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.