In monkeys, dogs and swine (six each) we tested the reduction of the isoflurane MAC (minimal alveolar concentration) produced by 2 mg‐kg‐1 morphine intravenously (i‐v.) and the concurrent effect on Pco2 with spontaneous ventilation. MAC fell to a minimum of 55% of control at 53 min in monkeys, 50% at 38 min in dogs and 13% at 33 min in swine. Paco2 rose at constant MAC with morphine to 55–60 mmHg, but did not fall over the next several hours despite the decline of plasma morphine concentration, and the resulting needed rise in isoflurane concentration to keep the anaesthesia depth at 1 MAC. After isoflurane concentration had returned to pre‐morphine control levels, naloxone immediately reduced Paco2 to or below control level. Morphine pharmacokinetics in the three species studied conformed to a two‐compartment model.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Veterinary Pharmacology and Therapeutics|
|State||Published - Jan 1 1994|
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