Development and in-vitro characterization of sorbitan monolaurate and poloxamer 184 based niosomes for oral delivery of diacerein.

The aim of the study was to develop a niosomal drug delivery system for poorly soluble drugs with sorbitan monolaurate, poloxamer 184 and their mixture (sorbitan monolaurate and poloxamer 184) forming the niosomal surfactant system. Diacerein, a highly lipophilic antiosteoarthritic drug, was used as a model drug: it has variable oral bioavailability due to its poor aqueous solubility. The diacerein loaded niosomes were prepared with 1:1, 6:4 and 7:3 surfactant to cholesterol ratios at constant levels of dicetyl phosphate (2.5%) as a negative charge imparting agent. All studied ratios of surfactant to cholesterol produced diacerein loaded niosomes sized from 350 to 1000nm and with PDI values below 0.5. The transmission electron microscope images revealed well defined spherical vesicles. Mixed system formulations showed better entrapment efficiencies, with the best composition the entrapment efficiency being 90.5%, with smaller particle sizes and lower PDI values in comparison to formulations prepared with pure surfactant systems. With increasing cholesterol amount the niosomes were smaller, with more drug entrapped and better long term stability. Drug release studies showed improved dissolution profiles of all the niosomal formulations compared to pure diacerein.