scholarly journals An Adaptive Biosystems Engineering Approach towards Modeling the Soluble-to-Insoluble Phase Transition of Clofazimine

Pharmaceutics ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 17
Author(s):  
Andrew R. Willmer ◽  
Steven Dunne ◽  
Rosemary Swanson ◽  
Deepak Almeida ◽  
Nicole C. Ammerman ◽  
...  
Keyword(s):  
Phase Transition ◽  
Drug Disposition ◽  
Drug Loading ◽  
Multidrug Resistant ◽  
Volume Of Distribution ◽  
Compartmental Models ◽  
Information Criteria ◽  
Concentration Data ◽  
Drug Concentrations ◽  
Dependent Change

Clofazimine (CFZ) is a weakly basic, small-molecule antibiotic used for the treatment of mycobacterial infections including leprosy and multidrug-resistant tuberculosis. Upon prolonged oral administration, CFZ precipitates and accumulates within macrophages throughout the host. To model the pharmacokinetics of CFZ, the volume of distribution (Vd) was considered as a varying parameter that increases with continuous drug loading. Fitting the time-dependent change in drug mass and concentration data obtained from CFZ-treated mice, we performed a quantitative analysis of the systemic disposition of the drug over a 20-week treatment period. The pharmacokinetics data were fitted using various classical compartmental models sampling serum and spleen concentration data into separate matrices. The models were constructed in NONMEM together with linear and nonlinear sigmoidal expansion functions to the spleen compartment to capture the phase transition in Vd. The different modeling approaches were compared by Akaike information criteria, observed and predicted concentration correlations, and graphically. Using the composite analysis of the modeling predictions, adaptive fractional CFZ sequestration, Vd and half-life were evaluated. When compared to standard compartmental models, an adaptive Vd model yielded a more accurate data fit of the drug concentrations in both the serum and spleen. Including a nonlinear sigmoidal equation into compartmental models captures the phase transition of drugs such as CFZ, greatly improving the prediction of population pharmacokinetics and yielding further insight into the mechanisms of drug disposition.

scholarly journals Comparative Drug Disposition, Urinary Pharmacokinetics, and Renal Effects of Multilamellar Liposomal Nystatin and Amphotericin B Deoxycholate in Rabbits

2003 ◽  
Vol 47 (12) ◽  
pp. 3917-3925 ◽  
Author(s):  
Andreas H. Groll ◽  
Diana Mickiene ◽  
Vidmantas Petraitis ◽  
Ruta Petraitiene ◽  
Raul M. Alfaro ◽  
...  
Keyword(s):  
Total Dose ◽  
Amphotericin B ◽  
Drug Disposition ◽  
Fungal Infections ◽  
Standard Dose ◽  
Concentration Data ◽  
Drug Concentrations ◽  
Amphotericin B Deoxycholate ◽  
Dose Dependent Decrease ◽  
Dose Dependent

ABSTRACT The comparative drug dispositions, urinary pharmacokinetics, and effects on renal function of multilamellar liposomal nystatin (LNYS; Nyotran) and amphotericin B deoxycholate (DAMB; Fungizone) were studied in rabbits. Drug concentrations were determined by high-performance liquid chromatography as total concentrations of LNYS and DAMB. In comparison to a standard dose of 1 mg of DAMB/kg of body weight, therapeutic dosages of LNYS, i.e., 2, 4, and 6 mg/kg, resulted in escalating maximum concentrations (C max) (17 to 56μ g/ml for LNYS versus 3.36 μg/ml for DAMB; P< 0.001) and values for the area under the concentration-time curve from 0 to 24 h (AUC0-24) (17 to 77μ g · h/ml for LNYS versus 12μ g · h/ml for DAMB; P < 0.001) in plasma but a significantly faster total clearance from plasma (0.117 to 0.080 liter/h/kg for LNYS versus 0.055 liter/h/kg for DAMB; P = 0.013) and a ≤8-fold-smaller volume of distribution at steady state (P = 0.002). Urinary drug concentration data revealed a ≥10-fold-higher C max (16 to 10 μg/ml for LNYS versus 0.96μ g/ml for DAMB; P = 0.015) and a 4- to 7-fold-greater AUC0-24 (63 to 35μ g · h/ml for LNYS versus 8.9μ g · h/ml for DAMB; P = 0.015) following the administration of LNYS, with a dose-dependent decrease in the dose-normalized AUC0-24 in urine (P= 0.001) and a trend toward a dose-dependent decrease in renal clearance. Except for the kidneys, the mean concentrations of LNYS in liver, spleen, and lung 24 h after dosing were severalfold lower than those after administration of DAMB (P,<0.002 to <0.001). Less than 1% each of the total dose of LNYS was recovered from the kidneys, liver, spleen, and lungs; in contrast, a quarter of the total dose was recovered from the livers of DAMB-treated animals. LNYS had dose-dependent effects on glomerular filtration and distal, but not proximal, renal tubular function which did not exceed those of DAMB at the highest investigated dosage of 6 mg/kg. The results of this experimental study demonstrate fundamental differences in the dispositions of LNYS and DAMB. Based on its enhanced urinary exposure, LNYS may offer a therapeutic advantage in systemic fungal infections involving the upper and lower urinary tracts that require therapy with antifungal polyenes.

scholarly journals Pharmacokinetics of 2,000 Milligram Ertapenem in Tuberculosis Patients

2018 ◽  
Vol 62 (5) ◽  
Author(s):  
M. A. Zuur ◽  
S. Ghimire ◽  
M. S. Bolhuis ◽  
A. M. A. Wessels ◽  
R. van Altena ◽  
...  
Keyword(s):  
Central Compartment ◽  
Multidrug Resistant ◽  
Volume Of Distribution ◽  
Interindividual Variation ◽  
Infection Model ◽  
Time Curve ◽  
Once Daily ◽  
Content Type ◽  
Drug Concentrations ◽  
Liquid Chromatography Tandem Mass

ABSTRACT Ertapenem is a carbapenem antibiotic with activity against Mycobacterium tuberculosis . Dose simulations in a hollow-fiber infection model showed that 2,000 mg once daily is an appropriate dose to be tested in clinical studies. Before using this dose in a phase II study, the aim of this prospective pharmacokinetic study was to confirm the pharmacokinetics of 2,000 mg once daily in tuberculosis (TB) patients. Twelve TB patients received a single intravenous dose of 2,000 mg ertapenem as a 30-min infusion. Blood samples were collected at 0, 0.5, 1, 2, 3, 4, 8, 12, and 24 h postadministration. Drug concentrations were measured using a validated liquid chromatography-tandem mass spectrometry assay. A large interindividual variation in the pharmacokinetics of ertapenem was observed. The median (interquartile range) area under the plasma concentration-time curve to infinity (AUC 0–∞ ) was 2,032 (1,751 to 2,346) mg · h/liter, the intercompartmental clearance (CL 12 ) was 1.941 (0.979 to 2.817) liters/h, and the volume of distribution in the central compartment ( V 1 ) was 1.514 (1.064 to 2.210) liters. A more than dose-proportional increase in AUC was observed compared to results reported for 1,000 mg ertapenem in multidrug-resistant TB patients. Based on a MIC of 1.0 mg/liter, 11 out of 12 patients would have reached the target value of unbound drug exceeding the MIC over 40% of the time ( f 40% T >MIC). In conclusion, this study shows that 2,000 mg ertapenem once daily in TB patients reached the expected f 40% T >MIC for most of the patients, and exploration in a phase 2 study can be advocated.

scholarly journals Population Pharmacokinetics and Use of Monte Carlo Simulation To Evaluate Currently Recommended Dosing Regimens of Ciprofloxacin in Adult Patients with Cystic Fibrosis

2001 ◽  
Vol 45 (12) ◽  
pp. 3468-3473 ◽  
Author(s):  
Megan J. Montgomery ◽  
Paul M. Beringer ◽  
Amir Aminimanizani ◽  
Stan G. Louie ◽  
Bertrand J. Shapiro ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Half Life ◽  
Volume Of Distribution ◽  
Therapeutic Drug ◽  
Serum Drug Concentration ◽  
Concentration Data ◽  
Drug Concentrations ◽  
Dosing Regimens

ABSTRACT Pharmacodynamic data on ciprofloxacin indicate that a target area under the concentration-time curve from 0 to 24 h (AUC0–24)/MIC ratio of ≥125 is necessary to achieve optimal bactericidal activity for the treatment of gram-negative pneumonia. The purpose of this prospective study was to (i) develop a pharmacokinetic (PK) model to be utilized for therapeutic drug monitoring (TDM) of ciprofloxacin and (ii) evaluate current ciprofloxacin dosing regimens for pneumonias in cystic fibrosis (CF) patients. Twelve adult CF patients received a single 400-mg dose of IV ciprofloxacin. Six blood samples were obtained over a 12-h interval. Serum drug concentrations were determined by high-pressure liquid chromotography and were fitted to one- and two-compartment models by using NPEM2. Ciprofloxacin MIC data for Pseudomonas aeruginosa were obtained from 1,213 CF patients enrolled in a large clinical trial. A Monte Carlo simulation was performed to estimate the fractional attainment of an AUC0–24/MIC ratio of ≥125. A two-compartment model best describes the serum drug concentration data. The mean fitted PK parameter values are volume of distribution in the central compartment, 0.29 liter/kg; volume of distribution at steady state, 1.1 liters/kg; total clearance, 0.34 liter/h/kg; distributional clearance, 0.89 liter/h/kg; half-life at α phase, 0.16 h; and half-life at β phase, 2.9 h. The overall fractional attainment of achieving an AUC0–24/MIC ratio of ≥125 against P. aeruginosa isolates with ciprofloxacin (400 mg every 12 h [q12h] and 8 qh) were 10 and 30%, respectively. A clinical breakpoint MIC of <0.5 μg/ml for susceptibility is suggested, based on an examination of the fractional attainment of the AUC0–24/MIC target at each MIC. The recommended doses of 400 mg q8h or q12h may be inadequate to treat an acute pulmonary exacerbation when given alone. The poor and variable AUC0–24/MIC ratios support the use of TDM to monitor and adjust the dosage to optimize the efficacy of ciprofloxacin therapy in these patients.

scholarly journals In Vitro to In Vivo Extrapolation Linked to Physiologically Based Pharmacokinetic Models for Assessing the Brain Drug Disposition

2022 ◽  
Vol 24 (1) ◽  
Author(s):  
Yukiko Murata ◽  
Sibylle Neuhoff ◽  
Amin Rostami-Hodjegan ◽  
Hiroyuki Takita ◽  
Zubida M. Al-Majdoub ◽  
...  
Keyword(s):  
Species Differences ◽  
Drug Disposition ◽  
Concentration Data ◽  
Pbpk Models ◽  
Physiologically Based Pharmacokinetic ◽  
Drug Concentrations ◽  
Physiologically Based ◽  
The Brain

AbstractDrug development for the central nervous system (CNS) is a complex endeavour with low success rates, as the structural complexity of the brain and specifically the blood-brain barrier (BBB) poses tremendous challenges. Several in vitro brain systems have been evaluated, but the ultimate use of these data in terms of translation to human brain concentration profiles remains to be fully developed. Thus, linking up in vitro-to-in vivo extrapolation (IVIVE) strategies to physiologically based pharmacokinetic (PBPK) models of brain is a useful effort that allows better prediction of drug concentrations in CNS components. Such models may overcome some known aspects of inter-species differences in CNS drug disposition. Required physiological (i.e. systems) parameters in the model are derived from quantitative values in each organ. However, due to the inability to directly measure brain concentrations in humans, compound-specific (drug) parameters are often obtained from in silico or in vitro studies. Such data are translated through IVIVE which could be also applied to preclinical in vivo observations. In such exercises, the limitations of the assays and inter-species differences should be adequately understood in order to verify these predictions with the observed concentration data. This report summarizes the state of IVIVE-PBPK-linked models and discusses shortcomings and areas of further research for better prediction of CNS drug disposition.

scholarly journals Evolution under low antibiotic concentrations: a risk for the selection of Pseudomonas aeruginosa multidrug resistant mutants in nature

2021 ◽  
Author(s):  
Fernando Sanz-García ◽  
Sara Hernando-Amado ◽  
José Luis Martínez
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Antibiotic Resistance ◽  
Polymyxin B ◽  
Multidrug Resistant ◽  
Resistant Bacteria ◽  
Published Data ◽  
Natural Ecosystems ◽  
Clinical Value ◽  
Drug Concentrations ◽  
Resistant Mutants

ABSTRACTBACKGROUNDAntibiotic pollution of non-clinical environments might have a relevant impact on human health if resistant pathogens are selected. However, this potential risk is often overlooked, since drug concentrations in nature are usually below their minimal inhibitory concentrations (MICs). Albeit, antibiotic resistant bacteria can be selected even at sub-MIC concentrations, in a range that is dubbed the sub-MIC selective window, which depends on both the antibiotic and the pathogen.OBJECTIVESDetermine the sub-MIC selective windows of seven antibiotics of clinical relevance in the opportunistic pathogen Pseudomonas aeruginosa and evaluate the risk for selecting resistant mutants in nature, based on published data about the amount of antimicrobials detected in natural environments.METHODSWe conducted evolution experiments of P. aeruginosa PA14 in presence of sub-MIC concentrations of ceftazidime, amikacin, levofloxacin, ciprofloxacin, tetracycline, polymyxin B or imipenem, and measured drug susceptibility of the evolved populations.RESULTSSub-MIC selective window of quinolones was the largest, and the ones of polymyxin B and imipenem, the narrowest. Clinically relevant multidrug resistant (MDR) mutants (presenting MICs above EUCAST clinical breakpoints) arose within the sub-MIC selective windows of the majority of antibiotics tested, being these phenotypes probably mediated by efflux pumps′ activity.DISCUSSIONOur data show that the concentration of antibiotics reported in aquatic ecosystems -colonizable by P. aeruginosa- are, in occasions, higher than the ones able to select MDR mutants. This finding has implications for understanding the role of different ecosystems and conditions in the emergence of antibiotic resistance from a One-Health point of view. Further, it highlights the importance of delineating the sub-MIC selective windows for drugs of clinical value in pathogens with environmental niches, in order to evaluate the health risks due to antibiotic pollution of natural ecosystems and ultimately tackle antibiotic resistance.

scholarly journals O20 Dose-linearity of the pharmacokinetics of an intravenous [14C]midazolam microdose in children

2019 ◽  
Vol 104 (6) ◽  
pp. e9.1-e9
Author(s):  
BD van Groen ◽  
WHJ Vaes ◽  
BK Park ◽  
EHJ Krekels ◽  
E van Duijn ◽  
...  
Keyword(s):  
Drug Disposition ◽  
Plasma Concentrations ◽  
Volume Of Distribution ◽  
Developmental Changes ◽  
Developmentally Regulated ◽  
Age Related ◽  
Dose Linearity ◽  
Significant Difference ◽  
Therapeutic Doses ◽  
Cyp3a Enzyme

BackgroundDrug disposition in children may vary from adults due to age-related variation in drug metabolism, but paediatric pharmacokinetic (PK) studies are challenging. Microdose studies present an innovation to study PK in paediatrics, and can only be used when the PK of a microdose are dose-linear to a therapeutic dose. We aimed to assess dose-linearity of [14C]midazolam (MDZ), a marker for the activity of the developmentally regulated CYP3A enzyme, by comparing the PK of an intravenous (IV) [14C]MDZ microtracer given simultaneously with therapeutic MDZ, with the PK of a single IV [14C]MDZ microdose.MethodsPreterm to 2-year-old infants admitted to the intensive care unit received [14C]MDZ IV either as a microtracer during therapeutic MDZ infusion or as an isolated microdose. Dense blood sampling was done up to 36 hours after dosing. Plasma concentrations of [14C]MDZ and [14C]1-OH-MDZ were determined by accelerator mass spectrometry. A population PK model was developed with NONMEM 7.4 to study whether there was a difference in the PK of the microtracer versus those of a microdose [14C]MDZ.ResultsOf fifteen children (median gestational age 39.4 [range 23.9–41.4] weeks, postnatal age 11.4 [0.6–49.1] weeks), nine received a microdose and six a microtracer [14C]MDZ (111 Bq/kg; 37.6 ng/kg). In a two-compartment PK model, bodyweight was the most significant covariate for volume of distribution. There was no statistically significant difference in any PK parameter between the [14C]MDZ microdose or microtracer, suggesting the PK of MDZ to be linear within the range of the therapeutic doses and microdoses.ConclusionOur data supports the dose-linearity of an IV [14C]MDZ microdose in children, thus a [14C]MDZ microdosing approach can be used to study developmental changes in hepatic CYP3A activity.Disclosure(s)This project was funded by the ZonMw ERA-NET PRIOMEDCHILD programme (projectnumber 113205022). * both authors contributed equally

scholarly journals Population Pharmacokinetics of Cycloserine and Pharmacokinetic/Pharmacodynamic Target Attainment in Multidrug-Resistant Tuberculosis Patients Dosed with Terizidone

2020 ◽  
Vol 64 (11) ◽  
Author(s):  
Maxwell T. Chirehwa ◽  
Richard Court ◽  
Mariana de Kock ◽  
Lubbe Wiesner ◽  
Nihal de Vries ◽  
...  
Keyword(s):  
Population Pharmacokinetics ◽  
Multidrug Resistant ◽  
Volume Of Distribution ◽  
Fat Free Mass ◽  
Development Of Resistance ◽  
Resistant Tuberculosis ◽  
Multidrug Resistant Tuberculosis ◽  
Group B ◽  
Disposition Model

ABSTRACT Cycloserine is a WHO group B drug for the treatment of multidrug-resistant tuberculosis (TB). Pharmacokinetic/pharmacodynamic data for cycloserine when dosed as terizidone are sparse. The aim of this analysis was to describe the population pharmacokinetics of cycloserine when administered as terizidone and predict the doses of terizidone attaining cycloserine exposures associated with efficacy. The plasma cycloserine level was measured 2 to 6 weeks after treatment initiation in patients hospitalized for second-line tuberculosis treatment. The pretreatment MICs of cycloserine were determined for the clinical isolates. We enrolled 132 participants with rifampicin-resistant TB; 79 were HIV positive. The median pretreatment MIC was 16 mg/liter. A one-compartment disposition model with two clearance pathways, nonrenal (0.35 liters/h) and renal (0.43 liters/h), described cycloserine pharmacokinetics well. Nonrenal clearance and the volume of distribution were allometrically scaled using fat-free mass. Smoking increased nonrenal clearance by 41%. Simulations showed that with daily doses of terizidone (750 mg and 1,000 mg for patients weighing ≤45 kg and >45 kg, respectively), the probability of maintaining the plasma cycloserine concentration above the MIC for more than 30% of the dosing interval (30% T>MIC) (which is associated with a 1.0-log10-CFU/ml kill in vitro) exceeded 90% at MIC values of ≤16 mg/liter, but the proportion of patients achieving 100% T>MIC (which is associated with the prevention of resistance) was more than 90% only at MICs of ≤8 mg/liter. Based on a target derived in vitro, the WHO-recommended doses of terizidone are effective for cycloserine MICs of ≤8 mg/liter, and higher doses are required to prevent the development of resistance.

Effect of Modified Hydroxypropyl Tapioca Starch and Percentage of Drug Loading on Physical Property of Paracetamol Tablet

2020 ◽  
Vol 859 ◽  
pp. 3-8
Author(s):  
Vipaluk Patomchaiviwat ◽  
Sontaya Limmatvapirat ◽  
Chaisai Sirisapaya ◽  
Rohanee Kolae ◽  
Kulmanee Anantakul ◽  
...  
Keyword(s):  
Drug Loading ◽  
Physical Property ◽  
High Hardness ◽  
Direct Compression ◽  
Compression Method ◽  
Disintegration Time ◽  
Tapioca Starch ◽  
Drug Concentrations ◽  
Model Drug ◽  
Better Than

The objective of this study was to investigate the effect of modified hydroxypropyl tapioca starch (HPTS) and % drug loading on physical property of tablet. Paracetamol was used as model drug because of its poor compressibility. The filler ability of modified HPTS such as hydroxyl propyl oxidized tapioca starch (HPOTS), hydroxyl propyl crosslinked tapioca starch (HPCTS) and pregelatinized tapioca starch (PTS) were evaluated and compared with the commercial starch (Starch 1500®). Tablets were prepared by direct compression method and the percent drug loading were 15, 30, 45, 60, 75%. For modified HPTS, the hardness of the tablets tended to decrease when the concentration of paracetamol increased. At drug concentrations of 15-30%, HPOTS exhibited good performance of tablet as indicated by the high hardness, low friability and acceptable disintegration time. The obtained results were better than HPTS and comparable to Starch 1500®. Moreover, the results revealed that tablet containing PTS provided the highest hardness and prolonged disintegration time (>30 min) while tablet containing HPCTS showed rapid disintegration time (<2 min). Therefore, modified HPTS disclosed promising properties for application as tablet filler

Altered pHi regulation in 3T3/CFTR clones and their chemotherapeutic drug-selected derivatives

1997 ◽  
Vol 272 (5) ◽  
pp. C1642-C1653 ◽  
Author(s):  
L. Y. Wei ◽  
M. M. Hoffman ◽  
P. D. Roepe
Keyword(s):  
Drug Resistance ◽  
Multidrug Resistant ◽  
Mrna Levels ◽  
Chemotherapeutic Drug ◽  
Drug Concentrations ◽  
Nih 3T3 ◽  
Incremental Step ◽  
Mdr 1 ◽  
Phi Regulation ◽  
Exchange Activity

Recently (L. Y. Wei, M. J. Stutts, M. M. Hoffman, and P. D. Roepe. Biophys. J. 69: 883-895, 1996), 3T3 cells overexpressing the cystic fibrosis transmembrane conductance regulator (CFTR) were found to exhibit chemotherapeutic drug resistance and other traits of multidrug resistant (MDR) cells. In the present work, NIH 3T3/CFTR clones were selected with either doxorubicin or vincristine in incremental fashion to generate series of stable MDR cell lines that exhibit increasing levels of drug resistance. Thus C3D6 (grown in the presence of 600 nM doxorubicin) was selected from C3D4 (grown in the presence of 400 nM doxorubicin), which was selected from C3D1 (grown in the presence of 100 nM doxorubicin), which was in turn selected from the original 3T3/CFTR clone C3 (M. J. Stutts, S. E. Gabriel, J. C. Olsen, J. T. Gatzy, T. L. O'Connell, E. M. Price, and R. C. Boucher. J. Biol. Chem. 268: 20653-20658, 1993), which was not grown in the presence of chemotherapeutic drug. A similar series was generated via selection with vincristine. In both series, as well as series derived from a different CFTR clone, initial low-level drug selection increases CFTR expression without promoting MDR 1 or multidrug resistance-associated protein expression. On continued selection at higher drug concentrations, CFTR mRNA levels decrease while MDR 1 mRNA levels concomitantly increase. At each incremental step of selection, intracellular pH (pHi) increases (e.g., pHi of C3D6 > C3D4 > C3D1 > C3). Cl-/HCO3- exchange activity is significantly reduced in the drug-selected derivatives overexpressing MDR 1 but not the parental CFTR clones. The apparent set point of Na+/H+ exchange activity is significantly lower for the non-drug-selected 3T3/CFTR clones, relative to controls, but it increases on initial selection with chemotherapeutic drug. Overexpression of MDR 1 in the higher-level selectants does not appear to further perturb apparent Na+/H+ exchange. These data further describe how CFTR and MDR proteins may affect pHi regulation.

scholarly journals Population Pharmacokinetics and Dosing of Ethionamide in Children with Tuberculosis

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Henrik Bjugård Nyberg ◽  
Heather R. Draper ◽  
Anthony J. Garcia-Prats ◽  
Stephanie Thee ◽  
Adrie Bekker ◽  
...  
Keyword(s):  
Drug Exposure ◽  
Multidrug Resistant ◽  
Volume Of Distribution ◽  
Pharmacokinetic Parameters ◽  
Limited Information ◽  
Once Daily ◽  
Content Type ◽  
Mixed Effects Modeling ◽  
Hiv Coinfection ◽  
Antituberculosis Treatment

ABSTRACT Ethionamide has proven efficacy against both drug-susceptible and some drug-resistant strains of Mycobacterium tuberculosis. Limited information on its pharmacokinetics in children is available, and current doses are extrapolated from weight-based adult doses. Pediatric doses based on more robust evidence are expected to improve antituberculosis treatment, especially in small children. In this analysis, ethionamide concentrations in children from 2 observational clinical studies conducted in Cape Town, South Africa, were pooled. All children received ethionamide once daily at a weight-based dose of approximately 20 mg/kg of body weight (range, 10.4 to 25.3 mg/kg) in combination with other first- or second-line antituberculosis medications and with antiretroviral therapy in cases of HIV coinfection. Pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling. The MDR-PK1 study contributed data for 110 children on treatment for multidrug-resistant tuberculosis, while the DATiC study contributed data for 9 children treated for drug-susceptible tuberculosis. The median age of the children in the studies combined was 2.6 years (range, 0.23 to 15 years), and the median weight was 12.5 kg (range, 2.5 to 66 kg). A one-compartment, transit absorption model with first-order elimination best described ethionamide pharmacokinetics in children. Allometric scaling of clearance (typical value, 8.88 liters/h), the volume of distribution (typical value, 21.4 liters), and maturation of clearance and absorption improved the model fit. HIV coinfection decreased the ethionamide bioavailability by 22%, rifampin coadministration increased clearance by 16%, and ethionamide administration by use of a nasogastric tube increased the rate, but the not extent, of absorption. The developed model was used to predict pediatric doses achieving the same drug exposure achieved in 50- to 70-kg adults receiving 750-mg once-daily dosing. Based on model predictions, we recommend a weight-banded pediatric dosing scheme using scored 125-mg tablets.

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