Extended-Interval Dosing of Aminoglycoside Antibiotics in Critically Ill Patients

Recommendations of Gentamicin Dose Based on Different Pharmacokinetic/Pharmacodynamic Targets for Intensive Care Adult Patients: A Redefining Approach

Background

In addition to the maximum plasma concentration (C_max) to the minimum inhibitory concentration (MIC) ratio, the 24-hour area under the concentration-time curve (AUC_24h) to MIC has recently been suggested as pharmacokinetic/pharmacodynamic (PK/PD) targets for efficacy and safety in once-daily dosing of gentamicin (ODDG) in critically ill patients.

Purpose

This study aimed to predict the optimal effective dose and risk of nephrotoxicity for gentamicin in critically ill patients for two different PK/PD targets within the first 3 days of infection.

Methods

The gathered pharmacokinetic and demographic data in critically ill patients from 21 previously published studies were used to build a one-compartment pharmacokinetic model. The Monte Carlo Simulation (MCS) method was conducted with the use of gentamicin once-daily dosing ranging from 5-10 mg/kg. The percentage target attainment (PTA) for efficacy, C_max/MIC ~8-10 and AUC_24h/MIC ≥110 targets, were studied. The AUC_24h >700 mg⋅h/L and C_min >2 mg/L were used to predict the risk of nephrotoxicity.

Results

Gentamicin 7 mg/kg/day could achieve both efficacy targets for more than 90% when the MIC was <0.5 mg/L. When the MIC increased to 1 mg/L, gentamicin 8 mg/kg/day could reach the PK/PD and safety targets. However, for pathogens with MIC ≥2 mg/L, no studied gentamicin doses were sufficient to reach the efficacy target. The risk of nephrotoxicity using AUC_24h >700 mg⋅h/L was small, but the risk was greater when applying a C_min target >2 mg/L.

Conclusion

Considering both targets of Cmax/MIC ~8-10 and AUC_24h/MIC ≥110, an initial gentamicin dose of 8 mg/kg/day should be recommended in critically ill patients for pathogens with MIC of ≤1 mg/L. Clinical validation of our results is essential.

Antimicrobial resistance: factors and outcomes

Antimicrobial resistance in the ICU is characterized by increasing overall resistance rates among gram-negative and gram-positive pathogens and increased frequency of multidrug-resistant organisms. In addition to basic principles of appropriate drug selection for empiric and definitive therapy, other specific strategies that may decrease problems of resistance through improved use of antimicrobials include appropriate application of pharmacokinetic and pharmacodynamic principles to antimicrobial use, aggressive dosing of antimicrobials, use of broad-spectrum and combination antimicrobial therapy for initial treatment, decreased duration of antimicrobial therapy, hospital formulary-based antimicrobial restrictions, use of antimicrobial protocols and guidelines, programs for restriction of target antimicrobials, scheduled antimicrobial rotation, and use of antimicrobial management programs. Combinations of various approaches may offer the best potential for effectively intervening in and reducing the spread of resistant pathogens in critically ill patients.