Thermal analysis and dissolution characteristics of nifedipine solid dispersions

Solid dispersions of nifedipine prepared with two hydrophilic carrier systems, Gelucire (44/14)/PEG 600 and PVP (K12-K25)/PEG 6000 by fusion or fusion/solvent method were characterized by thermal analysis for comparisons. Results demonstrated that both carrier systems were able to prohibit the crystallization of nifedipine after the mixture melted at a higher temperature at a ratio exceeding 50%. The extent of forming amorphous nifedipine due to the inhibition of crystallization, also raised with the increasing ratio of the carrier. When mixing with PEG 6000 at a ratio of 3:1, the melting temperature of nifedipine dropped to 110°C. Dissolution tests further demonstrated that nifedipine, once fused with these carriers, possessed an enhanced dissolution rate. As to the Gelucire (44/14)/PEG 600 system, the dissolution rates from those samples prepared at a higher temperature were faster than those prepared at the melting point of Gelucire. The dissolution rate increased with the amount of Gelucire added in the preparation. For the PVP/PEG 6000 carrier system, the dissolution rate of nifedipine increased with the amounts of both PVP and PEG 6000. However, a slower dissolution rate was also noted resulted from higher molecular weight of PVP.