A graphic nomogram for warfarin dosage adjustment.

We assessed the ability of a graphic nomogram to adjust steady-state warfarin dosages and to predict international normalized ratios (INR) after a dosage change, compared with an anticoagulation clinic pharmacist and a Bayesian regression computer program. Study subjects were 108 men and 3 women receiving warfarin anticoagulation. In all patients the median absolute errors in predicted INR values for the nomogram, computer program, and pharmacist were 0.33, 0.46, and 0.48, respectively. The nomogram was significantly more precise than both other methods (p=0.036). In a subset of 50 patients who required dosage reductions, the median absolute INR prediction errors for the nomogram, computer program, and pharmacist were 0.35, 0.54, and 0.48 respectively. The nomogram was significantly more precise than the pharmacist (p=0.005) and computer (p=0.002). The ability to provide more precise dosage reductions of warfarin may be of clinical importance in light of current recommendations for higher-intensity warfarin therapy and maintenance of higher INR values. Prospective validation of the performance of this nomogram in a routine clinical setting is warranted.

Comparison of three methods for cyclosporine area under the curve monitoring calculations.

A method of therapeutic monitoring of cyclosporine by using area under the curve (AUC) has been previously proposed. However, different mathematical methods of calculating AUC may produce different results. We compared three methods of calculating whole blood 12-h AUC of cyclosporine A (CsA) at steady state in 16 pediatric renal allograft recipients. The linear trapezoidal method tended to significantly overestimate AUC when compared with a method combining linear and log trapezoidal methods, or the Lagrange technique combined with the logarithmic trapezoidal method, producing mean differences of 13.8 ng*h/ml [95% confidence interval (CI), 7.3-20.3] and 12.8 ng*h/ml [95% CI, 7.3-18.3], respectively. However, these differences appear to be of little clinical significance because they comprised < 1% of the calculated AUC value. The calculated AUCs by the three methods produced values with similar means and overlapping 95% CI. These data suggest that use of any of these three mathematical methods, when used to calculate CsA AUC for the determination of average steady-state concentrations and dose rate calculations, will produce similar results.