Alginate as a potential diphase solid dispersion carrier with enhanced drug dissolution and improved storage stability

The objective of this study was to explore the feasibility of using alginate as a promising diphase solid dispersion carrier to enhance dissolution rate of BCS II drugs with improved stability. Taking lovastatin and indomethacin as model drugs, solvent evaporation method was used to prepare solid dispersions. The drug/polymer compatibility was predicted by Hansen solubility parameter and the drug/polymer ratio was screened based on dissolution study, drug existing state in solid dispersion was characterized by DSC and XRPD. Accelerated stability of the solid dispersion was assessed and compared with that of HPMCAS based system. Phase behavior of the solid dispersion before and after stability study was characterized using polar microscope and Raman mapping. It was found that the optimal drug/alginate ratio was drug dependent and drug existing state was related to drug/alginate miscibility. Stability studies revealed that alginate improved the stability of solid dispersions regardless of drug existing state and a better stability was obtained compared to HPMCAS based system. Raman mapping and SEM study revealed that micro phase separation of solid dispersion was the main reason for the slight decrease in drug dissolution after accelerating experiment. In conclusion, alginate can be used as a promising diphase solid dispersion carrier with significantly improved dissolution rate and storage stability.