title: The pharmacology and pharmacokinetics of high-dose methocarbamol in horses.
abstract: The haemodynamic, respiratory and behavioural effects and pharmacokinetics of methocarbamol were studied in eight healthy, adult horses after intravenous (i.v.) and oral administration of large dosages. Heart rate, cardiac output, mean pulmonary arterial blood pressure, systolic, diastolic and mean aortic blood pressure, respiratory rate and arterial blood gases did not change after either i.v. (30 mg/kg bodyweight [bwt]) or oral (50 and 100 mg/kg bwt) dosages of methocarbamol. Mild to moderate depression was observed in five of eight horses administered i.v. methocarbamol, and in all horses administered oral methocarbamol. Plasma methocarbamol concentration declined very rapidly during the initial or rapid disposition phase after i.v. administration; the terminal elimination half-life ranged from 59 to 90 mins. Peak plasma methocarbamol concentrations following oral administration occurred within 15 to 45 mins and oral bioavailability ranged from 50.7 to 124 percent.
authors.affiliation: Department of Veterinary Clinical Sciences, Ohio State University, Columbus 43210-1089, USA.
authors.forename: W W
authors.initials: WW
authors.lastname: Muir
authors.forename: R A
authors.initials: RA
authors.lastname: Sams
authors.forename: S
authors.initials: S
authors.lastname: Ashcraft
mesh_terms: D000284:Administration, Oral; D000827:Animal Welfare; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D003863:Depression / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D006140:Guaifenesin / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000378:metabolism / Q000502:physiology*; D007275:Injections, Intravenous / Q000662:veterinary; D008721:Methocarbamol / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D009125:Muscle Relaxants, Central / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology*; D011669:Pulmonary Wedge Pressure / Q000187:drug effects; D012119:Respiration / Q000187:drug effects
chemical_list: D009125:Muscle Relaxants, Central; D008721:Methocarbamol; D006140:Guaifenesin