Effects of anemoside B4 on pharmacokinetics of florfenicol and mRNA expression of CXR, MDR1, CYP3A37 and UGT1E in broilers.

Pulsatillae radix, a traditional Chinese medicine (TCM), is often used in combination with florfenicol for treatment of intestinal infection in Chinese veterinary clinics. Anemoside B4 (AB4) is the major effective saponin in Pulsatillae radix. This study aimed to investigate whether the pharmacokinetics of florfenicol in broilers was affected by the combination of AB4. In this study, broilers were given AB4 (50 mg/kg BW), or 0.9% sodium chloride solution by oral administration for 7 days. They were then fed florfenicol orally (30 mg/kg BW) on the eighth day. The results showed that the AUC(0-∞), MRT(0-∞), t1/2z and Cmax of florfenicol were significantly decreased, and the Vz/F and CLz/F were significantly increased by AB4; the mRNA expression levels of CXR, CYP3A37 and MDR1 (except CXR and CYP3A37 in the liver) were up-regulated by AB4. In conclusion, AB4 altered the pharmacokinetics of florfenicol, resulting in lower plasma concentrations of florfenicol, this was probably related to the mRNA expression of CXR, CYP3A37 and MDR1 in the jejunum and liver (except CXR and CYP3A37) increased by AB4. The implications of these findings on the effect of traditional Chinese medicine containing AB4 on the effectiveness of florfenicol in veterinary practice deserve study.

Comparison of Active Drug Concentrations in the Pulmonary Epithelial Lining Fluid and Interstitial Fluid of Calves Injected with Enrofloxacin, Florfenicol, Ceftiofur, or Tulathromycin.

Bacterial pneumonia is the most common reason for parenteral antimicrobial administration to beef cattle in the United States. Yet there is little information describing the antimicrobial concentrations at the site of action. The objective of this study was to compare the active drug concentrations in the pulmonary epithelial lining fluid and interstitial fluid of four antimicrobials commonly used in cattle. After injection, plasma, interstitial fluid, and pulmonary epithelial lining fluid concentrations and protein binding were measured to determine the plasma pharmacokinetics of each drug. A cross-over design with six calves per drug was used. Following sample collection and drug analysis, pharmacokinetic calculations were performed. For enrofloxacin and metabolite ciprofloxacin, the interstitial fluid concentration was 52% and 78% of the plasma concentration, while pulmonary fluid concentrations was 24% and 40% of the plasma concentration, respectively. The pulmonary concentrations (enrofloxacin + ciprofloxacin combined) exceeded the MIC90 of 0.06 µg/mL at 48 hours after administration. For florfenicol, the interstitial fluid concentration was almost 98% of the plasma concentration, and the pulmonary concentrations were over 200% of the plasma concentrations, exceeding the breakpoint (≤ 2 µg/mL), and the MIC90 for Mannheimia haemolytica (1.0 µg/mL) for the duration of the study. For ceftiofur, penetration to the interstitial fluid was only 5% of the plasma concentration. Pulmonary epithelial lining fluid concentration represented 40% of the plasma concentration. Airway concentrations exceeded the MIC breakpoint for susceptible respiratory pathogens (≤ 2 µg/mL) for a short time at 48 hours after administration. The plasma and interstitial fluid concentrations of tulathromcyin were lower than the concentrations in pulmonary fluid throughout the study. The bronchial concentrations were higher than the plasma or interstitial concentrations, with over 900% penetration to the airways. Despite high diffusion into the bronchi, the tulathromycin concentrations achieved were lower than the MIC of susceptible bacteria at most time points.

Intrabronchial Microdialysis: Effects of Probe Localization on Tissue Trauma and Drug Penetration into the Pulmonary Epithelial Lining Fluid.

Recent intrabronchial microdialysis data indicate that the respiratory epithelium is highly permeable to drugs. Of concern is whether intrabronchial microdialysis disrupts the integrity of the respiratory epithelium and thereby alters drug penetration into the pulmonary epithelial lining fluid (PELF). The objective of this study was to investigate the effect of intrabronchial microdialysis on the integrity of the bronchial epithelium. Microdialysis sampling in PELF in proximal (n = 4) and distal bronchi (n = 4) was performed after intravenous inulin and florfenicol administration in anaesthetized pigs. Inulin was used as a marker molecule of permeability of the epithelium, and florfenicol was used as test drug. Bronchial tissue was examined by histopathology (distal and proximal bronchi) and gene expression analysis (RT-qPCR, proximal bronchi) at the termination of the experiment (6.5 hr). The microdialysis probe caused overt tissue trauma in distal bronchi, whereas no histopathological lesions were observed in proximal bronchi. A moderate up-regulation of the pro-inflammatory cytokines IL1B, IL6 and acute-phase reactant serum amyloid A was seen in proximal bronchi surrounding the microdialysis probes suggesting initiation of an inflammatory response. The observed up-regulation is considered to have limited impact on drug penetration during short-term studies. Inulin penetrated the respiratory epithelium in both proximal and distal bronchi without any correlation to histopathological lesions. Likewise, florfenicol penetration into PELF was unaffected by bronchial histopathology. However, this independency of pathology on drug penetration may not be valid for other antibiotics. We conclude that short-term microdialysis drug quantification can be performed in proximal bronchi without disruption of tissue integrity.

Pharmacokinetics of florfenicol after intravenous administration in Escherichia coli lipopolysaccharide-induced endotoxaemic sheep.

Experiments in different animal species have shown that febrile conditions, induced by Escherichia coli lipopolysaccharide (LPS), may alter the pharmacokinetic properties of drugs. The objective was to study the effects of a LPS-induced acute-phase response (APR) model on plasma pharmacokinetics of florfenicol (FFC) after its intravenous administration in sheep. Six adult clinically healthy Suffolk Down sheep, 8 months old and 35.5 ± 2.2 kg in body weight (bw), were distributed through a crossover factorial 2 × 2 design, with 4 weeks of washout. Pairs of sheep similar in body weight were assigned to experimental groups: Group 1 (LPS) was treated with three intravenous doses of 1 µg/kg bw of E. coli LPS before FFC treatment. Group 2 (control) was treated with an equivalent volume of saline solution (SS) at similar intervals as LPS. At 24 h after the first injection of LPS or SS, an intravenous bolus of 20 mg/kg bw of FFC was administered. Blood samples (5 mL) were collected before drug administration and at different times between 0.05 and 48.0 h after treatment. FFC plasma concentrations were determined by liquid chromatography. A noncompartmental pharmacokinetic model was used for data analysis, and data were compared using a Mann-Whitney U-test. The mean values of AUC0-∞ in the endotoxaemic sheep (105.9 ± 14.3 µg·h/mL) were significantly higher (P < 0.05) than values observed in healthy sheep (78.4 ± 5.2 µg·h/mL). The total mean plasma clearance (CLT ) decreased from 257.7 ± 16.9 mL·h/kg in the control group to 198.2 ± 24.1 mL·h/kg in LPS-treated sheep. A significant increase (P < 0.05) in the terminal half-life was observed in the endotoxaemic sheep (16.9 ± 3.8 h) compared to the values observed in healthy sheep (10.4 ± 3.2 h). In conclusion, the APR induced by the intravenous administration of E. coli LPS in sheep produces higher plasma concentrations of FFC due to a decrease in the total body clearance of the drug.

Human nasal olfactory epithelium as a dynamic marker for CNS therapy development.

Discovery of new central nervous system (CNS) acting therapeutics has been slowed down by the lack of useful applicable biomarkers of disease or drug action often due to inaccessibility of relevant human CNS tissue and cell types. In recent years, non-neuronal cells, such as astrocytes, have been reported to play a highly significant role in neurodegenerative diseases, CNS trauma, as well as psychiatric disease and have become a target for small molecule and biologic therapies. We report the development of a method for measuring pharmacodynamic changes induced by potential CNS therapeutics using nasal olfactory neural tissue biopsy. We validated this approach using a potential astrocyte-targeted therapeutic, thiamphenicol, in a pre-clinical rodent study as well as a phase 1 human trial. In both settings, analysis of the olfactory epithelial tissue revealed biological activity of thiamphenicol at the drug target, the excitatory amino acid transporter 2 (EAAT2). Therefore, this biomarker approach may provide a reliable evaluation of CNS glial-directed therapies and hopefully improve throughput for nervous system drug discovery.

Serum and lung levels of thiamphenicol after administration of its glycinate N-acetylcysteinate ester in experimentally infected guinea pigs.

Thiamphenicol is an analogue of chloramphenicol and is characterised by a broad spectrum of action. In this study, serum and lung levels of thiamphenicol (TAP) were studied in infected guinea pigs after the administration of thiamphenicol glycinate N-acetylcysteinate (TGA). Animals received a single dose of TGA (15 mg/kg, subcutaneously) immediately after intra-tracheal infection with Haemophilus influenzae (about 10(7) CFU/animal). Serum and lung concentrations of TAP were determined at 0, 1, 3, 6, 12 and 24 h after drug administration by means of HPLC. TAP serum levels were elevated at 1 h and remained detectable for 24 h after drug administration. Tissue lung levels were comparable to peak serum concentrations but remained higher and decreased more slowly than serum concentrations.

[Observations on antibacterial activity of thiamphenicol glycinate acetylcysteinate (author's transl)]. / Osservazioni sull'attività antibatterica del tiamfenicolo glicinato acetilcisteinato.

In vitro thiamphenicol antibacterial activity in the presence of N-acetylcysteine as sodium salt proved to be enhanced when compared with that of the antibacterial alone against both Gram-positive and Gram-negative bacterial strains. The in vitro results were confirmed in vivo in the guinea-pig, where the sera from animals previously treated by i.m. route with thiamphenicol glycinate acetylcysteinate, showed a higher antibacterial activity than sera from animals treated with thiamphenicol glycinate hydrochloride. The observation, even after allowing for differences between species might be of some interest in view of use of this chemotherapeutic agent in the treatment of respiratory infections.

Concentration of thiamphenicol in the human prostate and testis.

The concentration of thiamphenicol in prostatic tissue, testicular tissue and serum after a single intravenous injection of 1 g thiamphenicol glycinate ester was investigated. The prostatic and testicular specimens were obtained by prostatectomy and plastic orchidectomy, respectively, from patients with adenomas and carcinomas of the prostate. 2 h after dosing, the prostatic tissue concentration ranged from 2.1 to 15.1 microgram/g (mean value 5.7 microgram/g) and the testicular tissue from 3.4 to 8.4 microgram/g (mean value 6.1 microgram/g). At the same time the thiamphenicol serum levels varied in the patients with prostate adenomas from 4.6 to 14.5 microgram/ml (mean 8.9 microgram/ml) and in the prostate carcinoma patients from 5.2 to 10.4 microgram/ml (mean 8.5 microgram/ml). Several factors influencing the diffusion of thiamphenicol into the prostate and testis are discussed. The levels of thiamphenicol in the prostate and testis suggest that the antibiotic may be valuable for the treatment of infections of the prostate and testis caused by gram-positive and gram-negative cocci, but is of questionable value for the treatment of infections caused by gram-negative bacilli.

The concentration of thiamphenicol in severely diseased human kidneys.

The concentration of thiamphenicol in serum and renal tissue was determined in 17 patients with severly diseased kidneys after an intravenous injection of 1000 mg of the drug. Two hours after the administration the renal tissue concentrations ranged in patients with hydronephrotic kidneys from 38.0-63.5 microgram/g, in patients with cirrhotic kidneys from 17.9-42.7 microgram/g, in patients with pyonephrosis from 9.8-17.6 microgram/g and in patients with renal carcinoma from 37.7-64.2 microgram/g. The patient with the renal sarcoma had a level of 138.7 microgram/g. At the same time the serum concentration ranged from 4.6-15.2 microgram/ml. The highest renal tissue/serum concentration ratios of thiamphenicol were observed in patients with hydronephrotic kidneys and renal tumours, the lowest in cases of pyonephrosis. The influence of severe renal disease on the renal tissue/serum concentration ratios of thiamphenicol is discussed. The high renal tissue levels of thiamphenicol in patients with severely diseased kidneys fulfill an important condition for the antibacterial chemotherapy of kidney infections.

A rapid gas chromatographic determination of thiamphenicol in plasma and amniotic fluid.

A rapid gas chromatographic method for the determination of thiamphenicol in plasma and amniotic fluid is described. The antibiotic is extracted from biological fluids with ethyl acetate and, after concentration of the extract, the trimethylsilyl derivative of the drug is determined by electron-capture gas chromatography using a 63Ni detector. After the intravenous administration of a single dose of 500 mg of thiamphenicol during the first stage of spontaneous labour to clinically normal gravidae at term, transmission of the drug across the placenta was demonstrated by a combination of gas chromatography and mass spectrometry.