Pharmacokinetics and efficacy of intravenous and extradural tramadol in dogs

Tramadol is a synthetic opioid agonist used extensively in human and, to a lesser extent, veterinary medicine throughout the world. The clinical efficacy and pharmacokinetic profile of intravenous (IV) and extradural (ED) tramadol (2 mg/kg) and its o-desmethyl metabolite were studied in dogs undergoing tibial plateau levelling osteotomy (TPLO). Intra-operative cardiorespiratory variables were monitored and post-operative pain was assessed using the short form of the Glasgow Composite Pain Scale. A rapid (<5 min) and effective production of o-desmethyl tramadol was recorded. The pharmacokinetic profile was similar for tramadol and its metabolite irrespective of the route of administration. ED tramadol provided sufficient intra- and post-operative analgesia without significant clinical side-effects, but the post-operative analgesia was comparable to that following IV administration and the ED route could therefore not be considered a practical alternative to the IV route.