title: Methadone in healthy goats - pharmacokinetics, behaviour and blood pressure.
abstract: The pharmacokinetics and effects of the opioid methadone on behaviour, arterial blood pressure, heart rate and haematocrit were studied in goats. Two goats received methadone (0.2mg/kg) intravenously and the terminal half-life was 88 and 91 min, the volume of distribution 8.4 and 6.1L/kg, and clearance 86 and 123 mL/min/kg. In a crossover study eight goats received methadone (0.6 mg/kg) or 0.15M NaCl subcutaneously (SC). After SC administration bioavailability was complete and the terminal half-life was 215 ± 84 min (mean ± SD), Tmax 31 ± 15 min and Cmax 45 ±11 ng/mL. Blood pressure and haematocrit increased while heart rate did not change. The goats did not ruminate and they climbed, scratched, gnawed and showed tail-flicking after SC methadone in contrast to NaCl administration. The use of methadone in goats may be restricted due to the inhibition of rumination and the rather short half-life.
authors.affiliation: Division of Pharmacology and Toxicology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden. lena.olsen@slu.se
authors.forename: L
authors.initials: L
authors.lastname: Olsén
authors.forename: K
authors.initials: K
authors.lastname: Olsson
authors.forename: E
authors.initials: E
authors.lastname: Hydbring-Sandberg
authors.forename: U
authors.initials: U
authors.lastname: Bondesson
authors.forename: C
authors.initials: C
authors.lastname: Ingvast-Larsson
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics; D000818:Animals; D019540:Area Under Curve; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D018592:Cross-Over Studies; D005260:Female; D006041:Goats / Q000378:metabolism*; D006207:Half-Life; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006400:Hematocrit / Q000662:veterinary; D008691:Methadone / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*; D010865:Pilot Projects; D011897:Random Allocation
chemical_list: D000701:Analgesics, Opioid; D008691:Methadone