Residue depletion of valnemulin in swine tissues after oral administration.

The depletion profile of valnemulin (VLM) was studied in healthy piglets after oral administration of a premix. Thirty pigs were given doses of 7.5 mg/kg body weight/day in the feed for 21 days. One control and five medicated piglets were randomly selected for sacrifice at 0.25, 0.5, 1, 2 and 3 days post-treatment. The residue concentrations of VLM in swine muscle, liver and kidney were detected using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The highest residue concentrations of VLM were attained in 0.25 day, and all of the samples were below the maximum residue limit (MRL) recommended by the European Medical Evaluation Agency (EMEA) at 0.5 day post-treatment. The residue concentrations of swine liver were significantly higher than those of kidney and muscle, which indicated liver to be the target tissue for VLM. The withdrawal period of VLM with oral administration was 24 hours.