Investigating Miscibility and Molecular Mobility of Nifedipine-PVP Amorphous Solid Dispersions Using Solid-State NMR Spectroscopy

Solid-state NMR (SSNMR) H-1 T-1 and T-1p relaxation times were used to evaluate the miscibility of amorphous solid dispersions of nifedipine (NIF) and polyvinylpyrrolidone (PVP) prepared by three different methods: melt quenching in the typical lab setting, spray drying and melt quenching in the NMR rotor while spinning. Of the five compositions prepared by melt quenching in the lab setting, the 95:5 and 90:10 NIF:PVP (w:w) amorphous solid dispersions were not miscible while 75:25, 60:40, and 50:50 NIF:PVP dispersions were miscible by the H-1 T-1p measurements. domain size of the miscible systems was estimated to be less 4.5 nm. Amorphous solid dispersions with composition of 90:10 NIF:PVP prepared by spray drying and melt.. quenching in the NMR rotor showed miscibility by H-1 T-1p values. Variable-temperature SSNMR H-1 T-1p relaxation measurements revealed a change in relaxation time at approximately 20 degrees C below T-g, suggesting increased molecular mobility above that temperature.