Example Reducing Carcinogenicity by Decreasing Oral Bioavailability

1 Example Reducing Carcinogenicity by Decreasing Oral Bioavailability 

If we consider mammals other than humans, many variations of these rules can exist due to interspecies differences (e.g., the drug nadolol is absorbed orally significantly more by dogs than by humans and rats). Inter-species differences among mammals are often due to differences in the pH of the GI tract, and also differences in the number, nature, and distribution of intestinal microbes. 

Un-ionized form of organic compounds are generally absorbed more easily, with the exception of nanoparticles. Presence of substituents that remain ionized at pH 2, such as —S03, make chemicals too polar to cross the intestinal membrane 

High logP0/w means too lipid soluble to dissolve in GI tract or low logP0/w mean increased water solubility and elimination once absorbed 

Larger particles deposited higher in the respiratory tract are removed in the mucous layer and swallowed, resulting in a GI tract exposure 

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