Effects of drug concentration in inner aqueous phase and additives in oleaginous phase on release and bioavailability of isoniazid from multiple emulsion.

The effects of drug concentration in internal aqueous phase of stabilized w/o/w emulsion and additives in oleaginous phase on release characteristics of isoniazid were investigated. The release was significantly effected by both of the formulation variables. The release was enhanced initially with increasing concentration of drug in internal aqueous phase followed by a steady release at high concentration of isoniazid. The release declined substantially in the presence of aluminum tristearate, cetostearyl alcohol, and cholesterol, and it increased with egg lecithin and oleic acid in oily phase. The bioavailability was increased with a multiple-emulsion formulation.