Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells

Monolayers of a well differentiated human intestinal epithelial cell line, Caco-2, were used as a model to study passive drug absorption across the intestinal epithelium. Absorption rate constants (expressed as apparent permeability coefficients) were determined for 20 drugs and peptides with different structural properties. The permeability coefficients ranged from approximately 5 × 10−8 to 5 × 10−5 cm/s. A good correlation was obtained between data on aral absorption in humans and the results in the Caco-2 model. Drugs that are completely absorbed in humans had permeability coefficients > 1 × 10−6 cm/s. Drugs that are absorbed to > 1% but < 100% had permeability coefficients of 0.1−1.0 × 10−6 cm/s while drugs and peptides that are absorbed to < 1% had permeability coefficients ≤ 1 × 10−7 cm/s. The results indicate that Caco-2 monolayers can be used as a model for studies on intestinal drug absorption.