Plasma pharmacokinetics of ranitidine HCl in adult horses.

This research investigates the plasma pharmacokinetics, or how the drug ranitidine HCl is absorbed, distributed, metabolized, and eliminated in the body, of adult horses after being administered orally and intravenously.

Research Methodology

The research was conducted on six healthy adult horses. Each horse was administered a dose of 2.2 mg/kg of ranitidine HCl both orally and intravenously (IV).

• After these administrations, the concentration of the drug was measured using normal-phase, high-performance liquid chromatography, a technique used to separate the components of a mixture.
• The plasma concentrations of ranitidine HCl were measured at various time intervals, from 5 minutes to 720 minutes post IV administration. The decrease in the concentration of the drug over time was then calculated.
• The research used a three-exponent equation to best describe the flow of the drug in the horses after IV administration.
• The following pharmacokinetic parameters were considered and calculated: apparent volume of distribution (Vdss), area under the curve (AUC), area under the moment curve (AUMC), mean residence time (MRT) and clearance (Cl).

Study Findings

The findings of the research indicated:

• Average decline in the drug value from 5175 ng/mL at 5 minutes post IV administration to 37 ng/mL after 720 minutes.
• Values after calculation for Vdss, AUC, AUMC, MRT and Cl were 1.07 L/kg, 231,000 ng.min/mL, 26,900,000 ng.min2/mL, 113 minutes and 9.8 mL/min.kg respectively.
• In case of oral administration, a two-exponent equation best explained the observations for five horses, while for one horse, a three-exponent equation was more suitable.
• If we look at the pharmacokinetic values from the oral administration study, the AUC, AUMC, mean absorption time (MAT), Tmax, Cmax and F values observed were 59,900 ng x min/mL, 10,600,000 ng x min2/mL, 58.9 min, 99.2 min, 237 ng/mL, and 27% respectively.

These findings can be used to draw conclusions on how different forms of administration affect how the drug is processed in the body of a horse, the information of which could help in determining dosages and intervals for therapeutic treatments involving this drug.