Objective: To evaluate the effects of pharmaceutical care on patients with a mechanical prosthetic valve. Three outcomes were measured including therapeutic INR, complications and patient’s knowledge.

Materials and methods: This was a prospective descriptive study to determine outcomes of pharma- ceutical care on patients who underwent heart valve surgery between January and December 2009 at Songklanagarind hospital. Patients were individually counseled on warfarin therapy. Drug related problems (DRPs) were identified and resolved. The outcomes measured on INR, complications and patient’s knowledge. The score of the patient’s knowledge was compared from the first visit to the second visit. Data were analyzed by descriptive statistics, paired-t-test and McNemar chi-square.

Results: Thirty-four patients were recruited. Within the first 3 months after surgery, the proportion of patients who achieved stable therapeutic INR was 35%. Incidence of bleeding included 12 events in 7 patients with 2 patients experiencing major bleeding (5.88%). The major DRPs was found non- compliance (34%). However, the data also showed that 81% of physicians responded to pharmacist’s interventions. Patient’s knowledge score regarding warfarin therapy significantly increased after receiving the counseling service (3.82±3.55, 7.88±1.95; p<0.001).

Conclusion: Pharmaceutical care on patients with a mechanical prosthetic valve could improve patient’s knowledge of warfarin therapy. However, in order to achieve INR goal and prevent complications, patient care management should be continuously revised by multidisciplinary team.