Pharmaceutical formulations containing natural and/or synthetic lipids are an accepted strategy for potentially improving the oral bioavailability and systemic exposure of poorly water soluble, ...highly lipophilic drug candidates. For example, lipid-based formulations are commercially available for various drugs including cyclosporine, saquinavir, ritonavir, dutasteride and amprenavir. Consequently, lipid-based systems are often considered when needing to increase drug exposure during pre-clinical drug development.
Orally administered drugs may gain access to the systemic circulation via absorption into the portal blood or by transport through the intestinal lymphatic system. In the majority of cases, ...absorption via the portal blood is the predominant pathway as portal blood flow, relative to intestinal lymph flow, is orders of magnitude higher (approximately 500-fold). However, for some highly lipophilic compounds, their association and interaction with enterocyte-derived lymph lipoproteins may be sufficient to overcome the differences in relative blood/lymph flow rates resulting in the lymphatics becoming a quantitatively important drug transport pathway.
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