Mathematical modeling of oral absorption and bioavailability of a fluoroquinolone after its precipitation in the gastrointestinal tract

Abstract

1. The objective was to characterize the in vivo absorption and bioavailability (BA) of a low solubility, high permeability fluoroquinolone (CNV97101) that precipitates in the gastrointestinal (GI) tract by mathematical modeling approach.

2. In situ rat intestinal perfusion studies were performed to characterize the absorption mechanism. The oral fraction absorbed in vivo was lower than the predicted based on the in situ intestinal permeability. Two additional routes of administration, intraduodenal (ID) and intraperitoneal (IP) were investigated to explore if precipitation in stomach and subsequent partial re-dissolution were the causes of the lower in vivo BA. Ex vivo precipitation studies with the stomach content of fasted rats were also carried out. Fitting procedures were performed with NONMEM VII 1.2.

3. The in situ experiments confirmed simultaneous passive and carrier-mediated absorption processes. The ex vivo experiments confirmed precipitation in stomach lowering in vivo the oral fraction absorbed compared with the IP and ID administrations. Due to the almost complete availability of CNV97101 following IP administration, a first hepatic pass could be excluded. The ex vivo assay results and the pharmacokinetic modeling of in vivo data supported the hypothesis of precipitation in the stomach and partial re-dissolution. Nevertheless, other factors such as residence time in the GI may reduce the fraction absorbed even for low oral doses for which re-dissolution was almost complete in vivo.

• Absorption modeling
• ADME optimization
• bioavailability
• intestinal absorption
• pharmacokinetics