Population Study of Aminoglycoside Pharmacokinetics at a Hospital in South Carolina

Abstract

Objectives: To determine the pharmacokinetic parameters of a patient population from drug concentration measurements records created by the pharmacokinetic service at a regional hospital in South Carolina, to predict peak and trough concentrations from three large dose-extended interval (LDEI) protocols to determine which method produce the highest percentage of concentrations that fall in the desired ranges, and to compare pharmacokinetic parameters of overweight and normal weight patients. Methods: This was a descriptive, retrospective study that used clinical data from 121 of 208 patient data forms. The collected data included patient age, gender, weight, height, serum creatinine (Scr), measured serum peak and trough concentrations, time of dosing, dose and dosing interval. These were used to determine individual pharmacokinetic parameters and predict peak and trough concentrations from three LDEI dosing protocols. Results: Method II produced the highest percentage of patients with peaks and troughs falling into the target range (95.9%). The Hartford method produced the highest percentage (79.3%) of patients achieving peak concentrations >20mg/L. All three methods achieved low troughs of <2mg/L, <1mg/L, <0.5mg/L, and <0.1mg/L at least 95%, 80%, 70%, and 50% of the time, respectively. No statistical significance was found between the group having actual body weight/ideal body weight ratio (ABW/IBW) greater than 1.2 and another group having ABW/IBW <1.2 for ABW, volume of distribution (V), elimination half-life (T1/2) and aminoglycoside clearance (Clag). Also, when overweight patients were excluded, a higher correlation between elimination rate constant (k) and creatinine clearance (CrCl) was found than when all patients were combined. In other words, as k increases, CrCl increases. Implications: Even though Method II produced the greatest percentage of peak and trough concentrations within its stated target range, the Hartford method may be the best dosing protocol to use since it achieves high peak concentrations (>20mg/L) while maintaining low trough concentrations. In addition, based on our data, we can assume that overweight people affect the predicted k value. There was no statistical significance between actual and predicted pharmacokinetic characteristics in overweight patients.