title: Plasma fentanyl concentrations in awake cats and cats undergoing anesthesia and ovariohysterectomy using transdermal administration.
abstract: OBJECTIVE
  To measure the plasma fentanyl concentrations achieved over time with transdermal fentanyl patches in awake cats and cats undergoing anesthesia and ovariohysterectomy.
  
  
  METHODS
  Randomized prospective experimental study.
  
  
  METHODS
  Twenty-four purpose-bred cats.
  
  
  METHODS
  Cats were randomly assigned to three groups for Part I of a larger concurrent study. Group P received only a 25 micro g hour-1 transdermal fentanyl patch. Group P/A received the patch and anesthesia. Group A received only anesthesia. After a minimum 1-week washout period, the cats were randomly reassigned to two groups for Part II of the larger study. Group P/A/O received the patch, anesthesia and ovariohysterectomy. Group A/O received anesthesia and ovariohysterectomy. Patches were left in place for 72 hours and plasma samples were obtained for fentanyl analysis while the patches were in place, and for 8 hours after patch removal for cats in Group P, P/A, and P/A/O.
  
  
  RESULTS
  The 25 micro g hour-1 transdermal fentanyl patches were well tolerated by the cats in this study (mean body weight of 3.0 kg) and no overt adverse effects were noted. Mean plasma fentanyl concentrations over time, mean plasma fentanyl concentrations at specific times (8, 25, 49, and 73 hours after patch placement), time to first detectable plasma fentanyl concentration, time to reach maximum plasma fentanyl concentration, maximum plasma fentanyl concentration, mean plasma fentanyl concentration from 8 to 73 hours, elimination half-life, and total area under concentration (AUC) were not statistically different among the groups.
  
  
  CONCLUSIONS
  Halothane anesthesia and anesthesia/ovariohysterectomy did not significantly alter the plasma fentanyl concentrations achieved or pharmacokinetic parameters measured, when compared with awake cats. There was a high degree of individual variability observed both within and between groups of cats in parameters measured.
  
  
  CONCLUSIONS
  The high degree of variability observed suggests that careful observation of cats with fentanyl patches in place is required to assess efficacy and any potential adverse effects. Anesthesia and anesthesia/ovariohysterectomy do not appear to alter plasma fentanyl concentrations achieved by placement of a 25 micro g hour-1 transdermal fentanyl patch when compared to cats not undergoing these procedures.
authors.affiliation: Department of Small Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA. cegger@cvm.vet.uga.edu
authors.forename: Christine M
authors.initials: CM
authors.lastname: Egger
authors.forename: Leigh E
authors.initials: LE
authors.lastname: Glerum
authors.forename: Sheila W
authors.initials: SW
authors.lastname: Allen
authors.forename: Michelle
authors.initials: M
authors.lastname: Haag
mesh_terms: D000279:Administration, Cutaneous; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000758:Anesthesia / Q000662:veterinary; D000818:Animals; D019540:Area Under Curve; D001522:Behavior, Animal; D002415:Cats / Q000502:physiology* / Q000601:surgery; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D007044:Hysterectomy / Q000662:veterinary; D010052:Ovariectomy / Q000662:veterinary; D010146:Pain / Q000517:prevention & control / Q000662:veterinary; D010147:Pain Measurement / Q000662:veterinary; D011446:Prospective Studies; D014851:Wakefulness
chemical_list: D000701:Analgesics, Opioid; D005283:Fentanyl