Preparation and Characterization of Silymarin Synchronized and Sustained Release Dropping Pill

Purpose: This study aimed to develop a synchronized and sustained-release silymarin dropping pill, and to evaluate its pharmacokinetic characteristics. Method: Polyoxyethylene stearate, glyceryl monostearate, and stearic acid were used to prepare the dropping pills. X-ray powder diffraction, differential scanning calorimetry, and release were used to evaluate its physicochemical properties. The plasma concentration of silybin in beagle dogs after oral administration of silymarin dropping pills and silymarin capsule was determined by RP-HPLC. Results: Synchronized release was achieved with high similarity factor f2 values between every set of two of the five components. Mean plasma concentration-time curves of silymarin after oral administration of dropping pills in beagle dogs were in accordance with first-order absorption and open twocompartment model. The Tmax, Cmax, and AUC0-∞ of dropping pills in beagle dogs were 0.8750±0.13 h, 0.8183±0.07 μgml-1, and 2.274±0.90 μghml-1, respectively. Silymarin dropping pills prolonged in vivo exposure and reduced maximum in vivo concentration, achieving a stable level in the serum. Conclusion: The combination of solid dispersion technique and dropping pill formulation allowed synchronized release of multiple components in herbal medicine, and has potential application in the development of sustained release in herbal medicine.