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Pharmacokinetics and disposition of clenbuterol in the horse
Author(s) -
Soma L. R.,
Uboh C. E.,
Guan F.,
Moate P.,
Luo Y.,
Teleis D.,
Li R.,
Birks E. K.,
Rudy J. A.,
Tsang D. S.
Publication year - 2004
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.2004.00553.x
Subject(s) - pharmacokinetics , urine , volume of distribution , horse , clenbuterol , plasma concentration , chemistry , half life , oral administration , pharmacology , medicine , chromatography , biology , paleontology
The pharmacokinetics of clenbuterol (CLB) following a single intravenous (i.v.) and oral (p.o.) administration twice daily for 7 days were investigated in thoroughbred horses. The plasma concentrations of CLB following i.v. administration declined mono‐exponentially with a median elimination half‐life ( t 1/2k ) of 9.2 h, area under the time–concentration curve ( AUC ) of 12.4 ng·h/mL, and a zero‐time concentration of 1.04 ng/mL. Volume of distribution ( V d ) was 1616.0 mL/kg and plasma clearance ( Cl ) was 120.0 mL/h/kg. The terminal portion of the plasma curve following multiple p.o. administrations also declined mono‐exponentially with a median elimination half‐life ( t 1/2k ) of 12.9 h, a Cl of 94.0 mL/h/kg and V d of 1574.7 mL/kg. Following the last p.o. administration the baseline plasma concentration was 537.5 ± 268.4 and increased to 1302.6 ± 925.0 pg/mL at 0.25 h, and declined to 18.9 ± 7.4 pg/mL at 96 h. CLB was still quantifiable in urine at 288 h following the last administration (210.0 ± 110 pg/mL). The difference between plasma and urinary concentrations of CLB was 100‐fold irrespective of the route of administration. This 100‐fold urine/plasma difference should be considered when the presence of CLB in urine is reported by equine forensic laboratories.