Amikacin Serum Concentrations Research Articles

Early-Phase Adverse Effects and Management of Liposomal Amikacin Inhalation for Refractory Mycobacterium avium Complex Lung Disease in Real-World Settings

PurposeAmikacin liposome inhalation suspension (ALIS), which efficiently allows amikacin to reach the pulmonary periphery for effect while minimising systemic adverse effects, was recently approved for treating Mycobacterium avium complex (MAC) infections. The international Phase 3 open-label clinical trials showed promising results, contributing to sputum culture conversion, but few studies have examined the efficacy and adverse effects of ALIS using real-world data. We identified the clinical outcome and adverse effects of ALIS in the early phase of treatment, for more effective and safe use in clinical practice.Patients and MethodsThe study population consisted of patients with MAC lung disease (MAC-LD), introduced to ALIS therapy after July 2021 at Keio University Hospital due to poor response to multidrug therapy. The sputum smear/culture results, symptoms, adverse effects, and the serum amikacin concentrations of the early phase of ALIS inhalation therapy were examined.ResultsA total of 11 patients (9 women; median age 64.6 years) were included in this study. The median disease duration of MAC-LD was 13.7 years, and all patients exhibited a positive culture at the beginning of ALIS inhalation. Three of the six patients (50.0%) who were initially sputum-smear-positive were confirmed to have become sputum-smear-negative within one month, including one culture conversion. ALIS inhalation therapy caused some adverse effects in nine patients (81.8%); however, no serious systemic adverse effects were observed. The most common adverse effect was hoarseness (72.7%), which mostly occurred around 1 week after initiation. The medians of peak serum amikacin concentrations were 1.4 and 2.3 μg/mL for the first and third inhalations, respectively. Trough serum concentrations just before the third inhalation were <1.2 μg/mL in all patients.ConclusionALIS therapy might be a treatment option for patients with refractory MAC infection with long disease duration and a poor response to guideline-based therapy.

Relationship between amikacin pharmacokinetics and biological parameters associated with organ dysfunction: a case series study of critically ill patients with intra-abdominal sepsis

ObjectivesThis study aimed to evaluate the relationship between amikacin pharmacokinetics and the biomarkers associated with organ dysfunction in critically ill patients with intra-abdominal sepsis.MethodsA case series involving critically ill patients...

Pharmacokinetics of Intraperitoneal Vancomycin and Amikacin in Automated Peritoneal Dialysis Patients With Peritonitis.

Objective: The study aimed to evaluate the vancomycin and amikacin concentrations in serum and dialysate for automatic peritoneal dialysis (APD) patients. Methods: A total of 558 serum and dialysate samples of 12 episodes of gram-positive and 18 episodes of gram-negative peritonitis were included to investigate the relationship between vancomycin and amikacin concentrations in serum and dialysate on the first and third days of treatment. Samples were analysed 30, 120 min, and 48 h after intraperitoneal administration of vancomycin in peritonitis caused by gram-positive agents and 30, 120 min, and 24 h after intraperitoneal administration of amikacin in peritonitis caused by gram-negative agents. Vancomycin was administered every 72 h and amikacin once a day. The target therapeutic concentration of amikacin was 25–35 mg/l at the peak moment and 4–8 mg/l at the trough moment; and after 48 h for vancomycin, 15–20 mg/l at the trough moment. Results: For peritonitis caused by gram-negative agents, at the peak moment, therapeutic levels of amikacin were reached in dialysate in 80.7% of patients with evolution to cure and in 50% of patients evaluated as non-cure (p = 0.05). At the trough moment, only 38% were in therapeutic concentrations in the dialysate in the cure group and 42.8% in the non-cure group (p = 1). Peak plasma concentrations were subtherapeutic in 98.4% of the samples in the cure group and in 100% of the non-cure group. At the trough moment, therapeutic concentrations were present in 74.4% of the cure group and 71.4% of the non-cure group (p = 1). Regarding vancomycin and among gram-positive agents, therapeutic levels were reached at the peak moment in 94% of the cure group and 6% of the non-cure group (p = 0.007). After 48 h, 56.8% of the cure group had a therapeutic serum concentration whereas for the non-cure group it was only 33.3% (p = 0.39). Conclusion: Despite a small sample size, we demonstrated peak dialysate amikacin level and peak serum vancomycin level correlates well with Gram-negative and Gram positve peritonitis cure, respectively. It is suggested to study the antibiotics pharmacodynamics for a better understanding of therapeutic success in a larger sample.

Evaluation of Amikacin Pharmacokinetics in Critically Ill Patients with Intra-abdominal Sepsis.

Purpose: Although the current widespread use of amikacin is in intra-abdominal sepsis treatment, its pharmacokinetic changes in the present setting are not yet well known. This study was aimed to evaluate the amikacin pharmacokinetic profile in critically ill patients with intraabdominal sepsis compared to pneumosepsis. Methods: Adult septic patients received amikacin therapy were studied. Patients with intraabdominal sepsis were enrolled in group 1 (n=16), and patients with pneumosepsis were enrolled in group 2 (n=13). The amikacin serum concentrations were evaluated in the first, second, fourth and sixth hours after initiating 30-minute infusion. The pharmacokinetic parameters were calculated for each patient. Results: There was no significant difference in the volume of distribution between the two groups (0.33±0.08 vs. 0.28±0.10 L/kg, P=0.193). The amikacin clearance was significantly lower in group 1 compared to group 2 (58.5±21.7 vs. 83.9±37.0 mL/min, P=0.029). There was no significant correlation between amikacin clearance and creatinine clearance estimated by Cockcroft-Gault formula in all patients (P=0.206). The half-life was significantly longer in group 1 compared to group 2 (5.3±2.8 vs. 3.4±3.2 hours, P=0.015). Conclusion: Pathophysiologic changes following intra-abdominal sepsis can affect amikacin pharmacokinetics behavior. The clearance and half-life may change, but the alteration of the volume of distribution is not significantly different in comparison with pneumosepsis. Further studies are required to evaluate the pharmacokinetic variables of amikacin in critically ill patients with intra-abdominal sepsis.

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.

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.

Pharmacokinetics of high-dose nebulized amikacin in ventilated critically ill patients.

Antibiotic nebulization theoretically allows the delivery of high doses to the lungs together with limited systemic exposure and toxicity. This study aimed to describe amikacin pharmacokinetics, and especially its absorption, in patients treated with high-dose nebulized amikacin. Twenty critically ill patients experiencing ventilator-associated pneumonia received a 20 mg/kg infusion of amikacin, followed by either three other infusions or three nebulizations of 60 mg/kg amikacin. An extensive sampling regimen allowed measurement of amikacin serum concentrations at 0.5, 1, 1.5, 2, 3, 4, 6, 10 and 24 h after each administration. Amikacin pharmacokinetics was studied by population compartmental modelling. Amikacin pharmacokinetics was best described using a two-compartment structural model with first-order distribution and elimination, in which lung absorption was described using a transit model. Estimated means (interindividual variability) of the main parameters were: bioavailability F = 2.65% (22.1%); transit compartments n = 1.58 (fixed); transit constant ktr = 1.38 h-1 (33.4%); central volume Vc = 10.2 L (10.5%); and elimination constant k10 = 0.488 h-1 (35.8%). The addition of interoccasion variability on F (44.0%) and k10 (41.7%) allowed the description of intraindividual variability of bioavailability and elimination. Amikacin clearance was positively correlated with baseline creatinine clearance. Our pharmacokinetic model provided an accurate description of amikacin concentrations following nebulization. There was wide interindividual and interoccasion variability in the absorption and elimination of amikacin. Nevertheless, systemic exposure after nebulization was always much lower than after infusion, an observation suggesting that nebulized high doses are safe in this regard and may be used to treat ventilator-associated pneumonia.

Impact of 30 mg/kg amikacin and 8 mg/kg gentamicin on serum concentrations in critically ill patients with severe sepsis.

Low first-dose peak serum concentrations of amikacin and gentamicin are commonly reported in ICU patients. The present study aimed to assess whether 30 mg/kg amikacin or 8 mg/kg gentamicin achieved target concentrations in ICU patients with severe sepsis. Sixty-three ICU patients (Simplified Acute Physiology Score II = 43 ± 16) with severe sepsis and an indication for intravenous amikacin (n = 47) or gentamicin (n = 16) were included. The first (30 mg/kg amikacin; 8 mg/kg gentamicin) and subsequent doses and corresponding peak concentrations (30 min after the completion of an infusion) were recorded. French guideline target concentrations were ≥60 and ≥30 mg/L for amikacin and gentamicin, respectively. A target pharmacokinetic/pharmacodynamic ratio of 10 × MIC was also measured. Pulmonary, abdominal and urinary tract infections were diagnosed in 56 patients. Infection was confirmed in 37 patients (59%). The targeted first-dose peak concentration was achieved in 37/63 patients (59%) [amikacin 36/47 (77%) and gentamicin 1/16 (6%)], and 59/63 patients (94%) achieved the pharmacokinetic/pharmacodynamic ratio using the MIC data that were available from 21 patients. However, the second dose of aminoglycoside was withheld because of high trough concentrations in nearly half of patients who did not have renal dysfunction. In this study, 30 mg/kg amikacin and 8 mg/kg gentamicin led to target peak serum concentrations in 59% of patients.

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

Amikacin population pharmacokinetics among paediatric burn patients

IntroductionThe objectives of this study were to (1) determine the pharmacokinetics of amikacin among children with severe burn and (2) identify influential covariates. MethodsPopulation-based pharmacokinetic modelling was performed in NONMEM 7.2 for hospitalized children who received amikacin at 10–20mg/kg divided two, three, or four times per day as part of early empiric treatment of presumed burn-related sepsis. ResultsThe analysis included data from 70 patients (6 months to 17 years) with 282 amikacin serum concentrations. Amikacin's mean Cmax was 33.2±9.4μg/mL and the mean Cmin was 3.8±4.6μg/mL. The final covariate model estimated clearance as 5.98L/h/70kg (4.97–6.99, 95% CI), the volume of distribution in the central compartment as 16.7L/70kg (14.0–19.4, 95% CI), the volume of distribution in the peripheral compartment as 40.1L/70kg (15.0–80.4, 95% CI), and the inter-compartmental clearance as 3.38L/h/70kg (2.44–4.32, 95% CI). In multivariate analyses, current weight (P<0.001) was a significant covariate, while age, sex, height, serum creatinine, C-reactive protein, platelet count, the extent and type of burn, and concomitant vancomycin administration did not influence amikacin pharmacokinetics. DiscussionChildren with burn featured elevated amikacin clearance when compared to healthy adult volunteers. However, peak amikacin concentrations are comparable to those attained in other critically-ill children, suggesting that elevated amikacin clearance may not result in sub-therapeutic antibacterial effects. In this study, we found that amikacin displays two-compartment pharmacokinetics, with weight exerting a strong effect upon amikacin clearance. Further pharmacodynamic studies are needed to establish the optimal dosing regimen for amikacin in paediatric burn patients.

Amikacin Population Pharmacokinetics in Critically Ill Kuwaiti Patients

Amikacin pharmacokinetic data in Kuwaiti (Arab) intensive care unit (ICU) patients are lacking. Fairly sparse serum amikacin peak and trough concentrations data were obtained from adult Kuwaiti ICU patients. The data were analysed using a nonparametric adaptive grid (NPAG) maximum likelihood algorithm. The estimations of the developed model were assessed using mean error (ME) as a measure of bias and mean squared error (MSE) as a measure of precision. A total of 331 serum amikacin concentrations were obtained from 56 patients. The mean (±SD) model parameter values found were V c = 0.2302 ± 0.0866 L/kg, k slope = 0.004045 ± 0.00705 min per unit of creatinine clearance, k 12 = 2.2121 ± 5.506 h−1, and k 21 = 1.431 ± 2.796 h−1. The serum concentration data were estimated with little bias (ME = −0.88) and good precision (MSE = 13.08). The present study suggests that amikacin pharmacokinetics in adult Kuwaiti ICU patients are generally rather similar to those found in other patients. This population model would provide useful guidance in developing initial amikacin dosage regimens for such patients, especially using multiple model (MM) dosage design, followed by appropriate Bayesian adaptive control, to optimize amikacin dosage regimens for each individual patient.

Once-Daily Amikacin Dosing in Burn Patients Treated with Continuous Venovenous Hemofiltration

Amikacin clearance can be increased in burn injury, which is often complicated by renal insufficiency. Little is known about the impact of renal replacement therapies, such as continuous venovenous hemofiltration (CVVH), on amikacin pharmacokinetics. We retrospectively examined the clinical pharmacokinetics, bacteriology, and clinical outcomes of 60 burn patients given 15 mg/kg of body weight of amikacin in single daily doses. Twelve were treated with concurrent CVVH therapy, and 48 were not. The pharmacodynamic target of ≥10 for the maximum concentration of drug in serum divided by the MIC (C(max)/MIC) was achieved in only 8.5% of patients, with a small reduction of C(max) in patients receiving CVVH and no difference in amikacin clearance. Mortality and burn size were greater in patients who received CVVH. Overall, 172 Gram-negative isolates were recovered from the blood cultures of 39 patients, with amikacin MIC data available for 82 isolates from 24 patients. A 10,000-patient Monte Carlo simulation was conducted incorporating pharmacokinetic and MIC data from these patients. The cumulative fraction of response (CFR) was similar in CVVH and non-CVVH patients. The CFR rates were not significantly improved by a theoretical 20 mg/kg amikacin dose. Overall, CVVH did not appear to have a major impact on amikacin serum concentrations. The low pharmacodynamic target attainment appears to be primarily due to higher amikacin MICs rather than more rapid clearance of amikacin related to CVVH therapy.

Quantification of Amikacin in Bronchial Epithelial Lining Fluid in Neonates

Amikacin efficacy is based on peak concentrations and the possibility of reaching therapeutic levels at the infection site. This study aimed to describe amikacin concentrations in the epithelial lining fluid (ELF) through bronchoalveolar lavage (BAL) in newborns. BAL fluid was collected in ventilated neonates treated with intravenous (i.v.) amikacin. Clinical characteristics, amikacin therapeutic drug monitoring serum concentrations, and the concentrations of urea in plasma were extracted from the individual patient files. Amikacin and urea BAL fluid concentrations were determined using liquid chromatography with pulsed electrochemical detection (LC-PED) and capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C(4)D), respectively. ELF amikacin concentrations were converted from BAL fluid concentrations through quantification of dilution (urea in plasma/urea in BAL fluid) during the BAL procedure. Twenty-two observations in 17 neonates (postmenstrual age, 31.9 [range, 25.1 to 41] weeks; postnatal age, 3.5 [range, 2 to 37] days) were collected. Median trough and peak amikacin serum concentrations were 2.1 (range, 1 to 7.1) mg/liter and 39.1 (range, 24.1 to 73.2) mg/liter; the median urea plasma concentration was 30 (8 to 90) mg/dl. The median amikacin concentration in ELF was 6.5 mg/liter, the minimum measured concentration was 1.5 mg/liter, and the maximum (peak) was 23 mg/liter. The highest measured ELF concentration was reached between 6 and 14.5 h after i.v. amikacin administration, and an estimated terminal elimination half-life was 8 to 10 h. The median and highest (peak) ELF amikacin concentrations observed in our study population were, respectively, 6.5 and 23 mg/liter. Despite the frequent use of amikacin in neonatal (pulmonary) infections, this is the first report of amikacin quantification in ELF in newborns.

Pharmacokinetics and Tolerability of BAY41-6551 in Subjects with Chronic Kidney Disease

Abstract Background: BAY41-6551, a drug-device combination in development for adjunctive treatment of Gram-negative pneumonia in mechanically ventilated patients, consists of amikacin formulated for inhalation coupled with the Pulmonary Drug Delivery System (PDDS) Clinical aerosol delivery platform. This study evaluated safety, tolerability, and pharmacokinetics (PK) of BAY41-6551 in subjects with chronic kidney disease (CKD). Single doses of BAY41-6551 (400 mg amikacin) were administered using the PDDS Clinical handheld device to six subjects with mild-to-moderate (Group 1) and six subjects with severe renal impairment (Group 2). Seven subjects with end-stage renal disease (ESRD; Group 3) received single doses of BAY41-6551 on days 1 and 9, with hemodialysis (HD) scheduled 24 h postdose on day 1 and 3 h postdose on day 9. PK analysis was performed on serum, urine, and dialysate samples (Group 3). Individual serum amikacin concentrations in Groups 1 and 2 were below 6 mg/L at all times [mean maximum serum drug concentration (C(max)) 0.94 mg/L and 2.46 mg/L, respectively). In Group 3, serum amikacin concentrations decreased after each HD session, and amikacin area under the serum concentration-time curve from zero to 72 h (AUC(72)) and C(max) values were lower on day 9 than on day 1 (mean AUC(72) 71.5 mg · h/L vs. 151.5 mg · h/L; mean C(max) 2.09 mg/L vs. 6.16 mg/L). The amounts of amikacin removed by HD and the dialysate clearance rates were similar on days 1 and 9. No serious adverse events were reported. Single doses of BAY41-6551 were well tolerated in subjects with CKD. HD effectively removed amikacin from serum in subjects with ESRD, and the timing relative to BAY41-6551 administration was an important determinant of systemic amikacin exposure. Nevertheless, standard precautionary measures for intravenous amikacin should apply for patients receiving BAY41-6551, and dose adjustments and/or dialysis should be considered for subjects with severe renal impairment.

Pharmacokinetics and Tolerability of Amikacin Administered as BAY41-6551 Aerosol in Mechanically Ventilated Patients with Gram-Negative Pneumonia and Acute Renal Failure

BAY41-6551, a drug-device combination in development for adjunctive treatment of Gram-negative pneumonia in intubated and mechanically ventilated patients, consists of amikacin formulated for inhalation coupled with the Pulmonary Drug Delivery System (PDDS) Clinical aerosol delivery platform. Given the predominantly renal clearance of aminoglycosides, understanding systemic amikacin exposure and safety during administration of BAY41-6551 to patients with acute renal failure (ARF) is clinically important. Seven mechanically ventilated patients with Gram-negative pneumonia and ARF receiving continuous veno-venous hemodiafiltration (CVVHDF) were treated with multiple administrations of BAY41-6551 400 mg amikacin twice daily using the PDDS Clinical on-ventilator device [in addition to standard intravenous (i.v.) antimicrobial therapy]. CVVHDF parameters were recorded and a PK analysis was performed using serum, urine, and bronchoalveolar lavage fluid samples. Maximum serum amikacin concentration [median 1.93 (range: 0.63-3.99) mg/L] and area under the concentration-time curve from zero to 12 h on day 3 [median 19.32 (range 6.32-36.87) mg · h/L] were elevated compared with mechanically ventilated patients with normal renal function; however, serum amikacin trough concentrations were within accepted safety limits. The median amikacin concentration in epithelial lining fluid [887 (range: 406-12,819) mg/L] was similar to that reported previously in mechanically ventilated patients with normal renal function. BAY41-6551 demonstrated acceptable safety and tolerability with most adverse events (AEs) as expected for the patient population. One serious AE of bronchospasm was attributed to the study medication; no reported AEs were related to the PDDS Clinical device. CVVHDF appears to provide adequate clearance of systemically absorbed amikacin in mechanically ventilated patients with ARF, suggesting that dose adjustments for BAY41-6551 are probably not necessary for this patient population. Nonetheless, the standard precautionary measures for critically ill patients receiving i.v. amikacin should be followed for patients with ARF who are treated with BAY41-6551.

Evaluation of population pharmacokinetic models for amikacin dosage individualization in critically ill patients

Abstract Objectives The aim of this study was to evaluate the reliability for dosage individualization and Bayesian adaptive control of several literature-retrieved amikacin population pharmacokinetic models in patients who were critically ill. Methods Four population pharmacokinetic models, three of them customized for critically-ill patients, were applied using pharmacokinetic software to fifty-one adult patients on conventional amikacin therapy admitted to the intensive care unit. An estimation of patient-specific pharmacokinetic parameters for each model was obtained by retrospective analysis of the amikacin serum concentrations measured (n = 162) and different clinical covariates. The model performance for a priori estimation of the area under the serum concentration-time curve (AUC) and maximum serum drug concentration (Cmax) targets was obtained. Key findings Our results provided valuable confirmation of the clinical importance of the choice of population pharmacokinetic models when selecting amikacin dosages for patients who are critically ill. Significant differences in model performance were especially evident when only information concerning clinical covariates was used for dosage individualization and over the two most critical determinants of clinical efficacy of amikacin i.e. the AUC and Cmax values. Conclusions Only a single amikacin serum level seemed necessary to diminish the influence of population model on dosage individualization.

Evaluation of population pharmacokinetic models for amikacin dosage individualization in critically ill patients

The aim of this study was to evaluate the reliability for dosage individualization and Bayesian adaptive control of several literature-retrieved amikacin population pharmacokinetic models in patients who were critically ill. Four population pharmacokinetic models, three of them customized for critically-ill patients, were applied using pharmacokinetic software to fifty-one adult patients on conventional amikacin therapy admitted to the intensive care unit. An estimation of patient-specific pharmacokinetic parameters for each model was obtained by retrospective analysis of the amikacin serum concentrations measured (n = 162) and different clinical covariates. The model performance for a priori estimation of the area under the serum concentration-time curve (AUC) and maximum serum drug concentration (C(max)) targets was obtained. Our results provided valuable confirmation of the clinical importance of the choice of population pharmacokinetic models when selecting amikacin dosages for patients who are critically ill. Significant differences in model performance were especially evident when only information concerning clinical covariates was used for dosage individualization and over the two most critical determinants of clinical efficacy of amikacin i.e. the AUC and C(max) values. Only a single amikacin serum level seemed necessary to diminish the influence of population model on dosage individualization.

Pharmacokinetics and lung delivery of PDDS-aerosolized amikacin (NKTR-061) in intubated and mechanically ventilated patients with nosocomial pneumonia

IntroductionAminoglycosides aerosolization might achieve better diffusion into the alveolar compartment than intravenous use. The objective of this multicenter study was to evaluate aerosol-delivered amikacin penetration into the alveolar epithelial lining fluid (ELF) using a new vibrating mesh nebulizer (Pulmonary Drug Delivery System (PDDS), Nektar Therapeutics), which delivers high doses to the lungs.MethodsNebulized amikacin (400 mg bid) was delivered to the lungs of 28 mechanically ventilated patients with Gram-negative VAP for 7-14 days, adjunctive to intravenous therapy. On treatment day 3, 30 minutes after completing aerosol delivery, all the patients underwent bronchoalveolar lavage in the infection-involved area and the ELF amikacin concentration was determined. The same day, urine and serum amikacin concentrations were determined at different time points.ResultsMedian (range) ELF amikacin and maximum serum amikacin concentrations were 976.1 (135.7-16127.6) and 0.9 (0.62-1.73) μg/mL, respectively. The median total amount of amikacin excreted in urine during the first and second 12-hour collection on day 3 were 19 (12.21-28) and 21.2 (14.1-29.98) μg, respectively. During the study period, daily through amikacin measurements were below the level of nephrotoxicity. Sixty-four unexpected adverse events were reported, among which 2 were deemed possibly due to nebulized amikacin: one episode of worsening renal failure, and one episode of bronchospasm.ConclusionsPDDS delivery of aerosolized amikacin achieved very high aminoglycoside concentrations in ELF from radiography-controlled infection-involved zones, while maintaining safe serum amikacin concentrations. The ELF concentrations always exceeded the amikacin minimum inhibitory concentrations for Gram-negative microorganisms usually responsible for these pneumonias. The clinical impact of amikacin delivery with this system remains to be determined.Trial RegistrationClinicalTrials.gov Identifier: NCT01021436.

Cerebrospinal Fluid Compartmental Pharmacokinetics of Amikacin in Neonates

To describe and investigate the covariate effects of cerebrospinal fluid (CSF) amikacin pharmacokinetics in neonates, CSF samples were prospectively collected from neonates in whom amikacin had been initiated before a diagnostic lumbar puncture was performed. CSF analysis (amikacin concentration, white blood count [WBC], glucose content, and protein concentration) and amikacin therapeutic drug monitoring results (peak and trough concentrations) in serum were recorded. Correlations (Spearman rank) between the CSF amikacin concentration and the CSF WBC and glucose and protein concentration were investigated. There were 44 CSF amikacin concentrations and 83 serum samples available from 43 neonates (mean postmenstrual age, 36 weeks [range, 26 to 41 weeks]; mean weight, 2.43 kg [range, 0.87 to 3.86 kg]). The median time interval between initiation of amikacin administration and CSF sampling was 25 h (range, 2.5 to 93.7 h). The median amikacin concentration in the CSF was 1.08 mg/liter (range, 0.34 to 2.65 mg/liter), and the mean trough and peak amikacin concentrations in serum were 3.8 +/- 2.5 mg/liter and 35.7 +/- 5.9 mg/liter, respectively. A correlation between CSF amikacin and CSF protein contents (P < 0.01, r = 0.41, 95% confidence interval = 0.13 to 0.63) but not between CSF WBC and CSF glucose was documented. A two-compartment (central and CSF) linear disposition model was used to estimate population pharmacokinetics. The half time for equilibration (T(eq)) between serum and CSF compartments was used as a measure of blood-brain barrier permeability. The T(eq) was 7.58 h (coefficient of variation [CV] = 49.1%) with a partition coefficient of 0.103 (CV = 26.4%). There was no relationship between the T(eq) and CSF WBC, CSF glucose content, or CSF protein content.

An Evaluation of Amikacin Nephrotoxicity in the Hematology/Oncology Population

Amikacin is an aminoglycoside commonly used to provide empirical double gram-negative treatment for febrile neutropenia and other suspected infections. Strategies of extended-interval and conventional dosing have been utilized extensively in the general medical population; however, data are lacking to support a dosing strategy in the hematology/oncology population. To evaluate amikacin-associated nephrotoxicity in an adult hematology/oncology population, a prospective, randomized, open-label trial was conducted at a university-affiliated medical center. Forty patients with a diagnosis consistent with a hematologic/oncologic disorder that required treatment with an aminoglycoside were randomized to either conventional or extended-interval amikacin. The occurrence of nephrotoxicity by means of an increase in serum creatinine and evaluation of efficacy via amikacin serum concentrations with respective pathogens were assessed. The occurrence of nephrotoxicity was similar between the conventional and extended-interval groups, at 10% and 5%, respectively (P = 1.00). Six patients in the conventional group had a positive culture, compared with none in the extended-interval group (P = 0.002). The occurrence of nephrotoxicity was similar between the two dosing regimens, but the distribution of risk factors was variable between the two groups. Efficacy could not be assessed.