Formulation and physicochemical characterisation of a novel self-microemulsifying delivery system as hydrotropic and solubilising agent for penfluridol

As a poorly water-soluble chemical, penfluridol is used as a maintenance drug for individuals with chronic schizophrenia. A novel self-microemulsifying drug delivery system has been successfully developed to benefit the solubility of penfluridol. Pseudo-ternary phase diagrams were constructed to investigate the phase behaviour and to assess the effects of different co-surfactants and the mass ratios of surfactant to co-surfactant (Km) on the phase regions. Optimal compositions of the formed systems were screened via viscosity studies and microemulsion droplet size tests. The optimal formulation of penfluridol-loaded self-microemulsion consists of penfluridol 5.0%, oil (MCT) 15.8%, surfactant (cremophor EL) 52.8%, co-surfactant (PEG-400) 26.4%, with the average particle size at approximately (53.5±4.3) nm. Transmission electron microscopy (TEM) revealed the spherical nature and size homogeneity of the microemulsion droplets. No significant variations (droplet sizes and penfluridol contents) in microemulsion were observed over a period of 30 days at 4°C and 25°C, respectively. The developed self-microemulsion proved to be a potential candidate to enhance the solubility of penfluridol.