Influence of Oil Phase Surface Properties on the Physicochemical Characteristics of Meloxicam Self-microemulsifying Drug Delivery Systems

Introduction Preparation of self-microemulsifying drug delivery systems (SMEDDS) is a promising delivery approach for drugs with poor aqueous solubility to enhance their dissolution properties and hence oral bioavailability. The objective of the present study was to define the influence of the oily phase surface properties of meloxicam self-microemulsifying drug delivery systems on the physicochemical properties of the formulation. Methods Minitab software was applied for the definition of a response surface experimental design. The shake flask method was used to determine the solubility of Meloxicam in formulation ingredients and prepared formulations. Refractive index, transmittance percentage, particle size and zeta potential, and dissolution behaviour of each formulation were determined. Results Meloxicam reveals higher solubility in Capryol PGMC (1.347 mg/ml) and PEG 400 (28.63 mg/ml) respectively. Surface tensions of pure Miglyol 812, Capryol PGMC, Labrasol, PEG 400, PG, and Transcutal P were 36.8, 36, 40.44, 40.22, 41, and 37.34 dyne/cm, and the interfacial tensions of Capryol PGMC and Miglyol 812 against the water were 7 and 12 dyne/cm respectively. In the majority of formulations, the solubility of meloxicam was higher in Capryol-containing formulations compared to Miglyol-containing ones. The lower surface tension of formulations associated with higher solubility of meloxicam, better dissolution, and lower emulsification times. Capryol-Labrasol-PEG 400 containing formulations show higher transmitted percentages. The size of droplets has been increased with an increase in the surface tension of formulations. Conclusion Lower surface tensions of SMEDDS excipients, especially oil phases, are associated with better physicochemical characteristics, i.e. higher solubilizing potential, emulsification ability, droplet size, transparency, refractive index, and dissolution behaviour.