Reduction of the sevoflurane minimum alveolar concentration induced by methadone, tramadol, butorphanol and morphine in rats

Abstract

This study aimed to estimate the reduction in the minimum alveolar concentration (MAC) of sevoflurane induced by low and high doses of methadone (5 and 10 mg/kg), tramadol (25 and 50 mg/kg), butorphanol (5 and 10 mg/kg) or morphine (5 and 10 mg/kg) in the rat. A control group received normal saline. Sixty-three adult male Sprague-Dawley rats were anaesthetized with sevoflurane (n = 7 per group). Sevoflurane MAC was then determined before and after intraperitoneal administration of the opioids or saline. The duration of the sevoflurane MAC reduction and basic cardiovascular and respiratory measurements were also recorded. The baseline MAC was 2.5 (0.3) vol%. Methadone, tramadol and morphine reduced the sevoflurane MAC (low dose: 31 ± 10, 38 ± 15 and 30 ± 13% respectively; high dose: 100 ± 0, 83 ± 17 and 77 ± 25%, respectively) in a dose-dependent manner. The low and high doses of butorphanol reduced the sevoflurane MAC to a similar extent (33 ± 7 and 31 ± 4%, low and high doses, respectively). Two rats developed apnoea following administration of high-dose butorphanol and methadone. These anaesthetic-sparing effects are clinically relevant and may reduce the adverse effects associated with higher doses of inhalational anaesthetics.

The Effects of the Toll-Like Receptor 4 Antagonist, Ibudilast, on Sevoflurane’s Minimum Alveolar Concentration and the Delayed Remifentanil-Induced Increase in the Minimum Alveolar Concentration in Rats

“…Analgesic treatment with opioids has a major effect on anesthetic requirements by reducing them. 23,24 This reduction can be measured by determining the associated change in the MAC and has clinical relevance. However, the observed changes in the MAC cannot be considered a measure of analgesia but just the interaction of these drugs with inhaled anesthetics.…”

The safety, efficacy and neuromotor effects of the neurosteroid anaesthetic alfaxalone in rats

“…Phenothiazines such as ACP have sedative effects with no analgesic actions and are frequently combined with opioids to improve sedation and analgesia (Monteiro et al, 2009, Monteiro et al, 2008, Flecknell, 1993b. Methadone is an opioid analgesic agent commonly administered in combination with ACP in dogs (Flecknell, 1984, Abreu et al, 2012. Methadone analgesia results from its agonist effect on the mu opioid receptor and its N-methyl-D-aspartate (NMDA) glutamate receptor antagonism (Monteiro et al, 2008, Monteiro et al, 2009.…”

“…Methadone analgesia results from its agonist effect on the mu opioid receptor and its N-methyl-D-aspartate (NMDA) glutamate receptor antagonism (Monteiro et al, 2008, Monteiro et al, 2009. Butorphanol is an opioid analgesic agent, which is a kappa opioid receptor agonist and mild mu opioid receptor antagonist (Abreu et al, 2012). Butorphanol enhances the effects of α 2 -adrenoreceptor agonists, and therefore is often administered in combination with medetomidine (Hayashi et al, 1994).…”

Preanesthesia, Anesthesia, Analgesia, and Euthanasia

“…In addition to buprenorphine, morphine, methadone, tramadol, butorphanol, fentanyl, and remifentanil have been found to reduce the isoflurane and sevoflurane minimum alveolar concentration (MAC) requirements in rats and mice Gómez de Segura, 2000, 2003;Abreu et al, 2012;Smith et al, 2004). Buprenorphine, a partial mu-agonist, is the preferred opioid for rodents as it is more potent than morphine and has a longer duration of action.…”