Furazolidone residues in chicken and swine tissues after feeding trials

Depletion of four nitrofuran antibiotics and their tissue-bound metabolites in porcine tissues and determination using LC-MS/MS and HPLC-UV

Depletion of the nitrofuran antibiotics furazolidone, furaltadone, nitrofurantoin and nitrofurazone and their tissue-bound metabolites AOZ, AMOZ, AHD and SEM from pig muscle, liver and kidney tissues is described. Groups of pigs were given feed medicated with one of the nitrofuran drugs at a therapeutic concentration (400?mg?kg(-1)) for ten days. Animals were slaughtered at intervals and tissue samples collected for analysis for six weeks following withdrawal of medicated feed. These samples were analysed both for parent nitrofurans (using LC-MS/MS and HPLC-UV), and for tissue-bound metabolites (using LC-MS/MS). The parent drugs were detectable only sporadically and only in pigs subjected to no withdrawal period whatsoever. This confirms the instability of the four major nitrofuran antibiotics in edible tissues. In contrast, the metabolites accumulated to high concentrations in tissues (ppm levels) and had depletion half lives of between 5.5 and 15.5 days. The metabolites of all four drugs were still readily detectable in tissues six weeks after cessation of treatment. This emphasizes the benefits of monitoring for the stable metabolites of the nitrofurans.

Binding of 14C-furazolidone metabolites to the muscular and hepatic proteins of trout

A high level of 14C was found to bind irreversibly with the liver proteins of rainbow trout (Oncorhyncus mykiss) exposed to 135 mg/kg bodyweight of 14C-labelled furazolidone (14C-FZ) in fish feed daily for 10 days. After the cessation of 14C-FZ treatment, hepatic protein-bound 14C in trout stayed high for at least 30 days. The chemical identity of protein-bound 14C remained to be elucidated. However, a part of the protein-bound 14C in the liver and muscle could be released as 3-amino-2-oxazolidinone by acid hydrolysis. The formation of protein-bound 14C in the liver was investigated further with trout dosed intravenously with different 14C-FZ doses at 10 degrees C or with 5 mg/kg FZ at different water temperatures. 14C binding to the liver proteins was found to increase with increasing FZ dose or water temperature. Results of these studies indicate that protein-bound 14C in the muscle and liver of trout is related to the formation of reactive intermediates from FZ. However, additional studies on the identities of the protein-bound FZ residues are required before they can serve as useful biomarkers to monitor FZ exposure in farm fish.

[The residue behavior of the furazolidone metabolite 3-(4-cyano-2-oxobutylideneamino)-2-oxazolidone in trout]

A high-performance liquid chromatography (HPLC)-method for the determination of furazolidone (FZ) and its open-chain cyano-derivative 3-(4-cyano-2-oxobutylideneamino)-2-oxazolidone (M1) in trout is described. Only during the medication period residues of FZ and M1 were detected in the muscle and liver of the trout, which were treated with food containing FZ over a period of 7 days. After the beginning of the withdrawal period, the concentration of FZ and M1 were found to be under the limits of detection.

The elimination of furazolidone and its open-chain cyano-derivative from adult swine

1. A sensitive method for the determination of 3-(4-cyano-2-oxobutylidene amino)-2-oxazolidone, the open-chain cyano-derivative of the veterinary drug furazolidone, in swine plasma and tissues is described. 2. After dosing adult swine orally with furazolidone (690 mg/animal per day) for 10 days no furazolidone was detected in liver, kidney and muscle (less than 2 ng/g). The half life of furazolidone as measured from the terminal phase of the plasma curves was 45 minutes. In urine, small amounts (less than 0.3% of total dose) of furazolidone were detected. 3. In contrast to other animals, 3-(4-cyano-2-oxobutylidene amino)-2-oxazolidone is a minor metabolite in swine with a plasma half life of 4 h. No cyano-derivative was detected in liver and kidney (less than 5 ng/g) 2 h after the last administration of furazolidone; 24 h after the last administration, the concentration in plasma was less than 2 ng/ml and in muscle less than 5/g. 4. The cyano-derivative was not mutagenic in the Salmonella/microsome test, with or without metabolic activation.

Determination of furazolidone residues in eggs by HPLC followed by confirmation with a diode-array UV/Vis detector

A sensitive HPLC method for the determination of furazolidone residues in eggs (10-1,000 micrograms/kg) is described. Recovery is about 86%. With the aid of a UV/Vis Diode-Array detector confirmation up to the 15-ppb level was possible. In order to test this method with "real" samples, three laying hens received 30 mg each of furazolidone in feed (single dose). The eggs were collected for five days. After five days traces of furazolidone (5 micrograms/kg) could still be detected.