Effect of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone).
OBJECTIVE
The aim was to investigate the influence of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations, as indicators of stability, of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone) (PVP).


METHODS
Amorphous lactose and composite particles of amorphous lactose with different contents and molecular weights of PVP were prepared by spray drying. The nanostructure of the particles was analyzed by x-ray powder diffractometry, the morphology by light microscopy and SEM, the glass transition temperatures (Tg), crystallization temperatures (Tc), heats of crystallization and melting temperatures by differential scanning calorimetry, and moisture-induced crystallizations gravimetrically and by microcalorimetry.


RESULTS
All the types of particles prepared were amorphous. The Tg was unchanged or only marginally increased as a result of the inclusion of PVP. However, crystallization temperature, time to moisture-induced crystallization, and particle morphology were affected by both content and molecular weight of PVP.


CONCLUSIONS
Increased content and molecular weight of PVP may have the potential to increase the physical stability of amorphous lactose. However, Tg seems not to be a relevant indicator for the stability of this type of amorphous composite materials.
Berggren
Jonas
J
Department of Pharmacy, Uppsala University, Box 580, SE-751 23 Uppsala, Sweden.
Alderborn
Göran
G
D004355:Drug Stability; D005612:Freeze Drying / Q000379:methods; D006358:Hot Temperature; D006813:Humidity; D007785:Lactose / Q000737:chemistry*; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry*
D011108:Polymers; D011205:Povidone; D007785:Lactose