Effects of the physicochemical properties of the emulsion formulation on the bioavailability of ethyl 2-chloro-3-[4-(2-methyl-2-phenylpropyloxy)phenyl]propionate in rats

The effect of the physicochemical properties of the emulsion formulation on the absorption of ethyl 2-chloro-3-4-(2-methyl-2-phenylpropyloxy)phenyl]propionate (AL-294) in rats and dogs was studied. When emulsions of different particle sizes were administered to rats, the higher the ratio of Tween-80 to the drug was, the smaller was the particle size and the higher was the absorption. When the emulsions of similar particle size (2 microns) with different Tween-80 ratios were administered to rats, no significant difference was observed in the extent of absorption. The absorption of AL-294 was correlated with the dissolution rate from the oil phase to the aqueous phase but not correlated with the amount of AL-294 solubilized by Tween-80. These results indicate that the absorption of AL-294 from emulsions depends mainly on the particle size in the gastro-intestinal fluid and that Tween-80 serves only to reduce the particle size in the emulsion.