title: Effects of subcutaneous methadone, morphine, buprenorphine or saline on thermal and pressure thresholds in cats.
abstract: This study compared pressure and thermal thresholds after administration of three opioids in eight cats. Pressure stimulation was performed via a bracelet taped around the forearm. Three ball-bearings were advanced against the forearm by inflation of a modified blood pressure bladder. Pressure in the cuff was recorded at the end point (leg shake and head turn). Thermal threshold was tested as previously reported using a heated probe held against the thorax [Dixon et al. (2002) Research in Veterinary Science, 72, 205]. After baseline recordings, each cat received subcutaneous methadone 0.2 mg/kg, morphine 0.2 mg/kg, buprenorphine 0.02 mg/kg or saline 0.3 mL in a four period cross-over study. Measurements were made at 15, 30, 45 min and 1, 2, 3, 4, 8, 12 and 24 h after the injection. Data were analysed by anova (P<0.05). There were no significant changes in thresholds after saline. Thermal threshold increased at 45 min after buprenorphine (maximum 2.8+/-3 degrees C), 1-3 h after methadone (maximum 3.4+/-1.9 degrees C) and 45 min to 1 h (maximum 3.4+/-2 degrees C) after morphine. Pressure threshold increased 30-45 min (maximum 238+/-206 mmHg) after buprenorphine, 45-60 min after methadone (maximum 255+/-232 mmHg) and 45-60 min and 3-6 h (maximum 255+/-232 mmHg) after morphine. Morphine provided the best analgesia, and methadone appears a promising alternative. Buprenorphines limited effect was probably related to the subcutaneous route of administration. Previously, buprenorphine has produced much greater effects when given by other routes.
authors.affiliation: Faculty of Veterinary Medicine and Animal Science, FMVZ, Unesp, Botucatu, SP, Brazil. pvms2001@yahoo.com.br
authors.forename: P V M
authors.initials: PV
authors.lastname: Steagall
authors.forename: P
authors.initials: P
authors.lastname: Carnicelli
authors.forename: P M
authors.initials: PM
authors.lastname: Taylor
authors.forename: S P L
authors.initials: SP
authors.lastname: Luna
authors.forename: M
authors.initials: M
authors.lastname: Dixon
authors.forename: T H
authors.initials: TH
authors.lastname: Ferreira
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage / Q000494:pharmacology; D002415:Cats; D005260:Female; D006358:Hot Temperature; D007279:Injections, Subcutaneous / Q000662:veterinary; D008297:Male; D008691:Methadone / Q000008:administration & dosage / Q000494:pharmacology; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D010146:Pain / Q000517:prevention & control / Q000662:veterinary*; D010147:Pain Measurement / Q000187:drug effects / Q000662:veterinary*; D011312:Pressure
chemical_list: D000701:Analgesics, Opioid; D002047:Buprenorphine; D009020:Morphine; D008691:Methadone