Influence of processing conditions in the manufacture of O/W creams - II. Effect on drug availability

O/W creams prepared in three mechanical conditions (F with a hand blender; S turbomixer; T vacuum turbo-emulsor) produced different dispersion grades of the internal phase and different rheological characteristics by using surfactants of different chemical nature (polyoxyethylene-cetostearyl alcohols and polyglyceryl-3-methylglucose distearate). Three tests were used (an in vitro release test across a porous membrane; an in vitro simulated absorption test across a porous membrane impregnated with isopropyl myristate; an in vivo absorption test based on the intensity and duration of the erythema produced by methyl nicotinate after application of the cream on the skin) to assess whether the different physical characteristics influence drug availability from the creams. The different physical characteristics due to the mechanical conditions of emulsifying and gelification appeared not to influence drug release and in vivo absorption.