Design and characterization of a submicronized o/w emulsion of diazepam for parenteral use

An innovative, injectable, submicronized emulsion delivery system into which diazepam was incorporated has been developed. This emulsion has been formulated to meet all the requirements for injection either i.v. or i.m. The technique utilized a high shear mixer followed by a two stage pressure homogenizer yielding a very fine monodispersed emulsion, the mean droplet size of which ranged from 100 to 150 nm. The combination of purified egg yolk phospholipid and non-ionic emulsifier, as a complex emulgator, together with a highly efficient emulsification technique yielded a fine diazepam emulsion with improved stability properties. An increase in the oil phase volume ratio caused a moderate but significant increase in the mean droplet size of the diazepam emulsion. A sharp and parallel elevation in mean droplet size and viscosity was observed in the emulsions containing 30% or more oily phase. The ζ-potential of the emulsified droplets was affected by the alteration of the pH, whereas no significant effect on mean droplet size was observed. The mean droplet size of diazepam emulsion decreased with increasing concentrations of the non-ionic emulsifier until reaching a minimum constant value. Mean droplet size of diazepam emulsion decreased, while ζ-potential increased with increasing phospholipid concentration. No changes in the various physicochemical properties were observed with increasing diazepam concentration.