title: Determination of the sevoflurane sparing effect of methadone in cats.
abstract: OBJECTIVE
  To determine the magnitude and duration of sevoflurane minimum alveolar concentration (MAC) reduction following a single intravenous (IV) dose of methadone in cats.
  
  
  METHODS
  Prospective experimental study.
  
  
  METHODS
  Eight (four females and four males) healthy mixed-breed adult (1-2 years) cats weighing 5.82 ± 0.42 kg.
  
  
  METHODS
  Anesthesia was induced and maintained with sevoflurane. Intravenous catheters facilitated administration of methadone and lactated Ringer's solution. After baseline MAC determination in triplicate using a tail clamp technique, 0.3 mg kg(-1) of methadone was administered IV. End-tidal sevoflurane concentration (e'SEVO) was reduced and MAC was redetermined. In an effort to determine the duration of MAC reduction, measurements were repeated in a stepwise manner until MAC values returned to baseline. After the last stimulation, the e'SEVO was increased to 1.2 individual MAC for 15 minutes, then sevoflurane was discontinued and cats were allowed to recover from anesthesia.
  
  
  RESULTS
  Baseline sevoflurane MAC was 3.18 ± 0.06%. When compared with baseline the sevoflurane MAC after methadone administration was significantly reduced by 25, 15 and 7% at 26, 76 and 122 minutes, respectively. The final MAC value (3.09 ± 0.07%) determined 156 minutes after methadone administration was not significantly different from baseline.
  
  
  CONCLUSIONS
  Intravenous methadone (0.3 mg kg(-1)) significantly decreased MAC of sevoflurane in cats but the effect was short-lived.
authors.affiliation: Department of Anesthesiology, Botucatu Medical School, São Paulo State University - UNESP, Botucatu, SP, Brazil.
authors.forename: Tatiana H
authors.initials: TH
authors.lastname: Ferreira
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Steffey
authors.forename: Khursheed R
authors.initials: KR
authors.lastname: Mama
authors.forename: Marlis L
authors.initials: ML
authors.lastname: Rezende
authors.forename: Antonio J A
authors.initials: AJ
authors.lastname: Aguiar
mesh_terms: D000701:Analgesics, Opioid / Q000097:blood / Q000494:pharmacology*; D000762:Anesthesia Recovery Period; D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D004305:Dose-Response Relationship, Drug; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D008691:Methadone / Q000097:blood / Q000494:pharmacology*; D008738:Methyl Ethers / Q000494:pharmacology*; D009068:Movement / Q000187:drug effects*; D011446:Prospective Studies; D011650:Pulmonary Alveoli; D000077149:Sevoflurane; D013997:Time Factors
chemical_list: D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D008691:Methadone