A. Post-marketing reports have been received describing patients on warfarin who had increased anticoagulation and (in some cases) bleeding complications after treatment with Celebrex was started.

Warfarin is an anticoagulant (popularly referred to as a "blood thinner"). Patients who are taking warfarin have an increased risk of bleeding complications. Starting or changing other medicines can sometimes change the anticoagulant effects of warfarin, and this can increase the risk of bleeding complications. Monitoring the level of anticoagulation in these patients, and adjusting medication doses if necessary to correct over- or under-coagulation, helps to minimize that risk.

Although clinical studies done prior to marketing of Celebrex did not show any significant effects of Celebrex on the anticoagulation effect of warfarin, the post-marketing reports indicate that it is possible for a significant effect to occur in some patients. Therefore, it became appropriate to include an explicit precaution to monitor for changes in the anticoagulant effect of warfarin soon after starting or changing Celebrex therapy.

Q. Should Celebrex be avoided in patients receiving warfarin or similar products?

A. Patients receiving warfarin can also receive Celebrex. Since Celebrex by itself does not affect platelet function or bleeding time, it can be an appropriate treatment option for patients taking warfarin, as long as the anticoagulation effect of warfarin is maintained at the proper level. To minimize any increased risk of bleeding, patients should be closely monitored (especially in the first few days) to see if any adjustment of their warfarin dosing is needed.

Q. What does this mean regarding the overall safety of Celebrex?

A. Patients receiving warfarin require monitoring of the level of anticoagulation produced by that drug. It is not unusual for them to need a change in warfarin dosage when there are changes in the other medicines they are receiving. Celebrex does not pose a unique or special risk in this regard, compared to other medicines that patients may receive. It is important, however, that patients who are receiving warfarin and then start taking Celebrex (or who have any other change in the other medicines that they are taking) be monitored for changes in the level of their anticoagulation, with adjustments in the dose of warfarin if necessary.

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