Grant: Operating Grant

Warfarin is the most widely prescribed blood thinner medication for the treatment and prevention of blood clots. Its use, however, is greatly complicated by the drug's narrow therapeutic dose range and by the extensive variation in safe doses among different individuals to avoid exposing patients to clots formation or to bleeding events. Recent studies showed that two genes, together with environmental factors, can explain some of the variability between patients. New blood thinner medications are being developed that could eventually provide an alternative to warfarin treatment. In order to identify patients who are most likely to be exposed to serious bleeding or clot formation we propose to evaluate the genetic and clinical determinants of adverse responses to warfarin treatment. These include: (i) severe and potentially fatal bleeding, the most serious adverse response; (ii) major complications related to clot formation; and (iii) fluctuations in the International Normalised Ratio (INR), a parameter used to monitor warfarin treatment in order to establish the safe therapeutic dosage for each patient. This study will recruit 2,500 patients initiating warfarin therapy over a 2-year period. Patients will be selected from the warfarin clinics of 4 greater-Montreal area. They will be followed-up for 1 year as part of this research project. The prediction of adverse events in warfarin therapy is expected to allow a better management of treatment with blood thinner medications. This effort offers great potential for the improvement of personal and public health.