title: Pharmacokinetics and pharmacodynamics comparison between subcutaneous and intravenous butorphanol administration in horses.
abstract: The study objective was to compare butorphanol pharmacokinetics and physiologic effects following intravenous and subcutaneous administration in horses. Ten adult horses received 0.1 mg/kg butorphanol by either intravenous or subcutaneous injections, in a randomized crossover design. Plasma concentrations of butorphanol were measured at predetermined time points using highly sensitive liquid chromatography-tandem mass spectrometry assay (LC-MS/MS). Demeanor and physiologic variables were recorded. Data were analyzed with multivariate mixed-effect model on ranks (P ≤ 0.05). For subcutaneous injection, absorption half-life and peak plasma concentration of butorphanol were 0.10 ± 0.07 h and 88 ± 37.4 ng/mL (mean ± SD), respectively. Bioavailability was 87%. After intravenous injection, mean ± SD butorphanol steady-state volume of distribution and clearance was 1.2 ± 0.96 L/kg and 0.65 ± 0.20 L/kg/h, respectively. Terminal half-lives for butorphanol were 2.31 ± 1.74 h and 5.29 ± 1.72 h after intravenous and subcutaneous administrations. Subcutaneous butorphanol reached and maintained target plasma concentrations >10 ng/mL for 2 ± 0.87 h (Mean ± SD), with less marked physiologic and behavioral effects compared to intravenous injection. Subcutaneous butorphanol administration is an acceptable alternative to the intravenous route in adult horses.
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: L
authors.initials: L
authors.lastname: Chiavaccini
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Claude
authors.affiliation: Department of Basic Sciences, Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Basic Sciences, Center for Environmental Health Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: Ross
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Meyer
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS, USA.
authors.forename: V C
authors.initials: VC
authors.lastname: Langston
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D000818:Animals; D001682:Biological Availability; D002077:Butorphanol / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D018592:Cross-Over Studies; D005260:Female; D006207:Half-Life; D006736:Horses / Q000097:blood*; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008297:Male; D013223:Statistics as Topic
chemical_list: D000701:Analgesics, Opioid; D002077:Butorphanol