Design and optimization of self-nanoemulsifying drug delivery systems of simvastatin aiming dissolution enhancement

The aim of this work was to improve the in vitro dissolution of simvastatin through development of self-nanoemulsifying tablets. Various modified oils, surfactant and co-surfactant mixtures were used to prepare different self-nanoemulsifying drug delivery systems (SNEDDS) whose composition was optimized using drug-solubility, ternary phase diagram, system stability and droplet size distribution studies. Optimized SNEDDSs, with acceptable surfactant ratio, stability and particle size (nano-range) upon dilution with simulated gastric fluid (SGF, pH 1.2) under gentle agitation conditions, were loaded onto microcrystalline cellulose and nano-size colloidal silicon dioxide powders using loading factor (Lf) = 0.2 and excipient ratio (R) = 20. Prepared powders were compressed into tablets and the in vitroperformance of the prepared self-nanoemulsifying tablets was investigated. Results revealed that systems with 10% relatively polar oils (C8), 60% Cremophore® RH 40 (surfactant), and 30% Transcutol® HP (co-surfactant), acquired good self-nanoemulsification properties either in liquid or tableted forms. Prepared self-nanoemulsifying tablets demonstrated significantly higher dissolution rates, compared to direct compression tablets (DCT) and marketed tablet (Zocor®). In conclusion, self-nanoemulsifying tablets were able to introduce simvastatin successfully in a unique immediate-release solid dosage form.   Key words: Simvastatin, self-nanoemulsifying tablets, self-nanoemulsifying drug delivery systems (SNEDDS), droplet size.