Pharmacokinetic/Pharmacodynamic Analysis of Daptomycin Against Staphylococcus aureus and Enterococcus faecium in Pediatric Patients by Monte Carlo Simulation

Safety and Treatment Outcomes of Infants and Children Treated With Daptomycin: Six-Year Experience From a Pediatric Academic Medical Center

Daptomycin is a common treatment for serious infections caused by gram-positive bacteria in adult patients; however, data regarding its safety and efficacy in the pediatric population are limited. This was a retrospective chart review of adverse reactions and treatment outcomes associated with daptomycin use in children <13 years old who received at least 1 dose of daptomycin. At least 1 dose of daptomycin was received by 147 patients. Seventy-two patients received daptomycin for 5 or more days. New-onset loose stools on daptomycin initiation were reported for 14 (9.5%) patients, elevations in creatine kinase in 3 (2%) patients, and elevated aspartate transaminase and alanine transaminase in 13 (8.8%) and 9 (6.1%) patients, respectively. Two patients (1.4%) had daptomycin discontinued due to specific concerns for adverse drug reactions. Daptomycin was found to be safe and effective in this pediatric cohort that included young children and infants with a variety of types and severities of infections.

Daptomycin Dose Optimization in Pediatric Staphylococcus aureus Bacteremia: A Pharmacokinetic/Pharmacodynamic Investigation

Daptomycin is an antibiotic with Gram-positive activity, including methicillin-resistant Staphylococcus aureus, for which optimal pediatric dosing is unknown. This study aimed to evaluate daptomycin exposures achieved with package label dosing and to identify dosing regimens necessary to enhance efficacy and minimize toxicity in children with S. aureus bacteremia. Monte Carlo simulations were performed to determine probability of target attainment (PTA) for six pediatric age cohorts. Area under the curve to minimum inhibitory concentration ratio (AUC0-24:MIC) ≥666 was used to determine the PTA for efficacy (PTAE). Minimum concentration (Cmin) ≥24.3 mg/L determined the PTA for toxicity (PTAT). Acceptable dosing regimens were those which achieved the combined target of ≥90% PTAE and ≤5% PTAT. Package label dosing of daptomycin yielded insufficient efficacy with only 26.3% PTAE in children 13-24 months, 39.5% PTAE in children 2-6 years, 30.1% PTAE in children 7-11 years, and 50.1% PTAE in adolescents ≥12 years. To achieve the combined efficacy and safety target, doses of 18-24 mg/kg in children 3-12 months, 20-24 mg/kg in children 13-24 months, 19-24 mg/kg in children 2-6 years, 17-19 mg/kg in children 7-11 years, and 10-14 mg/kg in adolescents ≥12 years are necessary. Package label dosing resulted in suboptimal exposure for the majority of pediatric patients in all age groups evaluated. If targeting validated efficacy and safety endpoints, daily daptomycin doses of at least 20 mg/kg in children ≤6 years, 17 mg/kg in children 7-11 years, and 10 mg/kg in adolescents ≥12 years are necessary. Clinical studies evaluating these higher doses are needed.

Population Pharmacokinetic/Pharmacodynamic Modelling of Daptomycin for Schedule Optimization in Patients with Renal Impairment

The aims of this study are (i) to develop a population pharmacokinetic/pharmacodynamic model of daptomycin in patients with normal and impaired renal function, and (ii) to establish the optimal dose recommendation of daptomycin in clinical practice. Several structural PK models including linear and non-linear binding kinetics were evaluated. Monte Carlo simulations were conducted with a fixed combination of creatinine clearance (30-90 mL/min/1.73 m2) and body weight (50-100 kg). The final dataset included 46 patients and 157 daptomycin observations. A two-compartment model with first-order peripheral distribution and elimination kinetics assuming non-linear protein-binding kinetics was selected. The bactericidal effect for Gram+ strains with MIC ≤ 0.5 mg/L could be achieved with 5-12 mg/kg daily daptomycin based on body weight and renal function. The administration of 10-17 mg/kg q48 h daptomycin allows to achieve bactericidal effect for Gram+ strains with MIC ≤ 1 mg/L. Four PK samples were selected as the optimal sampling strategy for an accurate AUC estimation. A quantitative framework has served to characterize the non-linear binding kinetics of daptomycin in patients with normal and impaired renal function. The impact of different dosing regimens on the efficacy and safety outcomes of daptomycin treatment based on the unbound exposure of daptomycin and individual patient characteristics has been evaluated.

Physiologically based pharmacokinetic modeling of daptomycin dose optimization in pediatric patients with renal impairment

Background and Objective: Daptomycin is used to treat Gram-positive infections in adults and children and its dosing varies among different age groups. We focused on the pharmacokinetics of daptomycin in children with renal impairment, which has not been evaluated.

Methods: A physiologically based pharmacokinetic (PBPK) model of daptomycin was established and validated to simulate its disposition in healthy populations and adults with renal impairment, along with a daptomycin exposure simulated in pediatric patients with renal impairment.

Results: The simulated PBPK modeling results for various regimens of intravenously administered daptomycin were consistent with observed data according to the fold error below the threshold of 2. The Cmax and AUC of daptomycin did not differ significantly between children with mild-to-moderate renal impairment and healthy children. The AUC increased by an average of 1.55-fold and 1.85-fold in severe renal impairment and end-stage renal disease, respectively. The changes were more significant in younger children and could reach a more than 2-fold change. This scenario necessitates further daptomycin dose adjustments.

Conclusion: Dose adjustments take into account the efficacy and safety of the drug; however, the steady-state Cmin of daptomycin may be above 24.3 mg/L in a few instances. We recommend monitoring creatine phosphokinase more than once a week when using daptomycin in children with renal impairment.

Clinical Pharmacokinetics of Daptomycin

Due to the low level of resistance observed with daptomycin, this antibiotic has an important place in the treatment of severe Gram-positive infections. It is the first-in-class of the group of calcium-dependent, membrane-binding lipopeptides, and is a cyclic peptide constituted of 13 amino acids and an n-decanoyl fatty acid chain. The antibacterial action of daptomycin requires its complexation with calcium. Daptomycin is not absorbed from the gastrointestinal tract and needs to be administered parenterally. The distribution of daptomycin is limited (volume of distribution of 0.1 L/kg in healthy volunteers) due to its negative charge at physiological pH and its high binding to plasma proteins (about 90%). Its elimination is mainly renal, with about 50% of the dose excreted unchanged in the urine, justifying dosage adjustment for patients with renal insufficiency. The pharmacokinetics of daptomycin are altered under certain pathophysiological conditions, resulting in high interindividual variability. As a result, therapeutic drug monitoring of daptomycin may be of interest for certain patients, such as intensive care unit patients, patients with renal or hepatic insufficiency, dialysis patients, obese patients, or children. A target for the ratio of the area under the curve to the minimum inhibitory concentration > 666 is usually recommended for clinical efficacy, whereas in order to limit the risk of undesirable muscular effects the residual concentration should not exceed 24.3 mg/L.

Daptomycin in the treatment of enterococcal bloodstream infections and endocarditis: a EUCAST position paper

SCOPE

This position paper describes the view adopted by EUCAST on the role of daptomycin in the treatment of serious infections caused by Enterococcus species.

BACKGROUND

High-dose daptomycin is considered effective in the treatment of enterococcal bloodstream infection (BSI) and endocarditis, although published clinical experience with the latter condition is limited.

METHODS

EUCAST reviewed the available published data on pharmacokinetics-pharmacodynamics (PK-PD), resistance selection, clinical efficacy and safety for the use of 10-12 mg/kg/day of daptomycin for these conditions, noting that the doses licensed by the European Medicines Agency are only 4-6 mg/kg/day, and only for infections caused by Staphylococcus aureus.

FINDINGS AND RECOMMENDATIONS

The PK-PD evidence shows that, even with doses of 10-12 mg/kg/day, it is not possible to treat infections caused by isolates at the upper end of the wild-type distributions of Enterococcus faecalis (with MICs of 4 mg/L) and E. faecium (with MICs of 4 or 8 mg/L). For this reason, and because there are ongoing issues with the reliability of laboratory testing, EUCAST lists daptomycin breakpoints for Enterococcus species as "IE"-insufficient evidence. EUCAST advises increased vigilance in the use of high-dose of daptomycin to treat enterococcal BSI and endocarditis. Additional PK-PD studies and prospective efficacy and safety studies of serious Enterococcal infections treated with high-dose daptomycin may permit the setting of breakpoints in the future.