Dose Of Amikacin Research Articles

Evaluation of Amikacin Pharmacokinetics and Pharmacodynamics for Optimal Initial Dosing Regimen.

Amikacin has been one of the important antimicrobial agents against Gram-negative pathogens. However, there is discrepancy regarding the amikacin initial dosage, with some reports recently recommending ≥25 mg/kg and others the conventional dosage (15–20 mg/kg). Hence, we evaluated the optimal initial dosing regimen of amikacin. Pharmacokinetic (PK) parameters were estimated using a population PK analysis. The pharmacodynamic (PD) target was a ratio of ≥8 between the concentration achieved 1 h after beginning the infusion (C peak) and the minimal inhibitory concentration (MIC) of the liable bacteria. Based on the population PK parameters, we simulated individual C peak for several dosing regimens by Monte Carlo method and analyzed the C peak/MIC ratio for MICs from 0.5 to 32 μg/mL. This study included 35 infected patients (25 males), with a median (range) age and body weight of 70 (15–95) years and 49.5 (32.5–78) kg, respectively. A two-compartment model was used, and total body clearance (CL) significantly correlated with creatinine clearance, and volume of distribution (V d) with body weight. Regarding the probability to achieve a C peak/MIC of ≥8, the 15 mg/kg regimen was sufficient to achieve the PK/PD target in ≥90% of patients for a MIC of 4 μg/mL or less. The cumulative fraction of response in Pseudomonas aeruginosa was that 76% of patients achieved a C peak/MIC of 8 with the amikacin dosage of 15 mg/kg/day. We suggest that the 15-mg/kg once-daily dosage of amikacin be recommended as the initial dosage. As its maintenance dosage, the 15 mg/kg/day amikacin dosage is needed for a MIC of ≤4 μg/mL, and amikacin monotherapy for a MIC of ≥8 μg/mL should be avoided.

Addition of Ceftriaxone and Amikacin to a Ciprofloxacin plus Metronidazole Regimen for Preventing Infectious Complications of Transrectal Ultrasound-Guided Prostate Biopsy: A Randomized Controlled Trial.

Background. The objective of this study was to evaluate the efficacy of adding single doses of ceftriaxone and amikacin to a ciprofloxacin plus metronidazole regimen on the reduction of infectious complications following transrectal ultrasound-guided prostate biopsy (TRUS Bx). Materials and Methods. Four hundred and fifty patients who were candidates for TRUS Bx were divided into two groups of 225 each. The control group received ciprofloxacin 500 mg orally every 12 hours together with metronidazole 500 mg orally every 8 hours from the day prior to the procedure until the fifth postoperative day. In the second group, single doses of ceftriaxone 1 g by intravenous infusion and amikacin 5 mg/kg intramuscularly were administered 30–60 minutes before TRUS Bx in addition to the oral antimicrobials described for group 1. The incidence of infection was compared between the groups. Results. The incidence of infectious complications in the intervention group was significantly lower than that in the control group (4.6% versus 0.9%, p = 0.017). Conclusion. The addition of single doses of intramuscular amikacin and intravenously infused ceftriaxone to our prophylactic regimen of ciprofloxacin plus metronidazole resulted in a statistically significant reduction of infectious complications following TRUS Bx.

Comparison of Amikacin Pharmacokinetics in Neonates Following Implementation of a New Dosage Protocol.

The primary aim was to compare attainment of goal serum amikacin concentrations using two dosage regimens in patients admitted to a neonatal intensive care unit. Secondary objectives included comparison of percentages of supratherapeutic trough concentrations, and subtherapeutic and supratherapeutic peak concentrations. This was an Institutional Review Board-approved, retrospective study of neonates receiving amikacin during January-December 2013 (group 1) and January-December 2014 (group 2). Group 1 received amikacin dosage consistent with published recommendations, whereas group 2 was dosed using a modified protocol that was based on postmenstrual and postnatal age. Goal serum amikacin peak concentration was defined as 20 to 35 mg/L; hence, subtherapeutic and supratherapeutic peak concentrations were defined as <20 mg/L and >35 mg/L, respectively. Supratherapeutic trough concentrations were >8 mg/L. Between-group analysis was performed using Wilcoxon-Mann-Whitney test, Student t-test or χ2, or Fisher exact analysis as appropriate with a p value <0.05. A total of 278 neonates were included (group 1: n = 144; group 2: n = 134). Most patients were male (60%) and were admitted for prematurity or respiratory distress (77%). The median gestational age in group 1 was 34.4 weeks (range, 30.0-37.9 weeks) versus group 2 at 36.9 weeks (range, 31.4-38.9 weeks), whereas the postnatal age was similar between both groups at 4 days. There was a significant increase in attaining goal peak amikacin concentrations between groups 1 and 2, 34% versus 84%, p < 0.001, and decrease in supratherapeutic peak concentrations, 65% versus 12%, p < 0.001. There was no significant difference in subtherapeutic peak or supratherapeutic trough concentrations. A modified neonatal amikacin dosage protocol resulted in increased peak amikacin serum concentration compared with published dosage recommendations. Future research should focus on determination of the optimal dosage regimen in neonates.

Population Pharmacokinetic Characteristics of Amikacin in Suspected Cases of Neonatal Sepsis in a Low-Resource African Setting: A Prospective Nonrandomized Single-Site Study

BackgroundAmikacin exhibits marked pharmacokinetic (PK) variability and is commonly used in combination with other drugs in the treatment of neonatal sepsis. There is a paucity of amikacin PK information in neonates from low-resource settings. ObjectivesTo determine the PK parameters of amikacin, and explore the influence of selected covariates, including coadministration with aminophylline, on amikacin disposition in neonates of African origin. MethodsNeonates with suspected sepsis admitted to an intensive care unit in Accra, Ghana, and treated with amikacin (15 mg/kg loading followed by 7.5 mg/kg every 12 hours), were recruited. Serum amikacin concentration was measured at specified times after treatment initiation and analyzed using a population PK modeling approach. ResultsA total of 419 serum concentrations were available for 247 neonates. Mean (SD) trough amikacin concentration (from samples collected 30 minutes before the fourth dose) among term (n = 25), and preterm (<37 weeks’ gestation n = 36) neonates were 6.2 (3.4) and 9.2 (5.7) µg/mL, respectively (P = 0.02). A 1-compartment model best fitted amikacin disposition, and birth weight was the most important predictor of amikacin clearance (CL) and distribution (V). The population CL and V of amikacin were related as CL (L/h) = 0.153 (birth weight/2.5)1.31, V (L) = 2.94 (birth weight/2.5)1.18. There was a high between-subject variability (58.9% and 50.7%) in CL and V, respectively. CL and V were 0.058 L/h/kg and 1.15 L/kg, respectively, for a mean birth weight of 2.1 kg, and the mean half-life (based on 1-compartment model), was 13.7 hours. ConclusionsThe V and half-life of amikacin in this cohort varied from that reported in non-African populations, and the high trough and low peak amikacin concentrations in both term and preterm neonates suggest strategies to optimize amikacin dosing are required in this population.

Impact of a high loading dose of amikacin in patients with severe sepsis or septic shock.

BackgroundThe therapeutic effect of aminoglycosides is highest and optimal when the peak plasma concentration (C max)/minimal inhibitory concentration (MIC) ratio is between 8 and 10. The French guidelines recommend to use high doses of aminoglycosides for empiric antibiotic therapy in patients suffering from severe sepsis or septic shock. In clinical practice, the recommended target is an amikacin C max between 60 and 80 mg/L, which corresponds to approximately 8 times the MIC breakpoint, as defined by the European Committee on Antimicrobial Susceptibility Testing. The aim of this study was to assess the incidence and impact on mortality of an amikacin concentration between 60 and 80 mg/L in patients suffering from severe sepsis or septic shock.MethodsThis was a prospective observational cohort study conducted in two intensive care units (ICU). Patients receiving amikacin at a loading dose of 30 mg/kg for severe sepsis or septic shock were enrolled in the cohort. The target C max for amikacin was between 60 and 80 mg/L, as recommended by French guidelines (i.e. C max/MIC breakpoint = 8–10).ResultsOver the study period, the amikacin C max was <60 mg/L, between 60 and 80 mg/L, and >80 mg/L in 20 (18.2%), 46 (41.8%) and 44 (40%) of the 110 selected patients, respectively. Mortality rate was 40, 28.3 and 56.8% in the groups of patients with C max < 60 mg/L, 60 mg/L < C max < 80 mg/L and C max > 80 mg/L, respectively. Following multivariate analysis, mortality rate was significantly lower in the group of patients with amikacin C max between 60 and 80 mg/L than in the group of patients with amikacin C max > 80 mg/L (P = 0.004). The multivariate analysis also revealed that the factors independently associated with a higher in-ICU mortality rate were age (P = 0.02) and norepinephrine dose (P = 0.0001).Conclusions With a loading dose of 30 mg/kg of amikacin, concentration was potentially suboptimal (C max < 60 mg/L) in only 18.2% of patients. The pharmacodynamic target (60 mg/L < C max < 80 mg/L) recommended by French guidelines was reached in 41.8% of patients and was associated with reduced in-ICU mortality. But amikacin overexposure (i.e. C max > 80 mg/L) was frequent and potentially associated with increased mortality.

Effect of Dose on Intra-Articular Amikacin Sulfate Concentrations Following Intravenous Regional Limb Perfusion in Horses.

To compare synovial concentrations of amikacin following intravenous regional limb perfusion (IVRLP) with two different doses, and to compare their ability to reach target concentrations for bacterial isolates from common orthopedic conditions. Randomized crossover experiment. Six adult horses. Horses received IVRLP with 2 and 3 g of amikacin in the cephalic vein of alternate limbs (20 minutes tourniquet application and ≥14 days washout period). Amikacin concentrations were quantified in synovial fluid collected from the middle carpal and metacarpophalangeal joints at 25 minutes, and 24, 36, and 48 hours after IVRLP. Minimum inhibitory concentrations (MIC) were determined from equine bacterial isolates and ability to reach target amikacin concentrations were compared. Overall, middle carpal joint amikacin concentrations were higher following IVRLP with 3 g amikacin compared to 2 g (P=.031), with significant differences at 25 minutes (P=.002) and 24 hours (P=.021). No differences were observed between doses in the metacarpophalangeal joint (P=.267). Target amikacin concentrations for Staphylococcus aureus and coagulase-negative staphylococci were achieved in middle carpal and metacarpophalangeal joints at 25 minutes with both dosages and for Escherichia coli and Actinobacillus spp. in the middle carpal joint at 25 minutes with 3 g. Target concentrations were not achieved for Enterococcus spp, Pseudomonas spp, or Streptococcus equi ssp. zooepidemicus. A 3 g amikacin dose is not justified in the majority of distal limb injuries, but should be reserved for isolates with an MIC higher than that achievable with a 2 g dose. Daily IVRLP may be necessary based on our results.

Amikacin Optimal Exposure Targets in the Hollow-Fiber System Model of Tuberculosis.

Aminoglycosides such as amikacin are currently used for the treatment of multidrug-resistant tuberculosis (MDR-TB). However, formal pharmacokinetic/pharmacodynamic (PK/PD) studies to identify amikacin exposures and dosing schedules that optimize Mycobacterium tuberculosis killing have not been performed. It is believed that aminoglycosides do not work well under acidic conditions, which, if true, would mean poor sterilizing activity against semidormant bacilli at low pH. We performed time-kill studies to compare the bactericidal effect of amikacin in log-phase-growth bacilli with the sterilizing effect in semidormant bacilli at pH 5.8 in broth. In log-phase M. tuberculosis at normal pH versus semidormant M. tuberculosis at pH 5.8, the maximal kill (Emax) estimate and 95% confidence interval (CI) were 5.39 (95% CI, 4.91 to 5.63) versus 4.88 (CI, 4.46 to 5.22) log10 CFU/ml, while the concentration mediating 50% of Emax (EC50) was 1.0 (CI, 0. 0.86 to 1.12) versus 0.60 (CI, 0.50 to 0.66) times the MIC, respectively. Thus, the optimal exposures and kill rates identified for log-phase M. tuberculosis will be optimal even for semidormant bacilli. Next, we performed exposure-response and dose-scheduling studies in the hollow-fiber system model of tuberculosis using log-phase M. tuberculosis. We recapitulated the amikacin concentration-time profiles observed in lungs of patients treated over 28 days. The PK/PD index linked to M. tuberculosis kill was the peak concentration (Cmax)-to-MIC ratio (r2 > 0.99), closely followed by the area under the concentration-time curve from 0 to 24 h (AUC0–24)-to-MIC ratio (r2 = 0.98). The EC90 was a Cmax/MIC ratio of 10.13 (95% CI, 7.73 to 12.48). The EC90 is the dosing target for intermittent therapy that optimizes cure in TB programs for MDR-TB patients.

Amikacin use and therapeutic drug monitoring in adults: do dose regimens and drug exposures affect either outcome or adverse events? A systematic review.

The objectives of this study were to identify the amikacin dosage regimens and drug concentrations consistent with good outcomes and to determine the drug exposures related to nephrotoxicity and ototoxicity. A literature review was conducted in Medline, EMBASE and the Cochrane Central Register of Controlled Trials. Full journal articles reporting randomized controlled trials, controlled clinical trials, interrupted time series trials, and controlled before and after studies involving amikacin therapeutic drug monitoring (TDM) and dose adjustment were considered for inclusion. Seventeen studies for inclusion were identified, comprising 1677 participants. Amikacin doses ranged from 11 to 15 mg/kg/day with 13 studies using 15 mg/kg/day. Studies were generally designed to compare different aminoglycosides rather than to assess concentration-effect relationships. Only 11 papers presented data on target concentrations, rate of clinical cure and toxicity. Target peak concentrations ranged from 15 to 40 mg/L and target troughs were typically <10 or <5 mg/L. It was not clear whether these targets were achieved. Measured peaks averaged 28 mg/L for twice-daily dosing and 40-45 mg/L for once-daily dosing; troughs averaged 5 and 1-2 mg/L, respectively. Fifteen of the included studies reported rates of nephrotoxicity; auditory and vestibular toxicities were reported in 12 and 8 studies. This systematic review found little published evidence to support an optimal dosage regimen or TDM targets for amikacin therapy. The use of alternative approaches, such as consensus opinion and a review of current practice, will be required to develop guidelines to maximize therapeutic outcomes and minimize toxicity with amikacin.

Amikacin in Critically Ill Patients: A Review of Population Pharmacokinetic Studies.

Amikacin is an aminoglycoside commonly used in intensive care units for the treatment of patients with life-threatening Gram-negative infections. Although aminoglycosides are extensively used, the accurate determination of their optimal dosage is complicated by marked intra- and interindividual variability in intensive care unit patients. Amikacin pharmacokinetics have been described in numerous studies over the past 25 years. This review presents a synthesis of the population pharmacokinetic models for amikacin described in critically ill patients. The objective was to determine whether there was a consensus on a structural model and which covariates had been identified. A literature search was conducted from the PubMed database, from its inception up until December 2015, using the following terms: 'amikacin', 'pharmacokinetic(s)', 'population', 'model(ling)' and 'nonlinear mixed effect'. Articles were excluded if they were not pertinent. The reference lists of all selected articles were also evaluated. Ten articles were included in this review: pharmacokinetics of amikacin were described by a one-compartment or a two-compartment model. Various covariates were tested, but only two (creatinine clearance and total body weight) were included in almost all of the described models. After inclusion of these covariates, the interindividual variability (range) in clearance and the volume of distribution were 44.4 % (28.2-69.4 %) and 31.3 % (8.1-44.7 %), respectively. The residual variability (range) was around 21.0% (9.0-31.0 %), using a proportional model, and for a combined model (proportional/additive), the median (range) values were 0.615 mg/L (0.2-1.03 mg/L) and 29.2 % (26.8-31.6 %). This review highlights the different population pharmacokinetic models for amikacin developed in critically ill patients over the past decades and proposes relevant information for clinicians and researchers. To optimize amikacin dosage, this review points out the relevant covariates according to the target population. In a population of critically ill patients, dose optimization mainly depends on creatinine clearance and total body weight. New pharmacokinetic population studies could be considered, with new covariates of interest to be tested in model building and to further explain variability. Another future perspective could be external evaluation of previously published models.

Influence of Renal Replacement Modalities on Amikacin Population Pharmacokinetics in Critically Ill Patients on Continuous Renal Replacement Therapy.

The objective of this study was to describe amikacin pharmacokinetics (PK) in critically ill patients receiving equal doses (30 ml/kg of body weight/h) of continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodiafiltration (CVVHDF). Patients receiving amikacin and undergoing CVVH or CVVHDF were eligible. Population pharmacokinetic analysis and Monte Carlo simulation were undertaken using the Pmetrics software package for R. Sixteen patients (9 undergoing CVVH, 11 undergoing CVVHDF) and 20 sampling intervals were analyzed. A two-compartment linear model best described the data. Patient weight was the only covariate that was associated with drug clearance. The mean ± standard deviation parameter estimates were 25.2 ± 17.3 liters for the central volume, 0.89 ± 1.17 h(-1) for the rate constant for the drug distribution from the central to the peripheral compartment, 2.38 ± 6.60 h(-1) for the rate constant for the drug distribution from the peripheral to the central compartment, 4.45 ± 2.35 liters/h for hemodiafiltration clearance, and 4.69 ± 2.42 liters/h for hemofiltration clearance. Dosing simulations for amikacin supported the use of high dosing regimens (≥25 mg/kg) and extended intervals (36 to 48 h) for most patients when considering PK/pharmacodynamic (PD) targets of a maximum concentration in plasma (Cmax)/MIC ratio of ≥8 and a minimal concentration of ≤2.5 mg/liter at the end of the dosing interval. The mean clearance of amikacin was 1.8 ± 1.3 liters/h by CVVHDF and 1.3 ± 1 liters/h by CVVH. On the basis of simulations, a strategy of an extended-interval high loading dose of amikacin (25 mg/kg every 48 h) associated with therapeutic drug monitoring (TDM) should be the preferred approach for aminoglycoside treatment in critically ill patients receiving continuous renal replacement therapy (CRRT). (This study is a substudy of a trial registered at ClinicalTrials.gov under number NCT01403220.).

Bayesian Network to Optimize the First Dose of Antibiotics: Application to Amikacin

Objective: To construct and validate a network to predict the first dose of amikacin. Methods: Anthropometric and therapeutic data were recorded for 120 patients. Bayesian network (BN) was built to predict the dose to achieve a fixed target peak concentration of 64 mg/l. In 40 subjects, doses predicted with the BN (BND) and based on body weight (BWD) were compared with adjusted doses calculated using a pharmacokinetic software (MM-USCPACK; BID). Results: The calculated dose differed by &lt;20% from the ideal dose in 62.5% of the patients with the BN and in 43.8% of the patients with the BW. Conclusion: BN is a promising approach to optimize the prediction of the first dose.

A Prospective Randomized Trial Comparing a Combined Regimen of Amikacin and Levofloxacin to Levofloxacin Alone as Prophylaxis in Transrectal Prostate Needle Biopsy.

We investigated whether addition of amikacin to levofloxacin-based antimicrobial prophylaxis reduces febrile urinary tract infections after transrectal ultrasound-guided prostate needle biopsy (TRUSB). A total of 447 patients undergoing TRUSB were prospectively randomized into two groups. The 230 patients in Group A were given one oral dose of levofloxacin 400 mg prior to TRUSB; the 217 patients in Group B each received the same dose of levofloxacin and one 200 mg intravenous dose of amikacin. Patients' characteristics were assessed prior to TRUSB and their symptoms were checked after the TRUSB. Both regimens were well tolerated with no side effects. No statistically significant difference in patients' characteristics, or in incidence of inflammation- or infection-related symptoms was seen between the two groups; nor any significant difference among those who developed fever and those who did not. Two Group A patients and one Group B patient developed febrile urinary tract infections. Accountable pathogens determined by urine and blood cultures were fluoroquinolone-resistant E.coli and extended-spectrum β-lactamase-producing E.coli. All pathogens isolated were levofloxacin-resistant, amikacin-susceptible species. Although the present study was under-powered by unexpectedly low overall incidence of febrile urinary tract infections, addition of one intravenous administration of amikacin to one oral administration of levofloxacin showed no advantage compared with levofloxacin alone as antimicrobial prophylaxis in TRUSB. Strikingly, all pathogens isolated from febrile patients were sensitive to amikacin in vitro. Therefore, further understanding of amikacin's drug kinetics in the prostate is necessary to develop a more efficient drug delivery system for amikacin.

Therapeutic monitoring of amikacin and gentamicin in critically and noncritically ill patients.

Objective:Therapeutic drug monitoring (TDM) enables individualization in the treatment to optimize clinical benefit and minimize drugs' side effects. Critically ill septic patients represent a challenge for antimicrobial treatment because of pathophysiological impact of sepsis on pharmacokinetics of drugs. The aim of this study was to assess the appropriateness of gentamicin and amikacin dosing in critically and noncritically ill patients, as well as to estimate the need for its regular therapeutic monitoring.Subjects and Methods:It was a prospective study which included 31 patients on gentamicin and 16 patients on amikacin from four different units who met the inclusion criteria. Trough concentrations of drugs were measured in serum just before third or fourth dose of antibiotic, whereas peak concentrations were measured in serum 1 h after the completion of drug administration (steady state). Relevant data on patients' clinical course of disease, comorbidities, and concomitant medication were collected from medical charts in order to identify their possible influence on drugs' concentrations.Results:Peak concentrations of amikacin were in reference range in 81.8% critically ill and in 80% of noncritically ill patients (P = 0.931). Peak concentrations of gentamicin were in reference range in 88.9% critically ill and in 77.3% of noncritically ill patients (P = 0.457).Conclusion:Serum concentrations of aminoglycosides (amikacin and gentamicin) were in reference range in most of the patients in our study, suggesting that dosing of these drugs in the University Hospital Clinical Center, Banja Luka, was adequate. In patients without kidney or liver disease, regular TDM of aminoglycosides is not necessary.

Serum Creatinine Levels May Not Necessarily Reflect a True Renal Function to Adjust Amikacin Dose in Paraplegic Patient: A Case Report and Literature Review

To estimate glomerular filtration rate as an indicator of kidney function, clearance of endogenous creatinine is usually used despite its unreliability due to influence of several factors including age, gender, muscle mass and interferences within methods. Although there is emergence of better markers like serum cystatin-C, creatinine clearance continues to be used routinely as a marker of renal function to date. In the present case study we describe only slightly elevation of serum creatinine associated with high serum drug concentration 27 mg/L “trough” and 41 mg/L “peak”, respectively in a paraplegic patient treated with initially reduced dose (500 mg/day) of an aminoglycoside antibacterial drug (amikacin). The relatively little increment of serum creatinine in this case might be related to underlying pathology resulting in low production of creatinine, which does not essentially reflect the true renal function. Methodological challenges during GFR estimation and risk of renal impairment in Spinal Cord Injury (SCI) patents are also discussed in context with literature review.

PROSPECTIVE VALIDATION OF A MODEL-BASED DOSING REGIMEN FOR AMIKACIN IN NEONATES: FEASIBLE AND RELEVANT

IntroductionA neonatal amikacin dosing regimen was previously developed based on a population pharmacokinetic model. The aim of the current study was to prospectively validate this model-derived dosing regimen.MethodsFirst, early (before and after second dose) therapeutic drug monitoring (TDM) observations were evaluated for achieving target trough (&lt;3 mg/L) and peak (&gt;24 mg/L) levels. Secondly, observed concentrations were compared with model-predicted concentrations, whereby the results of an NPDE (normalized prediction distribution error) were considered as well. Subsequently, Monte Carlo simulations were performed. Finally, remaining causes limiting amikacin predictability (prescription errors and disease characteristics of outliers) were explored.ResultsIn 579 neonates [median (range) birth bodyweight 2285 (420–4850) g, postnatal age 2 (1–30) days, gestational age 34 (24–41) weeks], 90.5% of early peak levels reached 24 mg/L and 60.2% of trough levels was &lt;3 mg/L (93.4% ≤5 mg/L). Observations were accurately predicted by the model without bias, which was confirmed by the NPDE. Monte Carlo simulations showed that peak concentrations &gt;24 mg/L were reached in almost all patients. Trough values &lt;3 mg/L were documented in 78–100% and 45–96% of simulated cases, respectively, when ibuprofen was co-administered or not. Suboptimal trough levels were found in patient subgroups with postnatal age &lt;14 days and current weight &gt;2000g.ConclusionsProspective validation of a model-based neonatal amikacin dosing regimen resulted in optimized peak and trough concentrations in almost all patients. Adapted dosing for patients with suboptimal trough levels was proposed. Besides improving dosing individualization, feasibility and relevance of neonatal prospective validation studies was demonstrated.

Amikacin Pharmacokinetics/Pharmacodynamics in a Novel Hollow-Fiber Mycobacterium abscessus Disease Model.

The treatment of pulmonary Mycobacterium abscessus disease is associated with very high failure rates and easily acquired drug resistance. Amikacin is the key drug in treatment regimens, but the optimal doses are unknown. No good preclinical model exists to perform formal pharmacokinetics/pharmacodynamics experiments to determine these optimal doses. We developed a hollow-fiber system model of M. abscessus disease and studied amikacin exposure effects and dose scheduling. We mimicked amikacin human pulmonary pharmacokinetics. Both amikacin microbial kill and acquired drug resistance were linked to the peak concentration-to-MIC ratios; the peak/MIC ratio associated with 80% of maximal kill (EC80) was 3.20. However, on the day of the most extensive microbial kill, the bacillary burden did not fall below the starting inoculum. We performed Monte Carlo simulations of 10,000 patients with pulmonary M. abscessus infection and examined the probability that patients treated with one of 6 doses from 750 mg to 4,000 mg would achieve or exceed the EC80. We also examined these doses for the ability to achieve a cumulative area under the concentration-time curve of 82,232 mg · h/liter × days, which is associated with ototoxicity. The standard amikacin doses of 750 to 1,500 mg a day achieved the EC80 in ≤ 21% of the patients, while a dose of 4 g/day achieved this in 70% of the patients but at the cost of high rates of ototoxicity within a month or two. The susceptibility breakpoint was an MIC of 8 to 16 mg/liter. Thus, amikacin, as currently dosed, has limited efficacy against M. abscessus. It is urgent that different antibiotics be tested using our preclinical model and new regimens developed.

Impact of an inducement to give high doses of amikacin and gentamicin on serum concentrations in critically ill patients with severe sepsis

Low first-dose peak serum concentrations of amikacin and gentamicin are reported in intensive care unit (ICU) patients.1

Prospective Evaluation of a Model-Based Dosing Regimen for Amikacin in Preterm and Term Neonates in Clinical Practice.

Based on a previously derived population pharmacokinetic model, a novel neonatal amikacin dosing regimen was developed. The aim of the current study was to prospectively evaluate this dosing regimen. First, early (before and after second dose) therapeutic drug monitoring (TDM) observations were evaluated for achieving target trough (<3 mg/liter) and peak (>24 mg/liter) levels. Second, all observed TDM concentrations were compared with model-predicted concentrations, whereby the results of a normalized prediction distribution error (NPDE) were considered. Subsequently, Monte Carlo simulations were performed. Finally, remaining causes limiting amikacin predictability (i.e., prescription errors and disease characteristics of outliers) were explored. In 579 neonates (median birth body weight, 2,285 [range, 420 to 4,850] g; postnatal age 2 days [range, 1 to 30 days]; gestational age, 34 weeks [range, 24 to 41 weeks]), 90.5% of the observed early peak levels reached 24 mg/liter, and 60.2% of the trough levels were <3 mg/liter (93.4% ≤5 mg/liter). Observations were accurately predicted by the model without bias, which was confirmed by the NPDE. Monte Carlo simulations showed that peak concentrations of >24 mg/liter were reached at steady state in almost all patients. Trough values of <3 mg/liter at steady state were documented in 78% to 100% and 45% to 96% of simulated cases with and without ibuprofen coadministration, respectively; suboptimal trough levels were found in patients with postnatal age <14 days and current weight of >2,000 g. Prospective evaluation of a model-based neonatal amikacin dosing regimen resulted in optimized peak and trough concentrations in almost all patients. Slightly adapted dosing for patient subgroups with suboptimal trough levels was proposed. This model-based approach improves neonatal dosing individualization.

Subinhibitory Doses of Aminoglycoside Antibiotics Induce Changes in the Phenotype of Mycobacterium abscessus.

Subinhibitory doses of antibiotics have been shown to cause changes in bacterial morphology, adherence ability, and resistance to antibiotics. In this study, the effects of subinhibitory doses of aminoglycoside antibiotics on Mycobacterium abscessus were investigated. The treatment of M. abscessus cells with subinhibitory doses of amikacin was found to change their colony from a smooth to a rough morphotype and increase their ability to adhere to a polyvinylchloride plate, aggregate in culture, and resist phagocytosis and killing by macrophages. M. abscessus cells treated with a subinhibitory dose of amikacin also became more potent in Toll-like receptor 2 (TLR-2) stimulation, leading to increased tumor necrosis factor alpha (TNF-α) production by macrophages. The MAB_3508c gene was shown to play a role in mediating these phenotypic changes, as its expression in M. abscessus cells was increased when they were treated with a subinhibitory dose of amikacin. In addition, overexpression of MAB_3508c in M. abscessus cells caused changes similar to those induced by subinhibitory doses of amikacin, including a switch from smooth to rough colony morphology, increased ability to aggregate in liquid culture, decreased motility, and increased resistance to killing by macrophages. These findings suggest the importance of using sufficient doses of antibiotics for the treatment of M. abscessus infections.

Effect of Kidney Function on Drug Kinetics and Dosing in Neonates, Infants, and Children.

Neonates, infants, and children differ from adults in many aspects, not just in age, weight, and body composition. Growth, maturation and environmental factors affect drug kinetics, response and dosing in pediatric patients. Almost 80 % of drugs have not been studied in children, and dosing of these drugs is derived from adult doses by adjusting for body weight/size. As developmental and maturational changes are complex processes, such simplified methods may result in subtherapeutic effects or adverse events. Kidney function is impaired during the first 2 years of life as a result of normal growth and development. Reduced kidney function during childhood has an impact not only on renal clearance but also on absorption, distribution, metabolism and nonrenal clearance of drugs. ‘Omics’-based technologies, such as proteomics and metabolomics, can be leveraged to uncover novel markers for kidney function during normal development, acute kidney injury, and chronic diseases. Pharmacometric modeling and simulation can be applied to simplify the design of pediatric investigations, characterize the effects of kidney function on drug exposure and response, and fine-tune dosing in pediatric patients, especially in those with impaired kidney function. One case study of amikacin dosing in neonates with reduced kidney function is presented. Collaborative efforts between clinicians and scientists in academia, industry, and regulatory agencies are required to evaluate new renal biomarkers, collect and share prospective pharmacokinetic, genetic and clinical data, build integrated pharmacometric models for key drugs, optimize and standardize dosing strategies, develop bedside decision tools, and enhance labels of drugs utilized in neonates, infants, and children.