Pharmacoepidemiology of warfarin use and deep venous thrombosis

Abstract

AbstractThree Southern California hospitals from the Center for Studies in Family Medicine research network participated in a study of the characteristics of patients using warfarin and of patients hospitalized with deep venous thrombosis. Computerized hospital and pharmacy data bases were searched to identify warfarin users and patients with deep venous thrombosis who received care between July 1987 and July 1990. Information on patients was abstracted from medical records.Of 337 warfarin users identified, 50% were male and the mean age was 51.6 years. The most common indications for warfarin therapy were cardiovascular conditions (45.8%) and deep venous thrombosis (31.8%). Warfarin therapy was initiated in the hospital for most patients (82%). Sensitivity to warfarin, as measured by the mean dose‐adjusted prothrombin time ratio, was 0.30. Female gender (p < 0.001) and increasing age (p = 0.03) were associated with increased sensitivity to warfarin (higher mean dose‐adjusted prothrombin time ratio). Regression analysis indicated that certain groups were significantly more sensitive to warfarin: females more than males (p < 0.0005); patients of other race/ethnicity more than blacks, hispanics, and whites (p < 0.05).Among the 114 patients hospitalized for deep venous thrombosis, there were 134 hospitalizations and 98 patients had only one hospitalization. Fifty‐eight per cent of the patients were male; the mean age was 44.2 years. The mean dose‐adjusted prothrombin time ratio was 0.28 for hospitalized patients.