Salbutamol Residues in Plasma, Urine and Hair of Heifers After a Single Dose and Throughout.

The objective of this study was to evaluate the salbutamol residues in the plasma, urine and hair of heifers after a single dose. Three heifers were given a single oral dose of salbutamol hydrochloride (150 μg/kg bodyweight). The salbutamol concentrations were measured in the plasma, urine (before and after hydrolysis with β-glucuronidase/arylsulfatase) and hair samples with ultra-performance liquid chromatography-tandem mass spectrometry. In the unhydrolyzed samples, the peak concentrations of salbutamol occurred in the plasma and urine at 12 and 8 h after drug administration, respectively, but were below the limit of quantification (LOQ = 0.2 ng/mL) at 48 and 120 h after administration, respectively. However, in the hydrolyzed samples, the salbutamol concentration was 1.1 ng/mL in the plasma 72 h after its administration and 0.7 ng/mL in the urine 168 h after its administration. Thus, the concentrations of salbutamol were significantly higher in the hydrolyzed samples than that in the unhydrolyzed samples (P < 0.01). The concentrations of salbutamol in the black and white hair 24 h after its administration were 1.7 and 1.0 ng/g, respectively. These results indicate that hair may be a target tissue for detecting the misuse of salbutamol after a single dose and that the primary forms of salbutamol in the plasma and urine samples from heifers are its sulfate and glucuronide conjugates.