Detection of urine and blood clenbuterol following short-term oral administration in the horse

Material and methods: Urine and blood samples were collected following 3-day multiple oral administrations. The samples were examined using enzyme-linked immunosorbent assay and further confirmed by solid phase extraction and capillary electrophoresis. Results: Urinary clenbuterol was detectable until day 14 after the last dose. The urinary excretion of clenbuterol was characterized by a biphasic pattern. The half-lives of the bi-exponential elimination (t(1/2 alpha) and t(1/2 beta)) for urinary clenbuterol were about 12.1 and 48 hours. After a single oral administration (4 mu g/kg) of clenbuterol, the half-life of serum clenbuterol was approximately 11.4 hours.