Plasma pharmacokinetics of ranitidine HCl in foals.
Plasma pharmacokinetics of ranitidine HCl were investigated after intravenous (i.v.) and oral (p.o.) administration of drug to six healthy foals. Twelve- to sixteen-week-old foals received 2.2 mg ranitidine/kg i.v. and 4.4 mg ranitidine/kg p.o. Concentrations of ranitidine were determined using normal phase high performance liquid chromatography. Plasma concentrations of ranitidine HCl declined from a mean of 3266 ng/mL at 5 min to 11 ng/mL at 720 min after administration. The profile of the plot of concentrations of ranitidine HCl vs. time was best described by a two-exponent equation for two foals; data for the remaining four foals were best described by a three-exponent equation. Mean values for model-independent values were: apparent volume of distribution (Vdss) = 1.46 L/kg; area under the curve (AUC) = 167,442 ng.min/mL; area under the moment curve (AUMC) = 18,068,221 ng.min2/mL; mean residence time (MRT) = 108.9 min; and clearance (Cl) = 13.3 mL/min.kg. Following p.o. administration, a two-exponent equation best described data for five foals; data for the remaining foal were best described by a three-exponent equation. Mean values of the pharmacokinetic values from the p.o. study include: AUC = 126,413 ng.min/mL; AUMC = 18,039,825 ng.min2/mL; mean absorption time (MAT) = 32.0 min; observed time to maximum plasma concentration (Tmax) = 57.2 min; maximum observed plasma concentration (Cmax) = 635.7 ng/mL; and bioavailability (F) = 38%.
Holland
P S
PS
Department of Large Animal Medicine and Surgery, College of Veterinary Medicine, Texas A&M University College Station 77843-4475, USA.
Brumbaugh
G W
GW
Ruoff
W W
WW
Brown
S A
SA
D000284:Administration, Oral; D000818:Animals; D000897:Anti-Ulcer Agents / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*; D019540:Area Under Curve; D005260:Female; D006736:Horses; D007275:Injections, Intravenous; D008297:Male; D011899:Ranitidine / Q000008:administration & dosage / Q000097:blood* / Q000493:pharmacokinetics*
D000897:Anti-Ulcer Agents; D011899:Ranitidine