Single-dose and Steady-state Pharmacokinetics of Vancomycin in Critically Ill Patients Admitted to Medical Intensive Care Unit of India

A study to explore the appropriateness of dosing regimen of vancomycin in critically ill patients in a tertiary care unit of India

Introduction

Vancomycin is used in proven or suspected MRSA and MRE infections. An AUC/MIC ratio of ≥400 is the current accepted critical PK/PD"efficacy" target of vancomycin activity. The present study was conducted to ascertain the appropriateness of practice of current dosage regimen of vancomycin (1 g BD) based on population pharmacokinetic approach.

Methods

A single-center prospective study with the ICU setting of a tertiary care center was conducted. A total of 15 adult patients with sepsis treated with vancomycin were included over 15 months from May 2019 to July 2020. Blood samples were obtained at 5, 10, and 30 minutes and thereafter at 2 and 6 hours following the completion of the vancomycin infusion. The data obtained from HPLC estimation was analyzed using a population pharmacokinetic approach with NLME, Phoenix 8.3.2.166. The pharmacokinetic model was based on covariates such as bodyweight and urinary creatinine clearance to predict drug concentrations.

Results

A total of 83 vancomycin blood samples were analyzed. The mean AUC_0-last and AUC_0-∞ in patients who improved and died were (AUC_(0-last)=293 (152.97); AUC_(0-∞)=535.14 (353.67) and (AUC_(0-last)=137.19 (51.37); AUC_(0-∞)=582.12 (1036.09) respectively, the difference between the two outcome groups was not statistically significant (p=0.104). The pharmacokinetic model was best described by a two-compartment linear model. The goodness-of-fit plots showed that the final covariate pharmacokinetic model (having bodyweight and urinary creatinine clearance) adequately described the observed vancomycin concentrations.

Conclusions

Based on the finding of the study it was concluded that 1 g BD dosing of vancomycin is inappropriate. Including covariates such as urinary creatinine clearance and weight in the pharmacokinetic model helped predict drug concentrations more accurately. However, further studies are required to demonstrate efficacy regarding applying this strategy.

Therapeutic Drug Monitoring of Vancomycin in Jordanian Patients. Development of Physiologically-Based Pharmacokinetic (PBPK) Model and Validation of Class II Drugs of Salivary Excretion Classification System (SECS)

Vancomycin is a commonly used antibiotic for multi-drug resistant gram-positive infections treatment, especially methicillin-resistant Staphylococcus aureus (MRSA). Despite that, it has wide individual pharmacokinetic variability and nephrotoxic effect. Vancomycin trough concentrations for 57 Jordanian patients were measured in plasma and saliva through immunoassay and liquid chromatography-mass spectrometry (LC-MS/MS), respectively. Plasma levels were within accepted normal range, with exception of 6 patients who showed trough levels of more than 20 μg/ml and vancomycin was discontinued. Bayesian dose-optimizing software was used for patient-specific pharmacokinetics prediction and AUC/MIC calculation. Physiological-based pharmacokinetic (PBPK) vancomycin model was built and validated through GastroPlus™ 9.8 using in-house plasma data. A weak correlation coefficient of 0.2478 (P=0.1049) was found between plasma and saliva concentrations. The suggested normal saliva trough range of vancomycin is 0.01906 to 0.028589 (μg/ml). Analysis of variance showed significant statistical effects of creatinine clearance and albumin concentration on dose-normalized Cmin plasma and saliva levels respectively, which is in agreement with PBPKmodeling. It can be concluded that saliva is not a suitable matrix for TDM of vancomycin. Trough levels in plasma matrix should always be monitored for the safety of patients.