Evaluation of a vancomycin dosing nomogram in achieving high target trough concentrations in Taiwanese patients

Background: The use of a vancomycin dosing nomogram is an alternative and more cost-effective method to conventional dosing; it reliably allows the achievement of trough vancomycin serum concentrations of 5-15. mg/l, with a successful clinical response. Recent guidelines have further recommended that the trough concentration be maintained at 15-20. mg/l for complicated infections. However, to date no published nomogram has been constructed to achieve the optimal trough of 15-20. mg/l in an Asian population. This study aimed to develop two vancomycin nomograms for the achievement of trough concentrations of 5-15. mg/l and 15-20. mg/l in the Taiwanese population, and to ensure the clinical efficacy and safety of such nomograms. Methods: The estimated concentrations and the real concentrations in our patient population were compared between six pharmacokinetic models to see which was the most precise. As the Ambrose method was the best at predicting the trough, this was used to create two nomograms, one for a target trough at 5-15. mg/l and the other for a target trough at 15-20. mg/l. We then evaluated the nomograms by analyzing the number of patients with the target vancomycin trough concentration, clinical and microbiological outcomes, and safety. Results: More patients who had dosing according to the nomogram had a vancomycin trough concentration within the desired target range than patients who had conventional dosing (65.1% vs. 32.1%, p = 0.001). These patients also had a higher rate of 'cure' as the clinical response (35.7% vs. 27.1%) and 'eradication' as the microbiological response (46.4% vs. 29.2%), and a lower rate of nephrotoxicity (14.3% vs. 22.9%). For the patients with a complicated infection, more had a trough between 15 and 20. mg/l when vancomycin was dosed with the nomogram than when dosed conventionally (41.2% vs. 12.1%, p = 0.019). Conclusions: We found that when dosing vancomycin with these nomograms, patients tended to have vancomycin trough concentrations within the target range and also to have a better outcome with regard to clinical efficacy and the safety profile.