Mechanism of intestinal absorption of drugs from oil in water emulsions. I.

Mechanism of the absorption of drugs from oil in water emulsions was studied in the rat large intestine. Synthesized esters of fatty acids and phthalic acid-0.1% Polysorbate 80 was chosen as the emulsion system, the oil/water volume ratio was varied from 0 to 1, and the absorption from emulsions of sulfapyridine, salicylamide, and of acetanilide was investigated using in situ recirculation and loop techniques. In the absorption of drugs having partition coefficients of larger than one, amount of drugs in aqueous phase rather than their concentrations was a critical factor for the absorption from oil in water emulsions. In the absorption of poorly oil-soluble drugs, drug absorption from emulsions was larger than the one from aqueous solutions when the overall volume of emulsions was kept constant, which suggested the importance of absolute volume of aqueous phase in the absorption of drugs from such systems. Usually drugs dissolved in oil were absorbed mainly via aqueous phase.