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Mol Pharm. 2013 Nov 4;10(11):3997-4004. doi: 10.1021/mp400283j. Epub 2013 Aug 20.

Investigation of the rat model for preclinical evaluation of pH-dependent oral absorption in humans.

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  • 1Genentech, Inc., 1 DNA Way, South San Francisco, California 94080, United States.


Many pharmaceutically active compounds are weak electrolytes and are ionizable in the pH range experienced throughout the gastrointestinal tract. Changes in protonation state due to pH changes in the gut can have dramatic effects on solubility, dissolution, and permeation through biological barriers. Preclinical assessment of the pH-dependence of oral absorption is critical for compounds possessing pH-dependent solubility. Here we examine pH-dependent solubility and oral exposure in rat for three model compounds, dasatinib, ketoconazole, and mefenamic acid. Dasatinib and ketoconazole are both weak bases, while mefenamic acid is a carboxylic acid. The effects of gastric pH modulators, pentagastrin and famotidine, were investigated in rat PK studies to assess the applicability of using the rat to evaluate the risk of pH-dependent oral exposure for ionizable compounds. Dasatinib showed similar exposure between control and pentagastrin-pretreated groups, and 4.5-fold lower AUC in famotidine-pretreated rats. Ketoconazole showed a 2-fold increase in AUC in pentagastrin-treated rats relative to control, and 4.5-fold lower AUC in famotidine treated rats, relative to the pentagastrin group. Mefenamic acid showed highly similar exposures among control, pentagastrin-pretreated, and famotidine-pretreated groups. The rat model was shown to be useful for compounds displaying pH-dependent solubility and oral absorption that may be affected by gastric pH modulators.

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