Raloxifene is an oral selective estrogen receptor modulator drug. It has estrogenic actions on bone and anti-estrogenic actions on the uterus and breast. It is used to prevent osteoporosis in postmenopausal women and to reduce the risk of invasive breast cancer. The absolute bioavailability of the drug is only 2% because of extensive hepatic first-pass metabolism. Raloxifene has low absorbance because of its lipophilic nature and poor aqueous solubility. Use of microemulsion formulation as a novel drug delivery system leads to increase aqueous solubility and bioavailability of this drug. The main objective of the present study is to formulate and evaluate a microemulsion system of raloxifene. This system includes sesame oil, tween80, glycerin and water as an appropriate oil phase, surfactant, co-surfactant and aqueous phase, respectively. The microemulsion area was identified by constructing pseudo-ternary phase diagrams. Three various surfactant to co-surfactant ratios were investigated e.g. 2:1, 4:1 and 5:1. Synthesized microemulsion samples were evaluated according to the droplet size, zeta potential, polydispersity index, conductivity, refractive index, pH and stability. All samples had the appropriate particle size in nano metric rang, The best sample with highest stability and clearance was selected based on analysis results. Raloxifene drug was loaded to this formulation with 1% w/w. Results showed that the mean droplet size and zeta potential of this raloxifene microemulsion sample were 31.25nm and 11.3mV, respectively. The polydispersity index was lower than 0.5. The conductivity, pH and refractive index were 752µs, 5.52 and 1.4025, respectively. Particle size variation and phase separation were not observed during 3 months after sample synthesis. Furthermore, the centrifuge test showed good physical stability. In conclusion, this new form of raloxifene drug is suggested as an effective drug delivery system for oral therapy.

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