title: Plasma pharmacokinetics of ranitidine HCl in adult horses.
abstract: Plasma pharmacokinetics of ranitidine HCl were investigated after intravenous (i.v.) and oral (p.o.) administration of 2.2 mg/kg drug to six healthy adult horses. Concentrations of ranitidine were determined using normal-phase, high-performance liquid chromatography. Plasma concentrations of ranitidine HCl declined from a mean of 5175 ng/mL at 5 min to 37 ng/mL at 720 min after i.v. administration. A three-exponent equation, Cp = A1 x e-k1t + A2 x e-k2t + A3 x e-k3t, best described data for all horses. Mean values for model-independent values calculated from the last quantifiable time point were: apparent volume of distribution (Vdss) = 1.07 L/kg; area under the curve (AUC) = 231,000 ng.min/mL: area under the moment curve (AUMC) = 26,900,000 ng.min2/mL; mean residence time (MRT) = 113 min; and clearance (Cl) = 9.8 mL/min.kg. Following p.o. administration, a two-exponent equation, Cp = A1 x e-k1t + A2 x e-k2t, best described the data for five horses: data for the remaining horse were best described by a three-exponent equation. Mean values of pharmacokinetic values from the p.o. study include: AUC = 59,900 ng x min/mL; AUMC = 10,600,000 ng x min2/mL; mean absorption time (MAT) = 58.9 min: Tmax = 99.2 min; Cmax = 237 ng/mL: and F = 27%.
authors.affiliation: Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University, College Station 77843-4475, USA.
authors.forename: P S
authors.initials: PS
authors.lastname: Holland
authors.forename: W W
authors.initials: WW
authors.lastname: Ruoff
authors.forename: G W
authors.initials: GW
authors.lastname: Brumbaugh
authors.forename: S A
authors.initials: SA
authors.lastname: Brown
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006736:Horses / Q000097:blood*; D007275:Injections, Intravenous; D008297:Male; D008954:Models, Biological; D011899:Ranitidine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D011899:Ranitidine