OBJECTIVE  To optimize the formulation for sustained-release particles of matrine(MAT) and paeonol(PAE) and to primarily evaluate their quality.

METHODS The sustained-release particles were fabricated by the extrusion-spheronization method. Single factor analysis was conducted on the main sustained-release materials and their dosage, auxiliary sustained-release materials, and the total amount and proportion of mixed sustained-release materials, using the cumulative release rates of MAT and PAE in vitro as evaluation indicators. By combining central composition design-response surface methodology, the formulation of sustained-release materials was optimized, and the effects of the total amount and mass ratio of ethyl cellulose(EC) and chitosan(CS) on the cumulative release rate and release synchronization of MAT and PAE were investigated. The formulation characteristics, in vitro release, and preliminary stability tests of MAT-PAE-SRPs were evaluated, and the release process kinetic equation was fitted.

RESULTS The optimized formulation contained 23.5% EC and 17.1% CS as sustained-release materials. The yield, repose angle, bulk density and friability of final particles were 97.23%, 38.1°, 0.74 g·mL⁻¹ and 0.74%, respectively. The particles showed sustained release pattern in various media and released faster in acidic media with its release percentage >90% at 12 h. The release profile of MAT was fitted best with first order equation, and that of paeonol with Higuchi equation. The formation of SRPs improved the stability of both drugs.

CONCLUSION  The sustained-release effect of MAT-PAE-SRPs prepared by sustained-release materials EC and CS is significant, and the cumulative release rate and release synchronization of MAT and PAE are good, which can provide reference for the research of dual loaded sustained-release formulations.