Allison J Stewart, Dawn M Boothe, Crisanta Cruz-Espindola, Emily J Mitchum, Jenny Springfield
Department of Clinical Sciences, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
American journal of veterinary research 2011 JulTo determine the pharmacokinetics of tramadol and its metabolites O-desmethyltramadol (ODT) and N-desmethyltramadol (NDT) in adult horses. 12 mixed-breed horses. Horses received tramadol IV (5 mg/kg, over 3 minutes) and orally (10 mg/kg) with a 6-day washout period in a randomized crossover design. Serum samples were collected over 48 hours. Serum tramadol, ODT, and NDT concentrations were measured via high-performance liquid chromatography and analyzed via noncompartmental analysis. Maximum mean ± SEM serum concentrations after IV administration for tramadol, ODT, and NDT were 5,027 ± 638 ng/mL, 0 ng/mL, and 73.7 ± 12.9 ng/mL, respectively. For tramadol, half-life, volume of distribution, area under the curve, and total body clearance after IV administration were 2.55 ± 0.88 hours, 4.02 ± 1.35 L/kg, 2,701 ± 275 h x ng/mL, and 30.1 ± 2.56 mL/min/kg, respectively. Maximal serum concentrations after oral administration for tramadol, ODT, and NDT were 238 ± 41.3 ng/mL, 86.8 ± 17.8 ng/mL, and 159 ± 20.4 ng/mL, respectively. After oral administration, half-life for tramadol, ODT, and NDT was 2.14 ± 0.50 hours, 1.01 ± 0.15 hours, and 2.62 ± 0.49 hours, respectively. Bioavailability of tramadol was 9.50 ± 1.28%. After oral administration, concentrations achieved minimum therapeutic ranges for humans for tramadol (> 100 ng/mL) and ODT (> 10 ng/mL) for 2.2 ± 0.46 hours and 2.04 ± 0.30 hours, respectively. Duration of analgesia after oral administration of tramadol might be < 3 hours in horses, with ODT and the parent compound contributing equally.
Allison J Stewart, Dawn M Boothe, Crisanta Cruz-Espindola, Emily J Mitchum, Jenny Springfield. Pharmacokinetics of tramadol and metabolites O-desmethyltramadol and N-desmethyltramadol in adult horses. American journal of veterinary research. 2011 Jul;72(7):967-74
PMID: 21728858
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