Pharmacokinetics and pharmacodynamics of antimicrobial drugs in intensive care unit patients

Vancomycin Use in a Paediatric Intensive Care Unit of a Tertiary Care Hospital

BACKGROUND

Vancomycin is one of the commonly used anti-microbial drugs in intensive care units (ICUs). Guidelines recommend maintaining therapeutic trough levels of vancomycin (10-20 mg/L). The success of achieving the recommended therapeutic concentration of vancomycin is influenced by several factors, and this is even more complex in children, particularly those admitted in the ICU. Hence, we carried out the present study in children admitted in the ICU who were administered vancomycin.

METHODS

We carried out a chart review of children admitted in the paediatric ICU unit of a tertiary care hospital over a period of 3 years. Information on their demographic factors, diagnoses, duration of hospital stay, vancomycin treatment (dose, frequency and time of administration) and concomitant drugs, and vancomycin trough levels were retrieved. Descriptive statistics were used for representing the demographic factors, and multivariable logistic regression analyses were carried out to assess the determining factors.

RESULTS

One-hundred and two children were identified, of whom 13 had renal dysfunction. Two-hundred and fifty-two vancomycin trough levels were available, of which only 25% were observed in the recommended range (10-20 mg/L) amongst patients without any renal dysfunction and 22% amongst patients with renal dysfunction. Vancomycin was administered intravenously at an average [standard deviation (SD)] dose (mg/dose) of 13 (3.9) mostly either thrice or four times daily. Even in patients receiving vancomycin as a definitive therapy, only 40.9% achieved the recommended trough levels. Lower trough levels were associated with an increased risk of mortality. Nearly 4% of the levels were above 20 mg/L (toxic range). Seven children were suspected to have acute kidney injury (AKI) during the course of therapy where the cumulative vancomycin dose and mortality rate was higher. Only one serum vancomycin level during augmented renal clearance was observed in the recommended range. All the patients received at least one concomitant drug that either had nephrotoxic potential or predominant renal elimination, and use of a greater number of such drugs was associated with an increased risk of AKI.

CONCLUSION

The current vancomycin dosing strategy is ineffective in achieving therapeutic trough levels in children admitted to the ICU. Sub-therapeutic vancomycin trough levels significantly increase the risk of mortality.

Multiplex Therapeutic Drug Monitoring by Isotope-dilution HPLC-MS/MS of Antibiotics in Critical Illnesses

There is an ever-increasing demand for the therapeutic drug monitoring of antibiotics in many clinical facilities, particularly with regard to the implementation of hospital antibiotic stewardship programs. In the current work, we present a multiplex high-performance liquid chromatography-tandem mass spectrometry (HPCL-MS/MS) protocol for the quantification of cefepime, meropenem, ciprofloxacin, moxifloxacin, linezolid, and piperacillin, commonly used antibiotics in intensive care units. The method was previously comprehensively validated according to the guideline of the European Medicines Agency. After a rapid sample cleanup, the analytes are separated on a C8 reverse-phase HPLC column within 4 minutes and quantified with the corresponding stable isotope-labeled internal standards in electrospray ionization (ESI+) mass spectrometry in multiple reaction time monitoring (MRM). The presented method uses a simple instrumentation setting with uniform chromatographic conditions, allowing for the daily and robust antibiotic therapeutic drug monitoring in clinical laboratories. The calibration curve spans the pharmacokinetic concentration range, thereby including antibiotic amounts close to the minimal inhibitory concentration (MIC) of susceptible bacteria and peak concentrations (Cmax) that are obtained with bolus administration regimens. Without the necessity of the serum dilution before the sample cleanup, the area under the curve for an administered antibiotic can be obtained through multiple measurements.