Isoniazid Pharmacokinetics-Pharmacodynamics in an Aerosol Infection Model of Tuberculosis

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 log 10 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-log 10 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 log 10 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).No new drugs for the treatment of tuberculosis have been registered in the last 40 years. Discovery of new antimycobacterial agents is in part limited by the laborious and slow nature of the in vitro and in vivo studies required. Knowledge of the pharmacokinetic (PK)-pharmacodynamic (PD) properties of candidate drugs could be used to facilitate drug discovery and evaluation of the effects of combinations of agents. As a step toward such a strategy, we have recently identified the PK-PD parameter that correlated with the in vivo efficacy of rifampin in a murine aerosol model of tuberculosis (7). In the present study, we have extended this work to include isoniazid. MATERIALS AND METHODSReagents. Isoniazid (lot 36H1179) and carboxymethyl cellulose (lot 77H1077) were purchased from Sigma, St. Louis, Mo. Isoniazid stock solutions were prepared in 100% dimethyl sulfoxide (DMSO; Sigma) and diluted in normal saline prior to final use. ETDA (lot 5-4514) was purchased from Hi-Media Labs, Mumbai, India. Acetonitrile (high-pressure liquid chromatography [HPLC] grade) and trichloroacetic acid (TCA) were obtained from Spectrochem Pvt. Ltd., Mumbai, India. Cinnamaldehyde (lot 96320) was obtained from Fluka Biochemika, Bucks, Switzerland.Microbial cultures and cell lines. Mycobacterium tuberculosis H37Rv (ATCC 27294) and J774A.1 macrophages were prepared for in vitro, macrophage, and animal infection studies by previously described methods (7).Blood from healthy volunteers. Group O-positive blood from healthy volunteers collected in citrate phosphate dextrose adenine anticoagulant was obtained from a registered blood bank (TTK Blood Bank, Bangalore, India). It was stored at 4°C and was used for assays up to 1 month from the date of collection.Animals. The Institutional Animal Ethics Committee, registered with the Government of India (registration no. CPCSEA 1999/5), approved all experimental protocols with animals and the use of animals. Ethical practices recommend the use of equal numbers of animals of both sexes w...

Macrophage-Specific Targeting of Isoniazid Through Mannosylated Gelatin Microspheres

“…Another study which, though is not specific to INH, also provided the evidence of metabolic activity of cultured macrophage cells (29). On the other hand, Jayaram et al reported that INH remains stable in macrophage cultures (19). Therefore, data of INH metabolism in uninfected macrophage culture are contradictory and further studies are warranted to explore this aspect.…”

“…The concentration of INH in rat plasma was determined by the method described elsewhere (19), with slight modification. Plasma (50 μl) containing isoniazid was extracted with 100 μl of 10% TCA by vortexing for 30 s. It was then centrifuged (14,000 rpm/10 min).…”

Simultaneous determination of isoniazid and pyrazinamide in plasma by high performance liquid chromatography

“…PZA is particularly effective against the Mycobacterium tuberculosis in the area of necrosis, where acidic media are available. In vitro studies show that both PZA and INH exhibit a concentration-dependent effect [3,4]. Poor patient outcomes were associated with low levels of INH or PZA [5][6][7].…”

Systems Medicine and Infection

“…During this time, progress has also been made in the quantitative description of both pharmacokinetics (PK) and in vitro pharmacodynamics (PD) of antituberculosis drugs [17], [18], [19]. Mathematical models that arise from a systems approach offer a unique potential to establish quantitative links across multiple biological scales.…”