Distribution and elimination of clenbuterol in tissues and fluids of calves following prolonged oral administration at a growth‐promoting dose

Abstract

A pharmacokinetic study is described in which Friesian calves (n = 30) were treated orally with clenbuterol at 10 times the therapeutic dose. The study was designed to establish the distribution and elimination of clenbuterol from edible tissues, the major compartments of the eye and body fluids. Animals (n = 24) were dosed (10 micrograms/kg body weight) twice daily with clenbuterol for 21 days and slaughtered in groups of five (one untreated control animal per group) at 6 h and 1, 2, 4, 8 and 16 days after cessation of treatment. At slaughter, samples of diaphragm muscle, liver, kidney, bile, urine and both eyes were obtained. One of the eyes was separated into constituent tissues: aqueous humour, vitreous humour, cornea, lens, retina (without pigmented epithelium), choroid (with pigmented retinal epithelium; choroid/PRE) and sclera. All samples were stored at -20 degrees C. Clenbuterol concentrations were higher in liver than kidney, bile and urine from day 2 of withdrawal onwards. Concentrations in choroid/PRE were at least 10 times higher than in liver at all periods following cessation of treatment and 52 times higher 16 days after treatment. The concentrations of clenbuterol in the constituent tissues of the eye were in the order choroid/PRE > cornea > > retina > aqueous humour/vitreous humour > or = lens. Concentrations of clenbuterol in choroid/PRE taken from eyes frozen whole were generally lower than those in choroid/PRE separated before storage. Choroid/PRE stored by either method contained clenbuterol at more than 100 ng/g 16 days following cessation of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of MISPE for the multi-residue extraction of β-agonists from calves urine

“…Agonists were chosen as representative of the most abused growth promoters. The MPRL is consistent with the pharmacokinetics of ␤-agonists, such as clenbuterol [17] and ractopamine [18] in urine of farmed cattle, according to the proposed doses in feeds.…”

Liquid chromatography/electrospray tandem mass spectrometric analysis of incurred ractopamine residues in livestock tissues

“…Delayed elimination of ractopamine from retina is consistent with data from previous studies with clenbuterol 4,. 8,, 9 Another advantage of using retinal tissue was that this matrix contributed less interference than liver for the three MRM transitions (Figs 2 and 3), resulting in an improved limit of confirmation (see below). The same procedures described above were used to quantify ractopamine residues in retina (Table 2).…”

Analysis of clenbuterol residues in pig liver using liquid chromatography electrospray ionization tandem mass spectrometry

“…The results obtained in the present study are consistent with clenbuterol concentrations recorded in calf liver, which was found to decrease from 46 ng/g on day 0 to 0.5 ng/g on day 14 of treatment cessation (Meyer and Rinke 1991 ). This study found the liver to be more suitable as a matrix for clenbuterol detection than urine and plasma as control matrices (Pleadin et al 2009 ), thus liver tissue being considered appropriate for clenbuterol abuse monitoring (Sauer et al 1995 ). The sensitivity and specifi city of the chosen sample preparation and LC-ESI/MS/MS analysis conditions allow for the unambiguous identifi cation and quantifi cation of the target analyte in all liver samples collected from experimental animals.…”