Residue depletion of nifuroxazide in broiler chicken.

BACKGROUND: Several nitrofuran drugs have been prohibited for use in food producing animals due to their carcinogenic and mutagenic effects. However, one of the nitrofurans, nifuroxazide, is still used as a veterinary drug in some countries. This study was conducted to investigate the residue depletion of nifuroxazide in broiler chicken. Chickens were fed with dietary feeds containing 50 mg kg⁻¹ of nifuroxazide for seven consecutive days. Liver, kidney, muscle and plasma samples were collected at different withdrawal periods, and the residues of parent nifuroxazide and its acid-hydrolysable side chain, 4-hydroxybenzhydrazide (HBH), in these samples were determined. RESULTS: Nifuroxazide was metabolised in vivo and its metabolite HBH was formed. Parent nifuroxazide was not detectable in these samples after 14 days of cessation. HBH was detectable in these samples even after 28 days of cessation and the total HBH residues were higher than 1.0 ng g⁻¹. Furthermore, the residue level of tissue bound HBH was much higher than that of free HBH. CONCLUSION: The tissue-bound HBH could be used as a marker to monitor the residue of nifuroxazide in chicken and the best target tissue should be liver. This is the first paper reporting the residue depletion of nifuroxazide in chicken.

Detection of banned nitrofuran metabolites in animal plasma samples using UHPLC-MS/MS.

The use of nitrofurans as veterinary drugs in food-producing animals has been banned in the EU since the 1990s. Monitoring programs in the EU are based on the detection of protein-bound metabolites after slaughter. An UHPLC-MS/MS method was developed and validated for pre slaughter determination of four nitrofuran metabolites (AHD, AOZ, SEM, AMOZ) in animal plasma (bovine, ovine, equine and porcine). This method is proposed as an alternative method for on-farm surveillance. Plasma samples were derivatised with 2-nitrobenzaldehyde and subsequently extracted with organic solvent. Extracts were concentrated and then analysed by UHPLC-MS/MS. The method was validated according to Commission Decision 2002/657/EC. Inter-species recovery for AHD, AOZ, SEM and AMOZ was 72, 74, 57 and 71%, respectively. Decision limits (CCα) were calculated from within laboratory reproducibility experiments to be 0.070, 0.059, 0.071 and 0.054 µg kg(-1), respectively. In addition, the assay was applied to incurred plasma samples taken from pigs treated with furazolidone.

Pharmacokinetically-guided lead optimization of nitrofuranylamide anti-tuberculosis agents.

In an effort to develop novel and more potent therapies to treat tuberculosis, a new class of chemical agents, nitrofuranylamides, is being developed. The present study examines biopharmaceutic properties and preclinical pharmacokinetics of nitrofuranylamides at early stages of drug discovery to accelerate the optimization of leads into development candidates. The first tested compound, Lee 562, had high anti-tuberculosis activity in vitro, but exhibited poor metabolic stability resulting in a high systemic clearance, a short elimination half-life and low oral bioavailability in vivo in rats. Thus, two follow-up compounds were designed and tested that included structural modifications for increased metabolic stability. Both compounds showed improved metabolic stability compared to Lee 562, with Lee 878 being much more stable than Lee 952. As a consequence, the oral bioavailability of Lee 878 reached approximately 27% compared to 16% for the other two compounds. This observation prompted us to select compounds based on metabolic stability screening and a new set of nine compounds with high in vitro activity were tested for metabolic stability. The most stable compound in the assay, Lee 1106 was selected for further pharmacokinetic evaluation in rats. Surprisingly, Lee 1106 exhibited poor oral bioavailability, 4.6%. Biopharmaceutic evaluation of the compound showed that the compound has poor aqueous solubility and a high clogP. Based on these results, a screening paradigm was developed for optimization of the nitrofuranylamide lead compounds in a timely and cost-effective manner that might also be applicable to other classes of anti-infective drugs.

Determination of nifuroxazide in biological fluids by automated high-performance liquid chromatography with large-volume injection.

A high-performance liquid chromatographic method for the measurement of nifuroxazide in plasma is described. The technique is based on the single extraction of the drug from buffered plasma with chloroform, using nifuratel as internal standard. The chromatographic system consisted of a 15 cm x 4.6 mm I.D. stainless-steel column packed with Spherisorb ODS, 5 micrometer, and the mobile phase was acetonitrile-orthophosphoric acid (pH 2.5) (30:70). The method was able to measure accurately plasma nifuroxazide concentrations down to 2 ng . ml-1 using 2 ml of sample with no interference from endogenous compounds. The coefficients of variation of the method at 200 and 2 ng . ml-1 were 3% and 15%, respectively, and the calibration graph was linear in this range. The use of automatic injection makes the method suitable for the routine analysis of large numbers of samples.

Mutagenicity studies with nitrofurans. III. Mutagenicity testing of nitrofurylacrylic acid in human blood and urine.

Human blood and urine mutagenicity of 3-(5-nitro-2-furyl)acrylic acid (5-NFA) was analysed by using Salmonella typhimurium indicator strains TA100 AND TA98 and the cytogenetic analysis of human peripheral lymphocytes. 8 human volunteers were given doses of 1 g 5-NFA per os. The mutagenic effect in blood was analysed after 0, 0.5, 1, 2 and 4 h, in urine after 0, 2 and 4 h. Cytogenetic analysis was done 0, 24 and 72 h after administration of 5-NFA. The experiment was repeated with 3 volunteers in the course of 96 h. When each of 8 volunteers consumed 1 g of 5-NFA, the mutagenicity was observed in 6 blood samples 1 h after exposure for strain TA98 (doubled number or revertants) and in all urine samples taken between the 2nd and 6th hours for both strains used. 7 volunteers given 10 mg 5-NFA in wine (2 sets) showed no mutagenicity of blood or urine for TA100 or TA98 indicator strains. These results are believed to indicate an enhanced elimination of 5-NFA from the human body.