Enhanced activity of rifampicin loaded with polybutyl cyanoacrylate nanoparticles in relation to intracellularly localized bacteria]

Association of rifampicin with polybutylcyanoacrylate nanoparticles provided considerable enhancement of drug antibacterial activity. In vitro nanoparticle-loaded rifampicin was more active against Staphylococcus aureus and Mycobacterium avium, localized in isolated alveolar macrophages. Level of rifampicin in macrophages increased 2-3-fold after incubation with rifampicinloaded nanoparticles comparing to the free drug. High therapeutic efficacy of colloidal rifampicin was demonstrated in vivo. Use of nanoparticles provided 2-fold increase in rifampicin efficacy, comparing with the free drug at treatment of staphylococcus sepsis in mice. Single administration of nanoparticulate rifampicin in the dose 25 mg/kg resulted in 80% survival of mice with salmonellosis, while 50 mg/kg of free rifampicin could provide only 10% survival. It may be considered that high antibacterial efficacy of rifampicin bound to nanoparticles is due to its effective delivery to macrophages.     

Development and estimation of nanosomal rifampicin]

A lab-scale method for preparation of rifampicin-loaded polybutylcyanoacrylate nanoparticles (nanosames) was developed. The biodistribution of the nanosome-entrapped rifampicin after its intravenous administration was studied on healthy mice. The nanoparticles provided significant liver and spleen accumulation of rifampicin. Modification of the nanoparticles surface with poloxamer 407 or poloxamine 908 led to optimization of the biodistribution: the concentrations of rifampicin in the lungs and plasma increased, whereas the liver accumulation decreased vs. the unmodified nanoparticles. The increased lung accumulation of rifampicin enhanced bacterial clearance in the lungs of the mice infected with M. tuberculosis. The results showed that the use of the nanoparticles for optimization of the drug biodistribution was effective for increasing the efficacy of antiinfective chemotherapy.     

The rifampicin drug delivery system based on phospholipid nanoparticles

Low bioavailability of rifampicin, one of the main antituberculous agents, stimulates searches of its new optimized formulations. The present study has shown a possibility of rifampicin incorporation into nanoparticles from plant phosphatidylcholine (diameter of 20–30 nm). Addition of sodium oleate to the phospholipid system caused a 2-fold increase in the percent of rifampicin incorporation. The maximal concentration of rifampicin assayed in plasma samples by LC/MS was observed 1 h after oral administration to rats (6 mg/kg) and represented 0.5 and 4.2 μg/mL for free rifampicin and rifampicin incorporated in the phospholipids-oleate nanoparticles, respectively. These levels were maintained for more than 2 h of the experiment. High rifampicin bioavailability in the oleate containing phospholipid nanosystem suggests its prospects for practical use.     

Biotransformation of rifampicin in pulmonary tuberculosis patients

Biotransformation of rifampicin in 39 tuberculosis patients treated with the drug was studied. The studies showed that biotransformation of rifampicin was most intensive during the first 3--6 hours after its use, which was confirmed by excretion of maximum amounts of rifampicin and its metabolites with the urine. 2--4 weeks after the beginning of the treatment with rifampicin excretion of its metabolism products decreased. When rifampicin was used simultaneously in a single dose with tubazid excretion of rifampicin transformation product and desacetylation of the antibiotic slowed down.     

Tissue Distribution of Berberine and Its Metabolites after Oral Administration in Rats

Berberine (BBR) has been confirmed to have multiple bioactivities in clinic, such as cholesterol-lowering, anti-diabetes, cardiovascular protection and anti- inflammation. However, BBR’s plasma level is very low; it cannot explain its pharmacological effects in patients. We consider that the in vivo distribution of BBR as well as of its bioactive metabolites might provide part of the explanation for this question. In this study, liquid chromatography coupled to ion trap time-of-flight mass spectrometry (LC/MSⁿ-IT-TOF) as well as liquid chromatography that coupled with tandem mass spectrometry (LC-MS/MS) was used for the study of tissue distribution and pharmacokinetics of BBR in rats after oral administration (200 mg/kg). The results indicated that BBR was quickly distributed in the liver, kidneys, muscle, lungs, brain, heart, pancreas and fat in a descending order of its amount. The pharmacokinetic profile indicated that BBR’s level in most of studied tissues was higher (or much higher) than that in plasma 4 h after administration. BBR remained relatively stable in the tissues like liver, heart, brain, muscle, pancreas etc. Organ distribution of BBR’s metabolites was also investigated paralleled with that of BBR. Thalifendine (M1), berberrubine (M2) and jatrorrhizine (M4), which the metabolites with moderate bioactivity, were easily detected in organs like the liver and kidney. For instance, M1, M2 and M4 were the major metabolites in the liver, among which the percentage of M2 was up to 65.1%; the level of AUC _(0-t) (area under the concentration-time curve) for BBR or the metabolites in the liver was 10-fold or 30-fold higher than that in plasma, respectively. In summary, the organ concentration of BBR (as well as its bioactive metabolites) was higher than its concentration in the blood after oral administration. It might explain BBR’s pharmacological effects on human diseases in clinic.     

The role of propylene glycol metabolism in lactatemia in the rabbit.

Propylene glycol (1,2-propanediol PD) has been reported to significantly alter the blood parameters when administered as a drug vehicle. In this study, experiments were performed to estimate the pH, levels of PD, and its metabolites to determine the acute effect of PD in blood. PD was administered to rabbits orally in a single dose of 1 ml 28.4% aqueous solution per 100 g body weight equivalent to 38.66 mmol/kg. Whole blood pH and the levels of PD and metabolites were estimated at fast (O.O h, before feeding PD) and at 0.25, 1, and 3 h after the dose. PD elevated the concentrations of blood PD to its maximum (41.04 +/- 9.98 mmol/liter, n = 4) at 1 h; whereas blood PD is normally absent during fasting. PD significantly increased (P less than 0.01) the concentration of L-lactate in blood, which reached its plateau (2.55 +/- 0.62 mmol/liter, n = 4) at 0.25 h and was 2.45-fold higher than the observed fasted values (1.04 +/- 0.22 mmol/liter, n = 4). Production of D-lactate in blood was similarly increased significantly from 5.1 +/- 5.0 mumols/liter at fast to 150.0 +/- 30.4 mumols/liter at 3 h after oral PD (P less than 0.001, n = 4). As was observed in the fasted blood of PD treated rabbits, D-lactate levels at fast and after saline ingestion in the control animals was found either absent or too low. Despite this increase in lactate, blood pH did not alter significantly when appropriate anticoagulant, i.e., heparin + 4-methylpyrazole, was employed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective action of rifampicin in experimental rabies infection of albino mice

The paper presents the results of the experimental study of the action of rifampicin on the process of rabies infection in albino mice contaminated with 1-10 LD50 of the fixed rabies virus. Exposure to rifampicin in doses of 250 and 500 micrograms/mouse (35-70 mg/kg) resulted in survival of 66.7 and 83.4 per cent of the animals respectively while in the controls it did not exceed 16.6 and 25.0 per cent. The average life-span of the albino mice treated with the antibiotic increased 1.6-2.4-fold in comparison with the controls. The chemotherapeutic index of rifampicin representing the ratio of the maximum tolerance dose to the minimum dose providing the protective action was equal to 20. The protective action was observed either after administration of the antibiotic according to the treatment-and-prophylaxis scheme or after administration of its 2- or 3-fold dose once a day immediately after the contamination.     

Rifampicin reduces effectiveness and bioavailability of prednisolone.

Rifampicin is an inducer of hepatic drug metabolising enzymes. This results in interactions with several drugs including oral anticoagulants, hypoglycaemics, and contraceptives. Concurrent treatment with prednisolone and rifampicin is given when tuberculosis coexists with a disease that is sensitive to steroids, when the diagnosis is uncertain, or occasionally in the treatment of severe tuberculosis. Two patients with respiratory disease were treated with both drugs: their condition improved considerably after rifampicin was withdrawn. Seven patients were then studied to assess the effect of rifampicin on the pharmacokinetics of prednisolone. Overall, rifampicin increased the plasma clearance of prednisolone by 45% and reduced the amount of drug available to the tissues (area under the plasma concentration time curve) by 66%. The effectiveness of prednisolone may be considerably reduced when rifampicin and prednisolone are used in combination.     

Rifampicin Inhibition of Ribonucleic Acid and Protein Synthesis in Normal and Ethylenediaminetetraacetic Acid-Treated Escherichia coli

The kinetics of ribonucleic acid (RNA) and protein synthesis in rifampicin-inhibited normal and ethylenediaminetetraacetic acid (EDTA)-treated Escherichia coli was measured. Approximately 200-fold higher external concentrations of rifampicin were needed to produce a level of inhibition in normal cells comparable to that observed in EDTA-treated cells. The rates of RNA and protein synthesis in both kinds of cells decreased exponentially, after an initial lag phase, at all rifampicin concentrations tested. The lag phase was longer and the final exponential slope less for protein synthesis than for RNA synthesis at a given rifampicin concentration. Below certain rifampicin concentrations, both the lag phase and the subsequent exponential decrease in the rates of RNA and protein synthesis were found to be rifampicin concentration dependent. At greater concentrations only the time of the lag phase was decreased by higher rifampicin concentrations, whereas the slope of the exponential decrease in the rates of RNA and protein synthesis was unaffected. In all cases, the exponential decrease continued to at least a 99.8% inhibition of the original rate of synthesis. These in vivo results are consistent with the mode of rifampicin action determined from in vitro studies; rifampicin prevents initiations of RNA polymerase on deoxyribonucleic acid, but not its propagation, by binding the enzyme essentially irreversibly. The results also indicate the size distribution of messenger RNA molecules in E. coli under our conditions.     

Distribution of the 14C-hydrated analog of phenazepam in the organs and tissues of mice

The absorption kinetics of hydrated phenazepam analog into the liver, spleen, brain, kidney, blood, lungs, heart, skeletal and fat tissues is studied at 0.25-24 hour intervals after its intraperitoneal (i/p) administration to mice. Drug concentration in the above mentioned organs was maximal 0.5-1 hour later. The decrease of the drug and its metabolite level in the organs under study is a biexponential process, consisting of "quick" (1-6 hours) and "slow" phases. The rate of absorption of hydrated phenazepam analog into the organs and tissues and its elimination is lower than that of phenanzepam.     

Schedule dependent variation in human lymphocyte sensitivity to bleomycin and repair of chromosomal aberrations in G2.

Bleomycin (BLM) induced chromosomal damage in G2 phase and its repair kinetics in normal human lymphocytes were studied following different treatment schedules. As a first step, a dose-response curve was obtained (concentrations of 5-50 micrograms/ml). For repair kinetics studies, blood samples were treated with BLM at a concentration of 20 micrograms/ml. Continuous treatment produced equal numbers of breaks per cell (br/c) when the cells were treated 3, 4 or 5 h before fixation. If the treatment time was extended to 6 h, the level of br/c was increased 2-fold (p < 0.001) as a result of an increased number of cells with more than 3 br/c. The curves obtained after pulse treatment showed maximal chromosome damage at time 3 (45 min BLM treatment, followed by 2 h repair in drug free medium). When the time after treatment was extended to 4 h (treatment time 5), a 50% reduction in chromosome damage was measured. It was found out that at treatment points 3, 4 and 5 the differences in breaks per cell at the different schedules applied were statistically highly significant. If caffeine (CAF) was added, the continuous treatment, BLM+CAF, induced a statistically significant increase in the frequency of br/c at every treatment point, but the shape of the curve illustrating the kinetics of chromosomal damage remained unchanged. Moreover, the addition of CAF at continuous BLM treatment brings the level of br/c close to that measured at the pulse BLM treatment except for treatment time 3. When applied in a combination with BLM, CAF considerably modified the kinetics of chromosome damage for a pulse (BLM alone) treatment. The possible reasons for the changes in the level of br/c as well as a tentative scheme for assessment of chromosome damage repair capacity after BLM treatment are discussed.     

Evaluation of the sanative action of rifampicin on the meningococcal carrier state]

The results of the epidemiological control experiment on the efficacy of rifampicin in sanation of meningococci carriers are presented. The preliminary study of rifampicin sensitivity of 41 freshly isolated nasopharyngeal meningococcal strains showed that the MIC of the drug for 63 per cent of the isolates was 0.04--0.1 gamma/ml. Sanation was performed for 2 days; 1.2 g of the drug was used during the treatment course. The results of examination of 91 meningococci carriers showed that 4 days after the sanation the specific weight of the persons isolating no meningococci was reliably higher in the experimental group than that in the control group. The coefficient of rifampicin efficiency was 70.8 per cent. 10 days after sanation the difference in the level of the carriers isolating no meningococci in the experimental and the control groups was statistically insignificant. Therefore, the carriers treated with the drug received temporary protection from the causative agent at an average for 1 week. Later on they could become carriers again. As a result of sanation no changes in the meningococcal sensitivity to rifampicin was observed.     

Pharmacokinetic study of rifampicin in the body of pregnant animals]

The study on distribution of 14C-rifampicin administered intramuscularly to pregnent animals showed that its concentrations in the blood, liver, kidneys, lungs and other organs did not practically change from those in nonpregnant animals. The concentration of 14C-rifampicin in the fetus organs was much lower than that in the organs of the adult animals. The liver and kidneys of the pregnant animals, as well as the fetus though to a less extent had a capacity for metabolism of 14C-rifampicin. The following products of biotransformation were detected: N-oxide of rifampicin, 25-deacetylrifampicin, 3-formylrifamycin SV and rifamycin SV.     

Improved Bioavailability of a Water-Insoluble Drug by Inhalation of Drug-Containing Maltosyl-β-Cyclodextrin Microspheres Using a Four-Fluid Nozzle Spray Drier

We previously developed a unique four-fluid nozzle spray drier that can produce water-soluble microspheres containing water-insoluble drug nanoparticles in one step without any common solvent between the water-insoluble drug and water-soluble carrier. In the present study, we focused on maltosyl-β-cyclodextrin (malt-β-CD) as a new water-soluble carrier and it was investigated whether drug/malt-β-CD microspheres could improve the bioavailability compared with our previously reported drug/mannitol (MAN) microspheres. The physicochemical properties of bare drug microparticles (ONO-2921, a model water-insoluble drug), drug/MAN microspheres, and drug/malt-β-CD microspheres were evaluated. In vitro aerosol performance, in vitro dissolution rate, and the blood concentration profiles after intratracheal administration were compared between these formulations. The mean diameter of both drug/MAN and drug/malt-β-CD microspheres was approximately 3–5 μm and both exhibited high aerosol performance (>20% in stages 2–7), but drug/malt-β-CD microspheres had superior release properties. Drug/malt-β-CD microspheres dissolved in an aqueous phase within 2 min, while drug/MAN microspheres failed to dissolve in 30 min. Inhalation of drug/malt-β-CD microspheres enhanced the area under the curve of the blood concentration curve by 15.9-fold than that of bare drug microparticles and by 6.1-fold than that of drug/MAN microspheres. Absolute bioavailability (pulmonary/intravenous route) of drug/malt-β-CD microspheres was also much higher (42%) than that of drug/MAN microspheres (6.9%). These results indicate that drug/malt-β-CD microspheres prepared by our four-fluid nozzle spray drier can improve drug solubility and pulmonary delivery.

Electronic supplementary material

The online version of this article (doi:10.1208/s12249-012-9826-z) contains supplementary material, which is available to authorized users.KEY WORDS: 4-fluid nozzle spray drier, inhalation therapy, maltosyl-β-cyclodextrin, microparticles, water-insoluble drug     

Use of rifamethoprim in acute and chronic respiratory tract diseases]

Rifamethoprim is a new formulation containing rifampicin and trimethoprim. Its efficacy was studied in the treatment of a group of patients with various nonspecific diseases of the lungs. It was shown to be highly active against a broad spectrum of pathogens. With inclusion of trimethoprim to the formulation it appeared possible to markedly lower the bacterial ability to develop resistance to rifampicin, which solved the problem of long-term antibiotic use. The unique pharmacokinetic properties of rifampicin such as its capacity to penetrating into the sputum, lung tissues and cells make rifamethoprim be the drug of optimal choice in the treatment of respiratory diseases.     

A rapid and sensitive HPLC-MS method for the detection of plasma and cellular rifampicin

Rifampicin is active against both intracellular and extracellular Mycobacterium tuberculosis. The ability to measure rifampicin drug concentrations in both plasma and in cells may be useful in evaluating the suitability of dosage regimens for populations and individuals. Here a novel simple, precise and accurate method for the quantification of rifampicin in both cells and plasma is reported. Sample proteins were precipitated with acetonitrile containing the internal standard and then diluted with water. Aliquots of supernatant were then injected into the HPLC-MS system for chromatographic separation and detection. Rifampicin calibration curves encompassed concentrations from 100 to 12,800 ng/mL. Intra- and inter-assay precision and accuracy were determined using low, medium and high concentration quality control samples and was found to be within 10% in all cases. Rifampicin concentrations were found to be unaffected by freeze-thaw cycles, but were significantly affected by heat-inactivation (58 degrees C, 40 min). This assay was successfully utilised to determine the pharmacokinetic profile of rifampicin in plasma and peripheral blood mononuclear cells (PBMC) in 8 tuberculosis patients receiving rifampicin over an 8h period.     

Pulmonary microvascular response to LTB4: effects of perfusate composition

We examined the effects of leukotriene B4 (LTB4) on pulmonary hemodynamics and vascular permeability using isolated perfused guinea pig lungs and cultured monolayers of pulmonary arterial endothelial cells. In lungs perfused with Ringer solution, containing 0.5 g/100 ml albumin (R-alb), LTB4 (4 micrograms) transiently increased pulmonary arterial pressure (Ppa) and capillary pressure (Pcap). Pulmonary edema developed within 70 min after LTB4 injection despite a normal Pcap. The LTB4 metabolite, 20-COOH-LTB4 (4 micrograms), did not induce hemodynamic and lung weight changes. In lungs perfused with autologous blood hematocrit = 12 +/- 1%; protein concentration = 1.5 +/- 0.2 g/100 ml), the increases in Ppa and Pcap were greater, and both pressures remained elevated. The lung weight did not increase in blood-perfused lungs. In lungs perfused with R-alb (1.5 g/100 ml albumin) to match the blood perfusate protein concentration, LTB4 induced similar hemodynamic changes as R-alb (0.5 g/100 ml) perfusate, but the additional albumin prevented the pulmonary edema. LTB4 (10(-11)-10(-6) M) with or without the addition of neutrophils to the monolayer did not increase endothelial 125I-albumin permeability. Therefore LTB4 induces pulmonary edema when the perfusate contains a low albumin concentration, but increasing the albumin concentration or adding blood cells prevents the edema. The edema is not due to increased endothelial permeability to protein and is independent of hemodynamic alterations. Protection at higher protein-concentration may be the result of LTB4 binding to albumin.     

Pharmacokinetics and biotransformation of rifamycins in the body of experimental animals]

The study on distribution of 14C-rifampicin and 14C-rifamycin S in experimental animals after intramuscular administration of the drugs showed that concentrations of rifampicin in the organs and blood were higher than those of rifamycin S. Biotransformation products of both antibiotics, such as 25-deacetylrifampicin, N-oxide of rifampicin, 3-phormylrifamycin SV, rifamycin SV and others were found in the liver, kidneys, bile and urine. No products of the antibiotic metabolism were found in the blood, lungs and spleen.     

The patterns of extracellular protein formation by spontaneously-occurring rifampicin-resistant mutants of Staphylococcus aureus

Spontaneously-occurring rifampicin-resistant mutants of Staphylococcus aureus were isolated on 4% (w/v) Tryptone Soya Agar containing 4 and 40 times the m.i.c. for rifampicin. A number of colonies were selected at each rifampicin concentration and were grown aerobically in 3% (w/v) Tryptone Soya Broth for 24 h at 37 degrees C. In the case of S. aureus RN4220 all the mutants grew to bacterial densities up to approximately 1.7 times more than the parent organism. The corresponding levels of extracellular protein secretion varied over a 5-fold range, all the mutants being less productive than the parent. By contrast, mutants of the wild-type Wood 46 strain achieved bacterial densities of only 45-83% that of the parent whilst exoprotein secretion showed a smaller 1.7-fold variation. However, widely-differing patterns of exoproteins were revealed by SDS-polyacrylamide gel electrophoresis of the parent and mutant organisms of both strains.     

Sensitivity to Rifampicin: Incidence,Mechanism, and Prevention

Five out of 200 patients taking rifampicin 900 mg twice weekly and three out of 91 patients taking rifampicin who attended an immunology clinic developed intolerance to the drug. Antibodies to rifampicin, which were found in most cases, decreased steadily after the end of treatment but were detectable for up to 16 months. The dose of rifampicin and the blood levels are predominating factors in the occurrence of reactions. Thus the dose should be reduced in patients in whom rifampicin blood levels rise abnormally. When it is important to continue rifampicin treatment despite intolerance antibody titres within 24 hours after administration of the drug must be measured to find when they are lowest, which determines the “unreactive period,” and when a further dose may be safely given.