Effect of orally administered tramadol alone or with an intravenously administered opioid on minimum alveolar concentration of sevoflurane in cats

Abstract

OBJECTIVE-To compare the effect of oral administration of tramadol alone and with IV administration of butorphanol or hydromorphone on the minimum alveolar concentration (MAC) of sevoflurane in cats. DESIGN-Crossover study. ANIMALS-8 Healthy 3-year-old cats. PROCEDURES-Cats were anesthetized with sevoflurane in 100% oxygen. A standard tail clamp method was used to determine the MAC of sevoflurane following administration of tramadol (8.6 to 11.6 mg/kg [3.6 to 5.3 mg/lb], PO, 5 minutes before induction of anesthesia), butorphanol (0.4 mg/kg [0.18 mg/lb], IV, 30 minutes after induction), hydromorphone (0.1 mg/kg [0.04 mg/lb], IV, 30 minutes after induction), saline (0.9% NaCl) solution (0.05 mL/kg [0.023 mL/lb], IV, 30 minutes after induction), or tramadol with butorphanol or with hydromorphone (same doses and routes of administration). Naloxone (0.02 mg/kg [0.009 mg/lb], IV) was used to reverse the effects of treatments, and MACs were redetermined. RESULTS-Mean +/- SEM MACs for sevoflurane after administration of tramadol (1.48 +/- 0.20%), butorphanol (1.20 +/- 0.16%), hydromorphone (1.76 +/- 0.15%), tramadol and butorphanol (1.48 +/- 0.20%), and tramadol and hydromorphone (1.85 +/- 0.20%) were significantly less than those after administration of saline solution (2.45 +/- 0.22%). Naloxone reversed the reductions in MACs. CONCLUSIONS AND CLINICAL RELEVANCE-Administration of tramadol, butorphanol, or hydromorphone reduced the MAC of sevoflurane in cats, compared with that in cats treated with saline solution. The reductions detected were likely mediated by effects of the drugs on opioid receptors. An additional reduction in MAC was not detected when tramadol was administered with butorphanol or hydromorphone.

Evaluation of the analgesic effects of oral and subcutaneous tramadol administration in red-eared slider turtles

“…33 Larger tramadol doses ranging between 11 and 80 mg/kg (5.0 and 36.36 mg/lb) were used safely for studies in cats and rodents. 13,34 Because of limited clinical experience with tramadol in reptiles, a wide range of doses (1 to 25 mg/kg) were used in the present study to test antinociception in turtles. In mammals, the analgesic effects of tramadol typically begin within 30 minutes and last for 6 hours.…”

Effect of intravenous administration of tramadol hydrochloride on the minimum alveolar concentration of isoflurane in rabbits

“…The transient hypotension (SAP, approx 60 mm Hg) that was evident in 3 rabbits immediately after tramadol administration was unlikely to have affected the MAC. 19 The studies 17,19 in rats and cats involved the tail-clamping technique as the noxious stimulus, but plasma tramadol and M1 concentrations were not reported. 14,26 In the rabbits of the study reported here, IV administration of tramadol at a dose of 4.4 mg/kg resulted in mean plasma tramadol and M1 concentrations of 346 ng/mL and 41 ng/mL, respectively, and a reduction in ISOMAC of 9%, compared with the value before tramadol administration.…”

“…In another study 16 involving dogs, when tramadol was administered via a constant rate IV infusion of 1.3 mg/kg/h or 2.6 mg/kg/h, the resulting plasma concentrations of tramadol (2,201 ± 1,552 ng/mL and 4,446 ± 3,875 ng/mL, respectively) and M1 (57 ± 18 ng/mL and 86 ± 20 ng/mL, respectively) caused a reduction in ISOMAC of 26% to 36% when a noxious electrical stimulus was used, although this change was not correlated with plasma tramadol or M1 concentration. 17,19 The M1 metabolite reportedly has a considerable analgesic effect in humans attributable to its action at opioid receptors, 2 but there are several tramadol metabolites that could be responsible for its ISOMAC-lowering effects. Administration of a constant rate infusion of tramadol following the bolus injection may have reduced some of this variability.…”

“…It is a measure of the potency of a volatile anesthetic and can be used to compare the efficacy of analgesic and anesthetic drugs. 19 To the authors' knowledge, the analgesic or MAC-reducing effects of tramadol in rabbits have not been reported. Whereas SC administration of tramadol does not appear to increase the pressure and thermal thresholds in awake cats, 18 oral administration reduces the MAC of sevoflurane in the same species.…”

Determination of the sevoflurane sparing effect of methadone in cats

“…2004; Ferreira et al. 2009) and hydromorphone, tramadol and butorphanol decrease the MAC of sevoflurane (Ko et al. 2008).…”