Hydroxypropylmethylcellulose (HPMC) as emulsifier for submicron emulsions: influence of molecular weight and substitution type on the droplet size after high-pressure homogenization.

Hydroxypropylmethylcellulose (HPMC) is a known emulsifier as well as a common viscosity enhancer in eye drops. Therefore, HPMC stabilized emulsions appear as interesting drug carriers for ophthalmic use and as a suitable treatment of dry eye syndrome. Since submicron emulsions are known to have an improved drug delivery, attempts were made to reduce the emulsion's droplet size by high-pressure homogenization. Droplet size was dependent on the homogenization pressure and the polymer content. Differences were found between emulsions stabilized with higher and lower molecular weight HPMC. Smaller droplet sizes were obtained with the shorter chained HPMC. No considerable influence of the substitution type was observed.