1. Raffa RB, Friderichs E, Reimann W, et al. Opioid and nonopioid components independently contribute to the mechanism of action of tramadol, an “atypical” opioid analgesic. J Pharmacol Exp Ther 1992; 260: 275–285.
2. Raffa RB, Friderichs E, Reimann W, et al. Complimentary and synergistic antinociceptive interaction between the enantiomers of tramadol. J Pharmacol Exp Ther 1993; 267: 331–340.
3. Stamer UM, Lehnen K, Hothker F, et al. Impact of CYP2D6 genotype on postoperative analgesia. Pain 2003; 105: 231–238.
4. Gillen C, Haurand M, Kobelt DJ, et al. Affinity, potency and efficacy of tramadol and its metabolites at the cloned human mu-opioid receptor. Naunyn Schmiedebergs Arch Pharmacol 2000; 362: 116–121.
5. Giorgi M, Del Carlo S, Saccomanni G, et al. Pharmacokinetics and urine profile of tramadol and its major metabolites after oral immediate release capsule administration in the dog. Vet Res Commun 2009; 33: 875–885.
6. 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. Vet J 2009; 180: 253–255.
7. KuKanich B, Papich MG. Pharmacokinetics and antinociceptive effects of oral tramadol hydrochloride administration in Greyhounds. Am J Vet Res 2011; 72: 256–262.
8. KuKanich B, Papich MG. Pharmacokinetics of tramadol and the metabolite O-desmethyltramadol in dogs. J Vet Pharmacol Ther 2004; 27: 239–246.
9. Cone EJ, Darwin WD, Gorodetzky CW, et al. Comparative metabolism of hydrocodone in man, rat, guinea pig, rabbit, and dog. Drug Metab Dispos 1978; 6: 488–493.
10. KuKanich B, Spade J. Pharmacokinetics of hydrocodone and hydromorphone after oral hydrocodone in healthy Greyhound dogs. Vet J 2013; 196: 266–268.
11. Wegner K, Horais KA, Tozier NA, et al. Development of a canine nociceptive thermal escape model. J Neurosci Methods 2008; 168: 88–97.
12. Guedes AG, Papich MG, Rude EP, et al. Pharmacokinetics and physiological effects of intravenous hydromorphone in conscious dogs. J Vet Pharmacol Ther 2008; 31: 334–343.
13. Benitez ME, Roush JK, McMurphy R, et al. Clinical efficacy of hydrocodone-acetaminophen and tramadol for control of postoperative pain in dogs following tibial plateau leveling osteotomy. Am J Vet Res 2015; 76: 755–762.
14. Slocum B, Slocum TD. Tibial plateau levelling osteotomy for repair of cranial cruciate ligament rupture in the canine. Vet Clin North Am Small Anim Pract 1993; 23: 777–795.
15. Reid J, Nolan AM, Hughes JM, et al. Development of the short-form Glasgow composite measure of pain scale and derivation of an analgesic intervention score. Anim Welf 2007; 12: 97–104.
16. Findlay JW, Jones EC, Welch RM. Radioimmunoassay determination of the absolute oral bioavailabilities and O-demethylation of codeine and hydrocodone in the dog. Drug Metab Dispos 1979; 7: 310–314.
17. Li AC, Chovan JP, Yu E, et al. Update on hydrocodone metabolites in rats and dogs aided with a semi-automatic software for metabolite identification Mass-MetaSite. Xenobiotica 2013; 43: 390–398.
18. Wu WN, McKowen LA, Gauthier AD, et al. Metabolism of analgesic drug, tramadol hydrochloride, in rat and dog. Xenobiotica 2001; 31: 423–441.
19. 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.
20. 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.
21. 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.
Advertisement
OBJECTIVE To evaluate the pharmacokinetics of hydrocodone (delivered in combination with acetaminophen) and tramadol in dogs undergoing tibial plateau leveling osteotomy (TPLO).
ANIMALS 50 client-owned dogs.
PROCEDURES Dogs were randomly assigned to receive tramadol hydrochloride (5 to 7 mg/kg, PO, q 8 h; tramadol group) or hydrocodone bitartrate–acetaminophen (0.5 to 0.6 mg of hydrocodone/kg, PO, q 8 h; hydrocodone group) following TPLO with standard anesthetic and surgical protocols. Blood samples were collected for pharmacokinetic analysis of study drugs and their metabolites over an 8-hour period beginning after the second dose of the study medication.
RESULTS The terminal half-life, maximum serum concentration, and time to maximum serum concentration for tramadol following naïve pooled modeling were 1.56 hours, 155.6 ng/mL, and 3.90 hours, respectively. Serum concentrations of the tramadol metabolite O-desmethyltramadol (M1) were low. For hydrocodone, maximum serum concentration determined by naïve pooled modeling was 7.90 ng/mL, and time to maximum serum concentration was 3.47 hours. The terminal half-life for hydrocodone was 15.85 hours, but was likely influenced by delayed drug absorption in some dogs and may not have been a robust estimate. Serum concentrations of hydromorphone were low.
CONCLUSIONS AND CLINICAL RELEVANCE The pharmacokinetics of tramadol and metabolites were similar to those in previous studies. Serum tramadol concentrations varied widely, and concentrations of the active M1 metabolite were low. Metabolism of hydrocodone to hydromorphone in dogs was poor. Further study is warranted to assess variables that affect metabolism and efficacy of these drugs in dogs.