RESUMEN
The aim of this study was to determine the level of clenbuterol residues in muscle tissue of pigs after repeat administration in a growth-promoting dose. An anabolic dose of clenbuterol (20 µg/kg body mass per day) was administered orally to experimental group (n=12) for 28 days, whereas control animals (n=3) were left untreated. Clenbuterol treated pigs were randomly sacrificed (n=3) on days 0, 3, 7 and 14 of treatment discontinuation and clenbuterol residues determined in muscle tissue. Determination of residual clenbuterol was by enzyme-linked immunosorbent assay (ELISA) as a screening method and liquid chromatography tandem mass spectrometry (LC-MS/MS) as a confirmation method. The highest clenbuterol content in the muscle of treated animals was recorded on day 0 of treatment cessation (4.40±0.37 ng/g) and significantly (p<0.05) exceeded the maximum residue limit (MRL) of 0.1 ng/g. On day 3 of withdrawal, it was 0.49±0.22 ng/g and on day 7 0.10±0.02 ng/g (at MRL); on day 14 of treatment discontinuation, clenbuterol content was below the limit of detection (<0.1 ng/g) in all samples. Administration of clenbuterol as a growth promoter in pig production could lead to residues in meat for human consumption up to 7 days after treatment discontinuation.