Evaluation of a modified vancomycin nomogram for obese adults

Evaluation of a modified vancomycin nomogram for obese adults:

Abstract

Purpose

The purpose of this study was to compare therapeutic vancomycin trough levels in obese adults when using an original nomogram (phase I) versus a modified nomogram (phase II).

Methods

This study compared a vancomycin nomogram with a modified vancomycin nomogram for obese adults over 100 kg. The primary endpoint compared the percentage of sub-therapeutic, therapeutic, and supra-therapeutic vancomycin trough concentrations between the nomograms. Patients were included if they were at least 18 years of age, had a total body weight of 100–299 kg, and had an initial vancomycin trough level collected. Patients were excluded if they had end-stage renal disease or were on continuous renal replacement therapy.

Results

Therapeutic trough levels occurred in 85 out of 171 patients (50%) in phase I and 98 out of 149 patients (66%) in phase II. The incidence of both sub-therapeutic and supra-therapeutic troughs was less in phase II (p = 0.013). In the subgroup of adults aged 18 to 49 with a normalized creatinine clearance of greater than 90 mL/min, there was a trend in more therapeutic levels with the modified nomogram and less chance of sub-therapeutic levels (p = 0.088). In the subgroup of adults with a normalized creatinine clearance of 60–90 mL/min, there was significant improvement in therapeutic levels and a decrease in supra-therapeutic levels without increasing the percent of sub-therapeutic levels (p = 0.001).

Conclusion

The modified vancomycin nomogram at Cone Health showed significant improvement in therapeutic trough concentrations while reducing the rates of under and over dosing obese adults. The Cone Health–modified vancomycin nomogram could be a useful tool for initial dosing of vancomycin in the obese population.