Formulation and biopharmaceutical evaluation of supersaturatable self-nanoemulsifying drug delivery systems containing silymarin

The first objective of this study was to optimize a supersaturatable self-nanoemulsifying drug delivery system (SSNEDDS) containing silymarin through the investigation of the single and synergistic effect of either SNEDDS or a precipitation inhibitor on dissolution efficiency (DE) of silymarin. The bioavailability and hepatoprotective activity of S-SNEDDS were then compared to those of a branded product (Legalon (R), Meda). SNEDDS containing silymarin was developed by titration technique, and Poloxamer 407 was selected as the optimal precipitation inhibitor by using casting film and solvent-shift method. The interaction of silybin (the major active constituent of silymarin) and the polymer was then determined by differential scanning calorimetry, powder X-ray diffractometry (PXRD), Fourier transforms infrared spectroscopy and H-1 NMR analysis. The combination of two techniques including SNEDDS and addition of 10% of Poloxamer 407 remarkably increased DE4h (88.28%) compared to the reference product (6.41%). The relative bioavailability of S-SNEDDS versus Legalon (R) was about 760%. The hepatoprotective activity of S-SNEDDS in CCl4-induced mice was also superior to the commercial product in declining both the levels of serum transaminases (ALT, AST) and lipid peroxidation as well as glutathione and superoxide dismutase (SOD) activities under tested doses calculated as silybin (10, 25 and 50 mg/kg). These biopharmaceutical and pharmacological advantages of S-SNEDDS indicated prospects in the development of a novel product that offers lower strength of silymarin while enhancing therapeutic outcomes.