Raffa RB, Friderichs E, Reimann W, et al. Complementary and synergistic antinociceptive interaction between the enantiomers of tramadol. J Pharmacol Exp Ther 1993; 267: 331–340.
Wilder-Smith CH, Bettiga A. The analgesic tramadol has minimal effect on gastrointestinal motor function. Br J Clin Pharmacol 1997; 43: 71–75.
Scott LJ, Perry CM. Tramadol: a review of its use in perioperative pain. Drugs 2000; 60: 139–176.
Hennies HH, Friderichs E, Schneider J. Receptor binding, analgesic and antitussive potency of tramadol and other selected opioids. Arzneimittelforschung 1988; 38: 877–880.
Lee CR, McTavish D, Sorkin EM. Tramadol. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in acute and chronic pain states. Drugs 1993; 46: 313–340.
Driessen B, Reimann W. Interaction of the central analgesic, tramadol, with the uptake and release of 5-hydroxytryptamine in the rat brain in vitro. Br J Pharmacol 1992; 105: 147–151.
Sevcik J, Nieber K, Driessen B, et al. Effects of the central analgesic tramadol and its main metabolite, O-desmethyltramadol, on rat locus coeruleus neurones. Br J Pharmacol 1993; 110: 169–176.
Poulsen L, Arendt-Nielsen L, Brosen K, et al. The hypoalgesic effect of tramadol in relation to CYP2D6. Clin Pharmacol Ther 1996; 60: 636–644.
Halfpenny DM, Callado LF, Hopwood SE, et al. Effects of tramadol stereoisomers on norepinephrine efflux and uptake in the rat locus coeruleus measured by real time voltammetry. Br J Anaesth 1999; 83: 909–915.
Nakamura M, Minami K, Uezono Y, et al. The effects of the tramadol metabolite O-desmethyl tramadol on muscarinic receptor-induced responses in Xenopus oocytes expressing cloned M1 or M3 receptors. Anesth Analg 2005; 101: 180–186.
Kirchheiner J, Keulen JT, Bauer S, et al. Effects of the CYP2D6 gene duplication on the pharmacokinetics and pharmacodynamics of tramadol. J Clin Psychopharmacol 2008; 28: 78–83.
KuKanich B, Papich MG. Pharmacokinetics of tramadol and the metabolite O-desmethyltramadol in dogs. J Vet Pharmacol Ther 2004; 27: 239–246.
McMillan CJ, Livingston A, Clark CR, et al. Pharmacokinetics of intravenous tramadol in dogs. Can J Vet Res 2008; 72: 325–331.
Giorgi M, Del Carlo S, Saccomanni G, et al. Pharmacokinetics of tramadol and its major metabolites following rectal and intravenous administration in dogs. N Z Vet J 2009; 57: 146–152.
Giorgi M, Saccomanni G, Lebkowska-Wieruszewska B, et al. Pharmacokinetic evaluation of tramadol and its major metabolites after single oral sustained tablet administration in the dog: a pilot study. Vet J 2009; 180: 253–255.
Giorgi M, Del Carlo S, Saccomanni G, et al. Pharmacokinetics and urine profile of tramadol and its major metabolites following oral immediate release capsules administration in dogs. [published online ahead of print Jun 16, 2009]. Vet Res Commun doi:10.1007/s11259–009–9236–1.
KuKanich B, Lascelles BD, Papich MG. Use of a von Frey device for evaluation of pharmacokinetics and pharmacodynamics of morphine after intravenous administration as an infusion or multiple doses in dogs. Am J Vet Res 2005; 66: 1968–1974.
KuKanich B, Lascelles BD, Papich MG. Assessment of a von Frey device for evaluation of the antinociceptive effects of morphine and its application in pharmacodynamic modeling of morphine in dogs. Am J Vet Res 2005; 66: 1616–1622.
Stamer UM, Lehnen K, Höthker F, et al. Impact of CYP2D6 genotype on postoperative tramadol analgesia. Pain 2003; 105: 231–238.
Grond S, Meuser T, Uragg H, et al. Serum concentrations of tramadol enantiomers during patient-controlled analgesia. Br J Clin Pharmacol 1999; 48: 254–257.
Lehmann KA, Kratzenberg U, Schroeder-Bark B, et al. Postoperative patient-controlled analgesia with tramadol: analgesic efficacy and minimum effective concentrations. Clin J Pain 1990; 6: 212–220.
Desmeules JA, Piguet V, Collart L, et al. Contribution of monoaminergic modulation to the analgesic effect of tramadol. Br J Clin Pharmacol 1996; 41: 7–12.
Xie H, Dong ZQ, Ma F, et al. Involvement of serotonin 2A receptors in the analgesic effect of tramadol in mono-arthritic rats. Brain Res 2008; 1210: 76–83.
Wu WN, McKown LA, Gauthier AD, et al. Metabolism of the analgesic drug, tramadol hydrochloride, in rat and dog. Xenobiotica 2001; 31: 423–441.
Advertisement
Objective—To determine the pharmacokinetics of tramadol, the active metabolite O-desmethyltrcamadol, and the metabolites N-desmethyltramadol and N,O-didesmethyltramadol after oral tramadol administration and to determine the antinociceptive effects of the drug in Greyhounds.
Animals—6 healthy 2- to 3-year-old Greyhounds (3 male and 3 female), weighing 25.5 to 41.1 kg.
Procedures—A mean dose of 9.9 mg of tramadol HCl/kg was administered PO as whole tablets. Blood samples were obtained prior to and at various points after administration to measure plasma concentrations of tramadol and its metabolites via liquid chromatography with mass spectrometry. Antinociceptive effects were determined by measurement of pain-pressure thresholds with a von Frey device.
Results—Tramadol was well tolerated, and a significant increase in pain-pressure thresholds was evident 5 and 6 hours after administration. The mean maximum plasma concentrations of tramadol, O-desmethyltramadol, N-desmethyltramadol, and N,O-didesmethyltramadol were 215.7, 5.7, 379.1, and 2372 ng/mL, respectively. The mean area-under-the-curve values for the compounds were 592, 16, 1,536, and 1,013 h·ng/mL, respectively. The terminal half-lives of the compounds were 1.1, 1.4, 2.3, and 3.6 hours, respectively. Tramadol was detected in urine 5 days, but not 7 days, after administration.
Conclusions and Clinical Relevance—Oral tramadol administration yielded antinociceptive effects in Greyhounds, but plasma concentrations of tramadol and O-desmethyltramadol were lower than expected. Compared with the approved dose (100 mg, PO) in humans, a mean dose of 9.9 mg/kg, PO resulted in similar tramadol but lower O-desmethyltramadol plasma concentrations in Greyhounds.
Supported primarily by the Kansas Racing and Gaming Commission and by the Department of Anatomy and Physiology, Kansas State University, the Merck-Merial Veterinary Scholar Program, and the National Institutes of Health (NIH T35RR007064).
The authors thank Racheal Cohen and Megan Montgomery for technical assistance.