OBJECTIVES: To compare the effectiveness of pharmacists and physicians in obtaining therapeutic anticoagulation on initiation of warfarin sodium therapy immediately following prosthetic cardiac valve insertion. Secondary objectives were the percentage of days with an international normalized ratio (INR) greater than four, the percentage of days with an INR less than two, the time to stabilize the INR within the therapeutic range, and the percentage of patients experiencing at least one major bleed. METHODS: This study was a before and after comparison using a retrospective chart review of patients who received warfarin sodium following cardiac valve surgery. Physicians dosed independently and pharmacists used a warfarin sodium nomogram to manage patients. RESULTS: A total of 227 patients (physician group, n=130; pharmacist group, n=97) satisfied the inclusion criteria. No differences were found between the two groups in the percentage of days in the therapeutic range (P=0.27), the percentage of days with INR less than two (P=0.06), the percentage of patients discharged before their INR stabilized (P=0.91) or the percentage of patients with a major bleed (P=0.72). The pharmacist group had 5.9% fewer days (P<0.001) with an INR greater than four than the physician group. CONCLUSIONS: Appropriately trained pharmacists appear equally safe and effective as physicians when managing warfarin sodium therapy in patients who have undergone cardiac valve replacement.