rifampin and pyrazinoic-acid

New therapeutic strategies are needed to treat drug resistant tuberculosis (TB) and to improve treatment for drug sensitive TB. Pyrazinamide (PZA) is a critical component of current first-line TB therapy. However, the rise in PZA-resistant TB cases jeopardizes the future utility of PZA. To address this problem, we used the guinea pig model of TB and tested the efficacy of an inhaled dry powder combination, referred to as Pyrazinoic acid/ester Dry Powder (PDP), which is comprised of pyrazinoic acid (POA), the active moiety of PZA, and pyrazinoic acid ester (PAE), which is a PZA analog. Both POA and PAE have the advantage of being able to act on PZA-resistant Mycobacterium tuberculosis. When used in combination with oral rifampicin (R), inhaled PDP had striking effects on tissue pathology. Effects were observed in lungs, the site of delivery, but also in the spleen and liver indicating both local and systemic effects of inhaled PDP. Tissue granulomas that harbor M. tuberculosis in a persistent state are a hallmark of TB and they pose a challenge for therapy. Compared to other treatments, which preferentially cleared non-necrotic granulomas, R+PDP reduced necrotic granulomas more effectively. The increased ability of R+PDP to act on more recalcitrant necrotic granulomas suggests a novel mechanism of action. The results presented in this report reveal the potential for developing therapies involving POA that are optimized to target necrotic as well as non-necrotic granulomas as a means of achieving more complete sterilization of M. tuberculosis bacilli and preventing disease relapse when therapy ends.

Topics: Aerosols; Animals; Antitubercular Agents; Bacterial Load; Disease Models, Animal; Drug Therapy, Combination; Dry Powder Inhalers; Granuloma, Respiratory Tract; Guinea Pigs; Male; Mycobacterium tuberculosis; Necrosis; Pyrazinamide; Respiratory Tract Absorption; Rifampin; Tuberculosis, Multidrug-Resistant; Tuberculosis, Pulmonary

Pyrazinamide (PZA) is an unconventional front line tuberculosis drug characterized by high in vivo sterilizing activity, but poor in vitro activity. This disparity in PZA activity may reflect differences between the in vivo tissue environment and in vitro culture conditions. This study examined the effect of anaerobic conditions, which exist in granulomatous lesions in vivo, on PZA activity in vitro. Low oxygen enhanced the activity of PZA against Mycobacterium tuberculosis, with anaerobic conditions resulting in greater enhancement than microaerobic conditions. ATPase and respiratory chain enzyme inhibitors enhanced PZA activity under normal atmospheric conditions, but not under anaerobic conditions. Furthermore, the inhibitors did not enhance isoniazid or rifampicin activity. Nitrate as an alternative electron acceptor antagonized PZA activity under anaerobic conditions. These findings provide further support for a proposed mechanism of action of PZA in which the active form of PZA (pyrazinoic acid) depletes the membrane energy reserve. They also provide another explanation for the higher sterilizing activity of PZA within in vivo lesions with low oxygen than under in vitro drug susceptibility testing conditions with ambient oxygen.

Topics: Adenosine Triphosphatases; Anaerobiosis; Antitubercular Agents; Colony Count, Microbial; Electron Transport; Energy Metabolism; Enzyme Inhibitors; Isoniazid; Mycobacterium tuberculosis; Nitrates; Oxygen; Pyrazinamide; Rifampin

A study was undertaken with the aim of assessing the killing capacity of rifampicin, pyrazinamide, and pyrazinoic acid on macrophage-ingested, live Mycobacterium tuberculosis. The 3 drugs were used at concentrations corresponding to the average peak levels observed in humans after administration of therapeutic doses that had been found to penetrate into macrophages in a previous study. The degree of killing was studied after exposure of the cell cultures to the individual drugs and their combinations for 3, 18, 24, 48, and 72 h. Comparing the degree of killing in the control, drug-free cultures with that observed in the drug-containing systems, over a period of 3 to 24 h, indicated that in these a greater, more rapid, although not statistically significant, killing of intracellular mycobacteria took place. At 48 h the degree of killing was similar in the control and in the drug-containing cell cultures. Between 48 and 72 h, however, a marked growth of intracellular mycobacteria was observed in the control cultures. This phenomenon was much less evident in the drug-containing cultures. No major increase in the killing effect with respect to that observed with the individual drugs was found after exposure of the macrophages to all possible combinations of the 3 drugs.

Topics: Animals; Antitubercular Agents; Drug Combinations; Macrophages; Male; Mice; Mice, Inbred BALB C; Mycobacterium tuberculosis; Phagocytosis; Pyrazinamide; Rifampin

The absorption and metabolism of streptomycin, isoniazid, rifampicin, and pyrazinamide were evaluated after administration of each drug alone and in combination. In the combination sessions, isoniazid, rifampicin, and pyrazinamide were administered orally, either individually or in a single fixed-ratio triple preparation. The results have shown that the pattern of absorption and metabolism (acetyl-isoniazid, desacetyl-rifampicin, and pyrazinoic acid) found after administration of each drug alone did not differ from that found after administration of the drugs in free and fixed combination. The 3 orally administered drugs given in a fixed combination resulted in a reduction of the order of 50% of the total number of tablets to be ingested.

Topics: Absorption; Antitubercular Agents; Humans; Isoniazid; Kinetics; Male; Pyrazinamide; Rifampin; Streptomycin

The degree of penetration of rifampicin, pyrazinamide, and its metabolite pyrazinoic acid in mouse macrophages was evaluated over a period of 24 h. Cell cultures were exposed to 14C-labeled drugs at concentrations corresponding to peak, trough, and intermediate serum concentrations observed in humans after administration of therapeutic doses. The study was carried out with dead, resident, and stimulated peritoneal macrophages. The results indicated that the 3 compounds penetrate macrophages rapidly. At the lower concentrations, uptake of the 3 drugs is practically complete. With increasing concentrations, the absolute amount in the intracellular compartment increased. Comparison of the degree of penetration of the 3 drugs into dead, resident, and stimulated macrophages seems to suggest that the process of transfer through the macrophage wall is of a passive nature and not related to the metabolic state of the cells. Analysis of the binding of the 3 drugs to intracellular proteins indicated that more binding sites are probably available for rifampicin than for the other 2 drugs.

Topics: Animals; Binding Sites; Biological Transport; Cells, Cultured; Dose-Response Relationship, Drug; Macrophages; Male; Mice; Mice, Inbred BALB C; Pyrazinamide; Rifampin

Topics: Drug Therapy, Combination; Humans; Joint Diseases; Pain; Pyrazinamide; Rifampin; Tuberculosis, Pulmonary; Uric Acid