Oral Anticoagulants

Cost-Justification of a Clinical Pharmacist-Managed Anticoagulation Clinic

A cost-benefit evaluation of a clinical pharmacistmanaged anticoagulation clinic (AC) was performed. Outpatient and hospital records were examined for 26 patients in the treatment group with an AC clinic and 26 patients in the control group. Therapeutic prothrombin times were maintained within the treatment group to a significantly greater extent than within the control group (p < 0.001).

The AC was successful in preventing hospitalizations resulting from hemorrhage or thromboembolism (p < 0.01). The abnormal prothrombin times on admission in the control group correlated with hemorrhagic and thromboembolic admissions (p < 0.05, p < 0.005, respectively).

Patients were hospitalized 3.22 days and .048 days per patient-treatment-year in the control and treatment groups, respectively. The net savings in reduced hospitalization costs per year in the treatment group was $211776. The benefit:cost ratio (B:C) was 6.55, suggesting the program is socially valuable.

This clinical pharmacist-managed AC was effective in maintaining therapeutic prothrombin times, and reducing the incidence of hospitalizations resulting from anticoagulation complications, and can be cost-justified based on a cost-benefit analysis.

Effect of warfarin on plasma concentrations of vitamin K dependent coagulation factors in patients with stable control and monitored compliance

There is a discrepancy in the results of reported studies of levels of vitamin K dependent coagulation factors in patients on warfarin therapy. This may have arisen partly because of the problem of assuring compliance with therapy in outpatients. The plasma concentrations of the vitamin K dependent clotting factors II, VII, IX and X were studied in 23 outpatients whose adherence to prescribed warfarin therapy was determined using a pharmacological indicator of compliance. In these patients, who were shown to have consistently good compliance and stable anticoagulant control over a period of 3-6 months, the activities in plasma of the four coagulation factors were not equally suppressed. Factor IX levels were significantly greater than those of factor VII (P less than 0.0001) which in turn were significantly greater than the levels of factor II (P less than 0.0001) or factor X (P less than 0.0001). There was no significant difference between the levels of factors II and X which were depressed to a similar extent. The proportion of variability of the International Normalized Ratio (INR) explained by linear regression was 51-77% and a model was derived to predict the INR from the mean of the levels of the four clotting factors. The concentrations of the coagulation factors II, VII, IX and X are likely to be highly dependent on the degree of compliance with warfarin therapy which should be taken into account when investigating the behaviour of these factors.

Factor II, VII, IX and X concentrations in patients receiving long term warfarin

Using standard one stage clotting assays the concentrations of factors II, VII, IX and X were determined in 37 patients stabilised on warfarin for between three months and 17 years. Contrary to popular belief, the concentrations were not equally depressed, with factor X the lowest, factor II at intermediate value, factors VII and IX the highest. Some 71% of the variance of the British corrected ratio (BCR) could be accounted for by measurement of the factors assayed. Analysis of this variance showed 91% of the explained variance attributable to factor II, 7% to factor VII, 1.6% to factor IX and 0.4% to factor X. With the sudden and recent withdrawal of human thromboplastin, investigation of the sensitivities of the animal thromboplastins to changes in vitamin K dependent factors in orally anticoagulated patients is needed to ensure that the potentially alarming falls in factors II and X in these patients are being adequately detected.

Cost-justification of a clinical pharmacist-managed anticoagulation clinic

A cost-benefit evaluation of a clinical pharmacist-managed anticoagulation clinic (AC) was performed. Outpatient and hospital records were examined for 26 patients in the treatment group with an AC clinic and 26 patients in the control group. Therapeutic prothrombin times were maintained within the treatment group to a significantly greater extent than within the control group (p less than 0.001). The AC was successful in preventing hospitalizations resulting from hemorrhage or thromboembolism (p less than 0.01). The abnormal prothrombin times on admission in the control group correlated with hemorrhagic and thromboembolic admissions (p less than 0.05, p less than 0.005, respectively). Patients were hospitalized 3.22 days and .048 days per patient-treatment-year in the control and treatment groups, respectively. The net savings in reduced hospitalization costs per year in the treatment group was $211776. The benefit:cost ratio (B:C) was 6.55, suggesting the program is socially valuable. This clinical pharmacist-managed AC was effective in maintaining therapeutic prothrombin times, and reducing the incidence of hospitalization resulting from anticoagulation complications, and can be cost-justified based on a cost-benefit analysis.