Effects of oral dosing paradigms (gavage versus diet) on pharmacokinetics and pharmacodynamics

In cancer chemopreventive studies, test agents are typically administered via diet, while the preclinical safety studies normally employ oral gavage dosing. Correspondence in pharmacokinetic and pharmacodynamic profiles between the two dosing approaches cannot be assumed a priori. Sulindac, a non-steroidal anti-inflammatory agent with potential chemopreventive activity, was used to assess effects of the two oral dosing paradigms on its pharmacokinetics and pharmacodynamics. Time-dependent concentrations of sulindac and its sulfone metabolite were determined in plasma and potential target organ, mammary gland. Prostaglandin E2 was used as a pharmacodynamic biomarker and measured in mammary gland. An inverse linear relationship was detected between pharmacodynamic and pharmacokinetic markers, area under the curve for prostaglandin E2 levels and sulindac sulfone concentrations, respectively, in the mammary tissue. Marked differences in pharmacokinetics and pharmacodynamics were observed after administration of sulindac by the two oral dosing paradigms. In general, oral gavage resulted in higher peak and lower trough concentrations of sulindac in plasma and mammary tissue, higher area under concentration–time curve in plasma and mammary tissue, and greater effect on prostaglandin E2 levels than the corresponding diet dosing. This study illustrates potential pitfalls and limitations in trying to generalize based on data obtained with different oral dosing schemes and their extrapolation to potential efficacy and health risks in humans.