Sudden rise of crystal growth rate of nifedipine near Tg without and with polyvinylpyrrolidone

The crystal growth of nifedipine in the # polymorph has been measured from T-g + 50 to T-g - 20 K, where T-g = 315 K is the glass transition temperature. A sudden 10-fold rise of growth rate was observed as the temperature decreased from above to below Tg accompanied by a change of growth morphology. This is the same phenomenon reported by Oguni and coworkers [Hikima T, Adachi Y, Hanaya M, Oguni M. 1995. Phys Rev B 52:3900-39081 for other compounds of lower Tg. The phenomenon persisted in the presence of 1% polyvinylpyrrolidone (PVP). The presence of 1% or 2% PVP had little effect on the growth rate near Tg + 50 K, but reduced the growth rate by 100-fold at T-g + 9 K. These kinetic features are relevant to predicting the stability of amorphous drugs. 0 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:1131-1138, 2007.