scholarly journals Pharmacokinetics-Pharmacodynamics of Rifampin in an Aerosol Infection Model of Tuberculosis

2003 ◽  
Vol 47 (7) ◽  
pp. 2118-2124 ◽  
Author(s):  
Ramesh Jayaram ◽  
Sheshagiri Gaonkar ◽  
Parvinder Kaur ◽  
B. L. Suresh ◽  
B. N. Mahesh ◽  
...  
Keyword(s):  
Equilibrium Dialysis ◽  
Exposure Period ◽  
Dose Fractionation ◽  
Infection Model ◽  
Limited Information ◽  
Time Curve ◽  
Free System ◽  
Aerosol Infection ◽  
Time Kill

ABSTRACT Limited information exists on the pharmacokinetic (PK)-pharmacodynamic (PD) relationships of drugs against Mycobacterium tuberculosis. Our aim was to identify the PK-PD parameter that best describes the efficacy of rifampin on the basis of in vitro and PK properties. Consistent with 83.8% protein binding by equilibrium dialysis, the rifampin MIC for M. tuberculosis strain H37Rv rose from 0.1 in a serum-free system to 1.0 mg/ml when it was tested in the presence of 50% serum. In time-kill studies, rifampin exhibited area under the concentration-time curve (AUC)-dependent killing in vitro, with maximal killing seen on all days and with the potency increasing steadily over a 9-day exposure period. MIC and time-kill studies performed with intracellular organisms in a macrophage monolayer model yielded similar results. By use of a murine aerosol infection model with dose ranging and dose fractionation over 6 days, the PD parameter that best correlated with a reduction in bacterial counts was found to be AUC/MIC (r 2 = 0.95), whereas the maximum concentration in serum/MIC (r 2 = 0.86) and the time that the concentration remained above the MIC (r 2 = 0.44) showed lesser degrees of correlation.

scholarly journals Isoniazid Pharmacokinetics-Pharmacodynamics in an Aerosol Infection Model of Tuberculosis

2004 ◽  
Vol 48 (8) ◽  
pp. 2951-2957 ◽  
Author(s):  
Ramesh Jayaram ◽  
Radha. K. Shandil ◽  
Sheshagiri Gaonkar ◽  
Parvinder Kaur ◽  
B. L. Suresh ◽  
...  
Keyword(s):  
Dose Fractionation ◽  
Maximum Effect ◽  
Infection Model ◽  
Limited Data ◽  
Time Curve ◽  
Bactericidal Efficacy ◽  
Infection Models ◽  
Bactericidal Activities ◽  
Aerosol Infection

ABSTRACT Limited data exist on the pharmacokinetic-pharmacodynamic (PK-PD) parameters of the bactericidal activities of the available antimycobacterial drugs. We report on the PK-PD relationships for isoniazid. Isoniazid exhibited concentration (C)-dependent killing of Mycobacterium tuberculosis H37Rv in vitro, with a maximum reduction of 4 log10 CFU/ml. In these studies, 50% of the maximum effect was achieved at a C/MIC ratio of 0.5, and the maximum effect did not increase with exposure times of up to 21 days. Conversely, isoniazid produced less than a 0.5-log10 CFU/ml reduction in two different intracellular infection models (J774A.1 murine macrophages and whole human blood). In a murine model of aerosol infection, isoniazid therapy for 6 days produced a reduction of 1.4 log10 CFU/lung. Dose fractionation studies demonstrated that the 24-h area under the concentration-time curve/MIC (r 2 = 0.83) correlated best with the bactericidal efficacy, followed by the maximum concentration of drug in serum/MIC (r 2 = 0.73).

scholarly journals 682. In Vivo Pharmacodynamics of VNRX-7145 in the Neutropenic Murine Thigh Infection Model When Administered in Combination with Humanized Exposures of Twice Daily Ceftibuten (CTB) Against Serine β-Lactamase-Producing Enterobacteriaceae (SBL-EB)

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S311-S311 ◽  
Author(s):  
Lindsay M Avery ◽  
Kamilia Abdelraouf ◽  
David P Nicolau
Keyword(s):  
Complicated Urinary Tract Infection ◽  
Dose Fractionation ◽  
Intrinsic Activity ◽  
Infection Model ◽  
Bacterial Burden ◽  
Dose Ratio ◽  
Time Curve ◽  
In Vitro Susceptibility

Abstract Background There is a pressing need for development of oral antibiotics with activity against SBL-EB, particularly carbapenemase-producers, for use in the community or as step-down therapy for complicated urinary tract infection. VNRX-7145 is a novel boronic acid-based SBL inhibitor with no intrinsic activity that was designed as an orally bioavailable prodrug. The active moiety (VNRX-5236) is known to restore in vitro susceptibility to (CTB), an oral cephalosporin, among CTB-resistant SBL-EB. Methods CTB-resistant SBL-EB (N = 21) with CTB MICs ≥32 µg/mL and CTB/VNRX-5236 MIC range 0.12–2 µg/mL (VNRX-5236 fixed at 4 µg/mL) were evaluated. Carbapenemases were produced by 9 strains (4 OXA, 5 KPC). Bacterial suspensions (~107 CFU/mL) were used to inoculate the thighs of neutropenic mice. A human-simulated regimen of ceftibuten (CTB HSR) equivalent to a 400 mg q12h dosage was developed in infected mice. In dose ranging studies, groups of 3 animals each received the CTB HSR as monotherapy or combined with escalating VNRX-5236 exposures (CTB:VNRX-5236 dose ratios ranging from 10:1 to 1:4). Efficacy was assessed as the change in log10 CFU/thigh at 24 hours from 0 hour burden. With previous in vivo dose fractionation studies indicating the free area under the VNRX-5236 concentration–time curve to MIC ratio (fAUC0-24/MIC) as the PK/PD driver of efficacy, the Hill equation was used to estimate the magnitude required to achieve a static endpoint. Results Compared with 0 hour controls (mean log10 CFU/thigh, 5.7 ± 0.3), the bacterial burden for all isolates increased in saline-dosed controls and CTB HSR groups by 3.1 ± 0.8 and 2.5 ± 0.8 log10 CFU/thigh, respectively. The addition of VNRX-5236 resulted in bacterial stasis in 20/21 strains; the mean reduction in bacterial burden with the 1:1 CTB:VNRX-5236 dose ratio was −0.2 ± 0.7 log10 CFU/thigh. A composite assessment of exposure-responses indicated a fAUC0-24/MIC of 9.0 (R2 = 0.70) was associated with stasis. Conclusion Against CTB-resistant SBL-EB, inclusive of OXA-48- and KPC-producing strains, VNRX-5236 potentiated the in vivo activity of the CTB human-simulated exposure. The identified fAUC0-24/MIC target associated with bacterial stasis should be considered when selecting VNRX-7145 doses for clinical studies. Disclosures All authors: No reported disclosures.

scholarly journals In VivoPharmacodynamics of Torezolid Phosphate (TR-701), a New Oxazolidinone Antibiotic, against Methicillin-Susceptible and Methicillin-Resistant Staphylococcus aureus Strains in a Mouse Thigh Infection Model

2011 ◽  
Vol 55 (7) ◽  
pp. 3453-3460 ◽  
Author(s):  
Arnold Louie ◽  
Weiguo Liu ◽  
Robert Kulawy ◽  
G. L. Drusano
Keyword(s):  
Staphylococcus Aureus ◽  
Dose Range ◽  
Dose Fractionation ◽  
Infection Model ◽  
Pharmacokinetic Studies ◽  
Time Curve ◽  
Methicillin Resistant ◽  
Content Type

ABSTRACTTorezolid phosphate (TR-701) is the phosphate monoester prodrug of the oxazolidinone TR-700 which demonstrates potentin vitroactivity against Gram-positive bacteria, including methicillin-susceptibleStaphylococcus aureus(MSSA) and methicillin-resistantS. aureus(MRSA). The pharmacodynamics of TR-701 or TR-700 (TR-701/700) againstS. aureusis incompletely defined. Single-dose pharmacokinetic studies were conducted in mice for TR-701/700. Forty-eight-hour dose range and 24-hour dose fractionation studies were conducted in a neutropenic mouse thigh model ofS. aureusinfection using MRSA ATCC 33591 to identify the dose and schedule of administration of TR-701/700 that was linked with optimized antimicrobial effect. Additional dose range studies compared the efficacies of TR-701/700 and linezolid for one MSSA strain and one community-associated MRSA strain. In dose range studies, TR-701/700 was equally bactericidal against MSSA and MRSA. Mean doses of 37.6 and 66.9 mg/kg of body weight/day of TR-701/700 resulted in stasis and 1 log CFU/g decreases in bacterial densities, respectively, at 24 h, and mean doses of 35.3, 46.6, and 71.1 mg/kg/day resulted in stasis and 1 and 2 log CFU/g reductions, respectively, at 48 h. Linezolid administered at doses as high as 150 mg/kg/day did not achieve stasis at either time point. Dose fractionation studies demonstrated that the area under the concentration-time curve over 24 h in the steady state divided by the MIC (AUC/MIC ratio) was the pharmacodynamic index for TR-701/700 that was linked with efficacy. TR-701/700 was highly active against MSSA and MRSA,in vivo, and was substantially more efficacious than linezolid, although linezolid's top exposure has half the human exposure. Dose fractionation studies showed that AUC/MIC was the pharmacodynamic index linked with efficacy, indicating that once-daily dosing in humans is feasible.

scholarly journals Pharmacokinetics-Pharmacodynamics of a Novel β-Lactamase Inhibitor, CB-618, in Combination with Meropenem in anIn VitroInfection Model

2016 ◽  
Vol 60 (7) ◽  
pp. 3891-3896 ◽  
Author(s):  
Brian D. VanScoy ◽  
Michael Trang ◽  
Jennifer McCauley ◽  
Haley Conde ◽  
Sujata M. Bhavnani ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Dose Fractionation ◽  
Infection Model ◽  
Time Curve ◽  
Content Type ◽  
Concentration Time ◽  
Wide Range ◽  
Dosing Regimens ◽  
Lactamase Inhibitor

ABSTRACTThe usefulness of β-lactam antimicrobial agents is threatened as never before by β-lactamase-producing bacteria. For this reason, there has been renewed interest in the development of broad-spectrum β-lactamase inhibitors. Herein we describe the results of dose fractionation and dose-ranging studies carried out using a one-compartmentin vitroinfection model to determine the exposure measure for CB-618, a novel β-lactamase inhibitor, most predictive of the efficacy when given in combination with meropenem. The challenge panel includedEnterobacteriaceaeclinical isolates, which collectively produced a wide range of β-lactamase enzymes (KPC-2, KPC-3, FOX-5, OXA-48, SHV-11, SHV-27, and TEM-1). Human concentration-time profiles were simulated for each drug, and samples were collected for drug concentration and bacterial density determinations. Using data from dose fractionation studies and a challengeKlebsiella pneumoniaeisolate (CB-618-potentiated meropenem MIC = 1 mg/liter), relationships between change from baseline in log10CFU/ml at 24 h and each of CB-618 area under the concentration-time curve over 24 h (AUC0–24), maximum concentration (Cmax), and percentage of the dosing interval that CB-618 concentrations remained above a given threshold were evaluated in combination with meropenem at 2 g every 8 h (q8h). The exposure measures most closely associated with CB-618 efficacy in combination with meropenem were the CB-618 AUC0–24(r2= 0.835) andCmax(r2= 0.826). Using the CB-618 AUC0–24indexed to the CB-618-potentiated meropenem MIC value, the relationship between change from baseline in log10CFU/ml at 24 h and CB-618 AUC0–24/MIC ratio in combination with meropenem was evaluated using the pooled data from five challenge isolates; the CB-618 AUC0–24/MIC ratio associated with net bacterial stasis and the 1- and 2-log10CFU/ml reductions from baseline at 24 h were 27.3, 86.1, and 444.8, respectively. These data provide a pharmacokinetics-pharmacodynamics (PK-PD) basis for evaluating potential CB-618 dosing regimens in combination with meropenem in future studies.

scholarly journals Pharmacodynamics of Daptomycin in a Murine Thigh Model of Staphylococcus aureus Infection

2001 ◽  
Vol 45 (3) ◽  
pp. 845-851 ◽  
Author(s):  
Arnold Louie ◽  
Pamela Kaw ◽  
Weiguo Liu ◽  
Nelson Jumbe ◽  
Michael H. Miller ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Single Dose ◽  
Dose Fractionation ◽  
Mouse Serum ◽  
Maximum Effect ◽  
Infection Model ◽  
Pharmacokinetic Studies ◽  
Time Curve ◽  
Dose Response Effect

ABSTRACT Daptomycin is a lipopeptide antibiotic with activity against gram-positive bacteria, including Staphylococcus aureus. We defined the pharmacodynamic parameters that determine the activity of daptomycin for S. aureus using in vitro methods and the Craig (W. A. Craig, J. Redington, and S. C. Ebert, J. Antimicrob. Chemother. 27[Suppl. C]:29–40, 1991) neutropenic mouse thigh infection model. In Mueller-Hinton broth, the MICs for threeS. aureus isolates were 0.1 to 0.2 μg/ml. In mouse serum, the MICs were 1.0 μg/ml. The protein binding of daptomycin was 90 to 92.5% in mouse serum. Single-dose intraperitoneal (i.p.) pharmacokinetic studies with infected mice showed a linear relationship between dose versus the maximum concentration of drug in serum and dose versus the area under the concentration-time curve (AUC). The serum half-life of daptomycin in infected mice was approximately 1.8 h. In single-dose, dose-ranging studies using mice, daptomycin showed a dose-response effect described by an inhibitory sigmoidE max (maximum effect) curve (r = 0.974; P ≪ 0.001). The density of S. aureus in untreated controls was 8.26 log10 CFU/g, and the E max was 3.97 log10 CFU/g. The 50% effective dose (ED50) was 3.7 mg/kg of body weight i.p. and the stasis dose was 7.1 mg/kg. Dose fractionation studies at schedules of Q6h, Q12h, and Q24h, for total 24-h ED30, ED60, and ED80 doses of 2.5, 5.6, and 15 mg/kg i.p., showed no difference in effect at each total 24-h dose level by schedule, indicating that the AUC/MIC ratio is the dynamically linked variable.

scholarly journals Evaluation of Once-Daily Vancomycin against Methicillin-Resistant Staphylococcus aureus in a Hollow-Fiber Infection Model

2011 ◽  
Vol 56 (2) ◽  
pp. 682-686 ◽  
Author(s):  
Anthony M. Nicasio ◽  
Jürgen B. Bulitta ◽  
Thomas P. Lodise ◽  
Rebecca E. D'Hondt ◽  
Robert Kulawy ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Hollow Fiber ◽  
Daily Administration ◽  
Dose Fractionation ◽  
Infection Model ◽  
Time Curve ◽  
Once Daily ◽  
Methicillin Resistant ◽  
Content Type

ABSTRACTFor methicillin-resistantStaphylococcus aureus(MRSA) infections, data suggest that the clinical response is significantly better if the total vancomycin area under the concentration-time curve (AUC)/MIC ratio is ≥400. While the AUC/MIC ratio is the accepted pharmacokinetic/pharmacodynamic (PK/PD) index for vancomycin, this target has been achieved using multiple daily doses. We are unaware of a systematically designed dose fractionation study to compare the bactericidal activity of once-daily administration to that of traditional twice-daily administration. A dose fractionation study was performed with vancomycin in anin vitrohollow-fiber infection model against an MRSA USA300 strain (MIC of 0.75 μg/ml) using an inoculum of ∼106CFU/ml. The three vancomycin regimens evaluated for 168 h were 2 g every 24 h (q24h) as a 1-h infusion, 1 g q12h as a 1-h infusion, and 2 g q24h as a continuous infusion. Free steady-state concentrations (assuming 45% binding) for a total daily AUC/MIC ratio of ≥400 were simulated for all regimens. A validated liquid chromatography-tandem mass spectrometry method was used to determine vancomycin concentrations. Although once-daily and twice-daily dosage regimens exhibited total trough concentrations of <15 μg/ml, all regimens achieved similar bactericidal activities between 24 and 168 h and suppressed the amplification of nonsusceptible subpopulations. No colonies were found on agar plates with 3× MIC for any of the treatment arms. Overall, the results suggest that once-daily vancomycin administration is feasible from a PK/PD perspective and merits further inquiry in the clinical arena.

scholarly journals Pharmacokinetic-Pharmacodynamic Evaluation of Gepotidacin against Gram-Positive Organisms Using Data from Murine Infection Models

2016 ◽  
Vol 61 (2) ◽  
Author(s):  
Catharine C. Bulik ◽  
Ólanrewaju O. Okusanya ◽  
Elizabeth A. Lakota ◽  
Alan Forrest ◽  
Sujata M. Bhavnani ◽  
...  
Keyword(s):  
Lung Infection ◽  
Free Drug ◽  
Dose Fractionation ◽  
Infection Model ◽  
Time Curve ◽  
Content Type ◽  
Drug Plasma ◽  
Infection Models

ABSTRACT Gepotidacin (formerly called GSK2140944) is a novel triazaacenaphthylene bacterial topoisomerase inhibitor with in vitro activity against conventional and biothreat pathogens, including Staphylococcus aureus and Streptococcus pneumoniae. Using neutropenic murine thigh and lung infection models, the pharmacokinetics-pharmacodynamics (PK-PD) of gepotidacin against S. aureus and S. pneumoniae were characterized. Candidate models were fit to single-dose PK data from uninfected mice (for doses of 16 to 128 mg/kg of body weight given subcutaneously [s.c.]). Dose fractionation studies (1 isolate/organism; 2 to 512 mg/kg/day) and dose-ranging studies (5 isolates/organism; 2 to 2,048 mg/kg/day; MIC ranges of 0.5 to 2 mg/liter for S. aureus and 0.125 to 1 mg/liter for S. pneumoniae) were conducted. The presence of an in vivo postantibiotic effect (PAE) was also evaluated. Relationships between the change from baseline in log10 CFU at 24 h and the ratio of the free-drug plasma area under the concentration-time curve (AUC) to the MIC (AUC/MIC ratio), the ratio of the maximum concentration of drug in plasma (C max) to the MIC (C max/MIC ratio), and the percentage of a 24-h period that the drug concentration exceeded the MIC (%T>MIC) were evaluated using Hill-type models. Plasma and epithelial lining fluid (ELF) PK data were best fit by a four-compartment model with linear distributional clearances, a capacity-limited clearance, and a first-order absorption rate. The ELF penetration ratio in uninfected mice was 0.65. Since the growth of both organisms was poor in the murine lung infection model, lung efficacy data were not reported. As determined using the murine thigh infection model, the free-drug plasma AUC/MIC ratio was the PK-PD index most closely associated with efficacy (r 2 = 0.936 and 0.897 for S. aureus and S. pneumoniae, respectively). Median free-drug plasma AUC/MIC ratios of 13.4 and 58.9 for S. aureus, and 7.86 and 16.9 for S. pneumoniae, were associated with net bacterial stasis and a 1-log10 CFU reduction from baseline, respectively. Dose-independent PAE durations of 3.07 to 12.5 h and 5.25 to 8.46 h were demonstrated for S. aureus and S. pneumoniae, respectively.

scholarly journals Exploring the Pharmacokinetic/Pharmacodynamic Relationship of Relebactam (MK-7655) in Combination with Imipenem in a Hollow-Fiber Infection Model

2018 ◽  
Vol 62 (5) ◽  
Author(s):  
Jin Wu ◽  
Fred Racine ◽  
Michael K. Wismer ◽  
Katherine Young ◽  
Donna M. Carr ◽  
...  
Keyword(s):  
Hollow Fiber ◽  
Bacterial Infections ◽  
New Drugs ◽  
Dose Fractionation ◽  
Resistant Bacteria ◽  
Infection Model ◽  
Time Curve ◽  
Content Type ◽  
Relationship Of

ABSTRACT Resistance to antibiotics among bacterial pathogens is rapidly spreading, and therapeutic options against multidrug-resistant bacteria are limited. There is an urgent need for new drugs, especially those that can circumvent the broad array of resistance pathways that bacteria have evolved. In this study, we assessed the pharmacokinetic/pharmacodynamic relationship of the novel β-lactamase inhibitor relebactam (REL; MK-7655) in a hollow-fiber infection model. REL is intended for use with the carbapenem β-lactam antibiotic imipenem for the treatment of Gram-negative bacterial infections. In this study, we used an in vitro hollow-fiber infection model to confirm the efficacy of human exposures associated with the phase 2 doses (imipenem at 500 mg plus REL at 125 or 250 mg administered intravenously every 6 h as a 30-min infusion) against imipenem-resistant strains of Pseudomonas aeruginosa and Klebsiella pneumoniae . Dose fractionation experiments confirmed that the pharmacokinetic parameter that best correlated with REL activity is the area under the concentration-time curve, consistent with findings in a murine pharmacokinetic/pharmacodynamic model. Determination of the pharmacokinetic/pharmacodynamic relationship between β-lactam antibiotics and β-lactamase inhibitors is complex, as there is an interdependence between their respective exposure-response relationships. Here, we show that this interdependence could be captured by treating the MIC of imipenem as dynamic: it changes with time, and this change is directly related to REL levels. For the strains tested, the percentage of the dosing interval time that the concentration remains above the dynamic MIC for imipenem was maintained at the carbapenem target of 30 to 40%, required for maximum efficacy, for imipenem at 500 mg plus REL at 250 mg.

scholarly journals Gepotidacin Pharmacokinetics-Pharmacodynamics Against Escherichia coli in the One-Compartment and Hollow-Fiber In Vitro Infection Model Systems

2021 ◽  
Author(s):  
Brian D. VanScoy ◽  
Elizabeth A. Lakota ◽  
Haley Conde ◽  
Steven Fikes ◽  
Sujata M. Bhavnani ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Hollow Fiber ◽  
Free Drug ◽  
Model Systems ◽  
Dose Fractionation ◽  
Infection Model ◽  
Bacterial Reduction ◽  
Time Curve ◽  
E Coli

Gepotidacin is a novel, first-in-class triazaacenaphthylene antibiotic that inhibits bacterial DNA replication by a distinct mechanism of action with an in vitro spectrum of activity that includes Escherichia coli . Our objectives herein were the following: 1) to identify the pharmacokinetic-pharmacodynamics (PK-PD) index associated with efficacy for gepotidacin against E. coli ; 2) to determine the magnitude of the above-described PK-PD index associated with various bacterial reduction endpoints for E. coli ; and 3) to characterize the relationship between gepotidacin exposure and on-therapy E. coli resistance amplification. A 24-hour one-compartment in vitro infection model was used to investigate the first two study objectives and a 10-day hollow-fiber in vitro infection model was used to evaluate the third objective. For the dose-fractionation studies (objective 1), in which E. coli NCTC 13441 (gepotidacin MIC, 2 mg/L) was evaluated, free-drug gepotidacin area under the concentration-time curve (AUC) from 0 to 24 h to the MIC (AUC/MIC ratio) was identified as PK-PD index most closely associated with change in bacterial burden ( R 2 = 0.925). For the dose-ranging studies (objective 2), in which four E. coli isolates (gepotidacin MIC range, 1 to 4 mg/L) were studied, the magnitude of the median free-drug gepotidacin AUC/MIC ratio associated with net bacterial stasis and 1- and 2-log 10 CFU reductions for the pooled dataset was 33.9, 43.7, and 60.7, respectively. For the hollow-fiber in vitro infection model studies (objective 3), in which one isolate ( E. coli NCTC 13441 gepotidacin MIC, 2 mg/L) was evaluated, free-drug gepotidacin AUC/MIC ratios 275 and greater were sufficient to suppress on-therapy resistance amplification. Together, the data generated from these studies will be useful to support discrimination among candidate dosing regimens for future clinical study.

scholarly journals Moxifloxacin, Ofloxacin, Sparfloxacin, and Ciprofloxacin against Mycobacterium tuberculosis: Evaluation of In Vitro and Pharmacodynamic Indices That Best Predict In Vivo Efficacy

2006 ◽  
Vol 51 (2) ◽  
pp. 576-582 ◽  
Author(s):  
Radha K. Shandil ◽  
Ramesh Jayaram ◽  
Parvinder Kaur ◽  
Sheshagiri Gaonkar ◽  
B. L. Suresh ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Rank Order ◽  
Dose Fractionation ◽  
In Vitro Assays ◽  
Infection Model ◽  
Unbound Fraction ◽  
In Vivo Efficacy ◽  
Time Kill

ABSTRACT Members of the fluoroquinolone class are being actively evaluated for inclusion in tuberculosis chemotherapy regimens, and we sought to determine the best in vitro and pharmacodynamic predictors of in vivo efficacy in mice. MICs for Mycobacterium tuberculosis H37Rv were 0.1 mg/liter (sparfloxacin [SPX]) and 0.5 mg/liter (moxifloxacin [MXF], ciprofloxacin [CIP], and ofloxacin [OFX]). The unbound fraction in the presence of murine serum was concentration dependent for MXF, OFX, SPX, and CIP. In vitro time-kill studies revealed a time-dependent effect, with the CFU reduction on day 7 similar for all four drugs. However, with a J774A.1 murine macrophage tuberculosis infection model, CIP was ineffective at up to 32× MIC. In addition, MXF, OFX, and SPX exhibited less activity than had been seen in the in vitro time-kill study. After demonstrating that the area under the concentration-time curve (AUC) and maximum concentration of drug in plasma were proportional to the dose in vivo, dose fractionation studies with total oral doses of 37.5 to 19,200 mg/kg of body weight (MXF), 225 to 115,200 mg/kg (OFX), 30 to 50,000 mg/kg (SPX), and 38 to 100,000 mg/kg (CIP) were performed with a murine aerosol infection model. MXF was the most efficacious agent (3.0 ± 0.2 log10 CFU/lung reduction), followed by SPX (1.4 ± 0.1) and OFX (1.5 ± 0.1). CIP showed no effect. The ratio of the AUC to the MIC was the pharmacodynamic parameter that best described the in vivo efficacy. In summary, a lack of intracellular killing predicted the lack of in vivo activity of CIP. The in vivo rank order for maximal efficacy of the three active fluoroquinolones was not clearly predicted by the in vitro assays, however.

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