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Risk of bleeding events is reduced among patients who report receiving instructions in warfarin use

Research Activities, March 2009, No. 343

Patients who report receiving instructions on how to take the anticlotting drug warfarin from a clinician and a pharmacist are much less likely to experience bleeding problems than patients treated by four or more physicians in a 3-month period or who fill warfarin prescriptions at several different pharmacies over the same period, a new study finds. Warfarin use is frequently involved in preventable serious adverse drug events, notably bleeding problems. The researchers suggest that warfarin patients who experience continuity of clinical and pharmacy care are less likely to be hospitalized for such problems.

In a 2-year study of elderly patients, the researchers identified 126 hospitalizations for internal bleeding related to taking warfarin among 2,370 patients. The risk of hospitalization due to a bleeding event was essentially the same for patients who were new users of warfarin or chronic users of the medication. The factors that were associated with the largest difference in risk of hospitalization were whether the patient received instructions on warfarin use from a doctor or nurse, and whether they received warfarin prescriptions from one doctor or at least four different doctors.

When other factors were taken into account, patients who said they received no medication instructions had more than twice the number of hospitalizations for bleeding events per 100 person-years of use than patients who reported receiving medication instructions from a doctor or nurse and a pharmacist. In addition, patients who filled prescriptions written by at least four different physicians over the last 3 months had nearly five times the hospitalizations per 100 person-years of warfarin use than patients whose prescriptions were all written by the same physician.

Finally, the researchers found that patients given written instructions or a combination of written and verbal instructions on taking the medication had less than half the risk of hospitalization than patients receiving no instructions. Verbal instructions alone did little to reduce the hospitalization risk.

The study was funded in part by the Agency for Healthcare Research and Quality (HS11530). More details are in "Patient reported receipt of medication instructions for warfarin is associated with reduced risk of serious bleeding events," by Joshua P. Metlay, M.D., Ph.D., Sean Hennessy, Pharm.D, Ph.D., A. Russell Localio, J.D., Ph.D., and others, in the October 2008 Journal of General Internal Medicine 23(10), pp. 1589-1594.

Current as of March 2009
Internet Citation: Risk of bleeding events is reduced among patients who report receiving instructions in warfarin use: Research Activities, March 2009, No. 343. March 2009. Agency for Healthcare Research and Quality, Rockville, MD.