Population pharmacokinetics of amikacin in patients with pediatric cystic fibrosis

Anti-infectives in Pediatric Patients with Cystic Fibrosis: A Comprehensive Review of Population Pharmacokinetic Analyses

Pulmonary complications are the leading cause of morbidity and mortality in pediatric patients with cystic fibrosis. Altered pharmacokinetic parameters in this population, as well as high inter- and intra-individual variability, complicate the optimization of anti-infective treatments. In this review, we aim to summarize and describe all anti-infective population pharmacokinetic (popPK) models applied to pediatric populations with cystic fibrosis. Our objectives were to identify the most-reported structural models and retained covariates and to compare the dosing regimens used in clinical routine with those recommended in literature and guidelines. A literature search was done through the PubMed database from inception to August 2024. Studies were retained only if they complied with the inclusion and exclusion criteria. The review included 21 popPK models covering the pharmacokinetic profiles of eight different molecules. Among these, five are recommended antibiotics for treating pulmonary infections in patients with cystic fibrosis. All models incorporated body composition and/or renal function measures as covariates in their pharmacokinetic parameter equations. Standard dosing regimens in the studies were consistent with guidelines and literature recommendations. This is the first review summarizing and describing all anti-infective popPK models in pediatric patients with cystic fibrosis. Improved estimation of pharmacokinetic parameters and a clearer understanding of variability sources will enhance the optimization of antibiotic treatment in clinical practice. Finally, the impact of new targeted therapies on the management of this population will have to be closely monitored in the years ahead.

Comparative assessment of trough and peak levels and AUC24 for amikacin in nontuberculous mycobacterial infection

BACKGROUND

Amikacin, an aminoglycoside antibiotic, is widely used for the treatment of nontuberculous mycobacterial (NTM) infections. To date, therapeutic drug monitoring (TDM) of amikacin has primarily relied on the measurement of peak and trough levels as indicators rather than the 24-hr area under the concentration-time curve (AUC24).

METHODS

NTM patients referred for amikacin TDM from March 2021 to May 2023 were assessed for the AUC24 values based on administered dose. We investigated re-admission rates, all-cause mortality and AFB smear results to evaluate clinical outcome based on the actual AUC24 values. Ototoxicity and nephrotoxicity were also investigated as adverse effects in correlation with TDM parameters.

RESULTS

Among 65 patients, the mean and median values of AUC24 were 234 and 249 mg·hr/L, respectively. In a group of patients with AUC24 values less than 250 mg·hr/L, 42.4 % of patients were re-admitted for pulmonary symptoms. On the contrary, another group with AUC24 values equal to or more than 250 mg·hr/L, had lower re-admission rates (25.0 %). They also showed lower all-cause mortality rates and more improvement on acid-fast bacilli smear results. Moderate to poor correlation between AUC24 values and peak/trough levels were observed. Ototoxicity and nephrotoxicity were revealed to be associated with drug exposure duration rather than AUC24 values.

CONCLUSION

In this study, we performed comparative assessment of trough/peak level, traditional clinical marker for amikacin TDM, and AUC24 value. Although AUC24 values showed poor to moderate correlation to trough/peak levels, higher AUC24 correlated with favorable clinical outcomes without additional risk of toxicity.

Time-dependent pharmacodynamics of amikacin on Mycobacterium abscessus growth and resistance emergence

Mycobacterium abscessus pulmonary disease is increasing in prevalence globally, particularly for individuals with cystic fibrosis. These infections are challenging to treat due to a high rate of resistance. Amikacin is critical to treatment, but the development of toxicity, amikacin resistance, and treatment failure are significant challenges. Amikacin has been characterized previously as peak-dependent and extended-interval dosing is commonly used. In our hollow fiber infection model of M. abscessus, amikacin exhibited time-dependent rather than the expected peak-dependent pharmacodynamics. Humanized amikacin exposures with more frequent, short-interval dosing (continuous infusion or every 12 hours) yielded improved microbiological response compared to extended-interval dosing (every 24 hours or 1-3 times per week). Short-interval dosing inhibited growth with a mean (SD) maximum Δlog10 colony forming units of -4.06 (0.52), significantly more than extended-interval dosing (P = 0.0013) every 24 hours, -2.40 (0.58), or 1-3 times per week, -2.39 (0.38). Growth recovery, an indicator of resistance emergence, occurred at 6.56 (0.70) days with short-interval dosing but was significantly earlier with extended-interval dosing (P = 0.0032) every 24 hours, 3.88 (0.85) days, and 1-3 times per week, 3.27 (1.72) days. Microbiological response correlated best with the pharmacodynamic index of %T > minimum inhibitory concentration (MIC), with an EC80 for growth inhibition of ~40%T > MIC. We used a previously published population model of amikacin to determine the probability of achieving 40%T > MIC and show that current dosing strategies are far below this target, which may partially explain why treatment failure remains so high for these infections. These data support a cautious approach to infrequent amikacin dosing for the treatment of M. abscessus.IMPORTANCEPulmonary disease caused by Mycobacterium abscessus complex (MABSC) is increasing worldwide, particularly in patients with cystic fibrosis. MABSC is challenging to treat due to high levels of antibiotic resistance. Treatment requires 2-4 antibiotics over more than 12 months and has a significant risk of toxicity but still fails to eradicate infection in over 50% of patients with cystic fibrosis. Antibiotic dosing strategies have been largely informed by common bacteria such as Pseudomonas aeruginosa. The "pharmacodynamic" effects of amikacin, a backbone of MABSC treatment, were thought to be related to maximum "peak" drug concentration, leading to daily or three times weekly dosing. However, we found that amikacin MABSC kill and growth recovery, an indicator of antibiotic resistance, are dependent on how long amikacin concentrations are above the minimum inhibitory concentration, not how high the peak concentration is. Therefore, we recommend a re-evaluation of amikacin dosing to determine if increased frequency can improve efficacy.

Cystic fibrosis year in review 2019: Section 2 pulmonary disease and infections

During the year 2019, research and case reports or series in the field of cystic fibrosis (CF) were in abundance. To adequately address the large body of CF research published during 2019, the CF year in review will be divided into three sections. This report is the second section, focusing specifically on new research related to pulmonary disease and infections. Additional sections will concentrate on CF transmembrane conductance regulator modulators and the multisystem effects of CF. It is an exciting time to be providing care for patients and their families with CF with all the exciting new discoveries that will be shared in these reviews.

Evaluating the efficacy of inhaled amikacin as an adjunct to intravenous combination therapy (ceftazidime and amikacin) in pediatric cystic fibrosis pulmonary exacerbation

Background: Pseudomonas aeruginosa is the most common microorganism found in the sputum culture of Cystic fibrosis (CF) patients causing the pulmonary destruction. Aminoglycosides have a low diffuse rate from lipid membranes, and respiratory system secretions. Regarding the burden of pulmonary exacerbation caused by the pseudomonas aeruginosa in cystic fibrosis patients in the long term and the limited number of clinical trials focused on appropriate treatment strategies, the present study evaluated the concurrent inhaled and intravenous aminoglycoside antibiotics for pulmonary exacerbation caused by the pseudomonas aeruginosa as a safe and effective treatment in children. Method: This study was a blinded, randomized clinical trial phase conducted in a tertiary referral pediatric teaching hospital from May 2021 to May 2022. The patients were randomly allocated to receive intravenously administered ceftazidime and Amikacin alone or with inhaled Amikacin. Forced expiratory volume (FEV1), Amikacin via the level, kidney function tests, audiometry, inflammatory markers (erythrocyte sedimentation rate and C-reactive protein), hospital stay, and bacterial eradication rate were compared in two therapy groups. Results: the average FEV₁ has increased by 47% in Neb + group compared to Neb- group following treatment. Hospital stay was lower in Neb + group. No renal toxicity or ototoxicity was observed in both therapy groups. Pseudomonas aeruginosa eradication rate Neb- and Neb + groups were 44% and 69%, respectively (p-value = 0.15). Conclusion: Concurrent inhaled and intravenous Amikacin is safe and effective to treat Pseudomonas aeruginosa exacerbation in CF patients. Moreover, co-delivery antibiotics' route treatment increased the eradication rate. Although not statistically significant, never the less, it is clinically relevant. The intervention reduced the length of hospitalization in this group. Clinical Trial Registration: clinicaltrials.gov, identifier [IRCT20120415009475N10].

Defining the Importance of Age-Related Changes in Drug Clearance to Optimizing Aminoglycoside Dosing Regimens for Adult Patients with Cystic Fibrosis

BACKGROUND AND OBJECTIVE

The number of adults living with cystic fibrosis (CF) has increased and will continue to do so with the approval of cystic fibrosis transmembrane conductance regulator (CFTR) modulators. Because systemic aminoglycosides are commonly administered for CF pulmonary exacerbations, we sought to define optimized dosing regimens using a population pharmacokinetic modeling and simulation approach.

METHODS

Adult CF patients admitted for pulmonary exacerbation, receiving at least 72 h of systemic gentamicin, tobramycin, or amikacin, with measured concentrations were included. Covariates [e.g., age, weight, creatinine clearance (CRCL)] were screened. Population modeling was completed using Monolix, and simulations were conducted in R. Simulated exposures were calculated using noncompartmental analysis. Once-daily fixed (10 mg/kg) and exposure-matched dosing (i.e., 15, 10, 7.5, 6 mg/kg for ages 20, 30, 40, and 50 years, respectively) strategies were compared. First-24 h exposures were evaluated for each strategy according to the probability of target attainment (PTA) (ratio of peak plasma concentrations relative to the minimum inhibitory concentration [C_max/MIC] or ratio of the area under the concentration-time curve to MIC [AUC/MIC]) and the probability of toxic exposure (PTE) (trough concentration, C_trough > 2 mg/l).

RESULTS

Forty-eight adult patients (55% female) were included. A one-compartment model best fit the data. Estimates for volume of distribution (V) and clearance (CL) were 22 l and 5.57 l/h, respectively. Weight significantly modified CL and V. Age significantly modified CL and was more influential than CRCL. PTA was > 90% at MICs ≤ 1 mg/l for fixed doses of 10 mg/kg and for exposure-matched doses at MIC ≤ 1 mg/l. Exposure-matched dosing reduced PTE roughly 50% in patients aged 40 and 50 years vs. fixed dosing.

CONCLUSIONS

Exposure-matching maintained PTA at MICs ≤ 1 mg/l while reducing toxicity risk in older patients compared to fixed dosing. Confirmatory studies are needed.

A Population Pharmacokinetic Modeling Approach to Determine the Efficacy of Intravenous Amikacin in Children with Cystic Fibrosis

BACKGROUND

In children with cystic fibrosis (CF), the currently recommended amikacin dose ranges between 30 and 35 mg/kg/d; however, data supporting this dosing efficacy are lacking. In this article, the objectives were to develop a nonparametric pharmacokinetic population model for amikacin in children with CF and investigate the efficacy and toxicity at different dose rates for distinct minimum inhibitory concentration (MIC) clinical breakpoints using Monte Carlo simulations.

METHODS

Data from 94 children with CF (613 serum concentrations) from the Bordeaux University Hospital's CF-centre were analyzed. After determination of nonparametric pharmacokinetic population model parameters and associated influent covariates in Pmetrics, 1000 Monte Carlo simulations were performed for 7 different dose rates between 30 and 60 mg/kg/d, to predict the probability of obtaining peak serum amikacin ≥10 × MIC and trough level ≤2.5 mg/L, for MIC values between 1 and 16 mg/L.

RESULTS

The median (min-max) age and weight were 10 (0.3-17) years and 29 (6-71) kg, respectively, with only 2 children younger than 1 year of age. Body weight and creatinine clearance significantly impacted the amikacin volume of distribution and clearance. The mean relative bias/root mean squared error between observed and individual predicted concentrations was -0.68%/8.1%. Monte Carlo simulations showed that for sensitive bacteria with MICs ≤ 4, 30 mg/kg/d was most appropriate for a 100% success rate; for bacteria with MICs ≥ 8 [eg, Pseudomonas aeruginosa (MICamikacin = 8)], a dose of at least 40 mg/kg/d allowed a high success probability (90%), with a trough level below 2.5 mg/L.

CONCLUSIONS

For intermediate pathogens, a dose of at least 40 mg/kg/d can improve efficacy, with an acceptable calculated residual trough level in cases of normal or hyperfiltration. Because amikacin undergoes renal clearance, which is immature until 1 year of age, dosing recommendations for this age group may be markedly high, warranting cautious interpretation.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Drug Treatment of Non-Tuberculous Mycobacteria in Cystic Fibrosis

Non-tuberculous mycobacteria (NTM) are an emerging group of pulmonary infectious pathogens of increasing importance to the management of patients with cystic fibrosis (CF). NTM include slow-growing mycobacteria such as Mycobacterium avium complex (MAC) and rapidly growing mycobacteria such as Mycobacterium abscessus. The incidence of NTM in the CF population is increasing and infection contributes to significant morbidity to the patient and costs to the health system. Treating M. abscessus requires the combination of multiple costly antibiotics for months, with potentially significant toxicity associated with treatment. Although international guidelines for the treatment of NTM infection in CF are available, there are a lack of robust pharmacokinetic studies in CF patients to inform dosing and drug choice. This paper aims to outline the pharmacokinetic and pharmacodynamic factors informing the optimal treatment of NTM infections in CF.

Population Pharmacokinetics Analysis of Amikacin Initial Dosing Regimen in Elderly Patients

There are limited data of amikacin pharmacokinetics (PK) in the elderly population. Hence, we aimed to describe the population PK of amikacin in elderly patients (>70 years old) and to establish optimized initial dosing regimens. We simulated individual maximum concentrations in plasma (Cmax) and minimal concentrations (Cmin) for several dosing regimens (200–2000 mg every 24, 48, and 72 h) for patients with creatinine clearance (CCr) of 10–90 mL/min and analyzed efficacy (Cmax/minimal inhibitory concentration (MIC) ≥ 8) for MICs of 4, 8, and 16 mg/L and safety (Cmin < 4 mg/L). A one-compartment model best described the data. CCr was the only covariate associated with amikacin clearance. The population PK parameter estimates were 2.25 L/h for clearance and 18.0 L for volume of distribution. Dosing simulations recommended the dosing regimens (1800 mg) with dosing intervals ranging 48–72 h for patients with CCr of 40–90 mL/min based on achievement of both efficacy for the MIC of 8 mg/L and safety. None of the dosing regimens achieved the targets for an MIC of 16 mg/L. We recommend the initial dosing regimen using a nomogram based on CCr for an MIC of ≤8 mg/L in elderly patients with CCr of 40–90 mL/min.