Ability of Different Polymers to Inhibit the Crystallization of Amorphous Felodipine in the Presence of Moisture |
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Authors: | Hajime Konno Lynne S Taylor |
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Institution: | (1) Department of Industrial and Physical Pharmacy, School of Pharmacy, Purdue University, West Lafayette, IN 47907, USA;(2) Astellas Pharma Inc., 180 Ohzumi, Yaizu Shizuoka, 425-0072, Japan |
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Abstract: | Purpose To investigate the ability of various polymers to inhibit the crystallization of amorphous felodipine from amorphous molecular
dispersions in the presence of absorbed moisture.
Methods Spin coated films of felodipine with poly(vinylpyrrolidone) (PVP), hydroxypropylmethylcellulose acetate succinate (HPMCAS)
and hydroxypropylmethylcellulose (HPMC) were exposed to different storage relative humidities and nucleation rates were measured
using polarized light microscopy. Solid dispersions were further characterized using differential scanning calorimetry, infrared
spectroscopy and gravimetric measurement of water vapor sorption.
Results It was found that the polymer additive reduced nucleation rates whereas absorbed water enhanced the nucleation rate as anticipated.
When both polymer and water were present, nucleation rates were reduced relative to those of the pure amorphous drug stored
at the same relative humidity, despite the fact that the polymer containing systems absorbed more water. Differences between
the stabilizing abilities of the various polymers were observed and these were explained by the variations in the moisture
contents of the solid dispersions caused by the different hygroscopicities of the component polymers. No correlations could
be drawn between nucleation rates and the glass transition temperature (T
g) of the system. PVP containing solid dispersions appeared to undergo molecular level changes on exposure to moisture which
may be indicative of phase separation.
Conclusions In conclusion, it was found that for a given storage relative humidity, although the addition of a polymer increases the moisture
content of the system relative to that of the pure amorphous drug, the crystallization tendency was still reduced. |
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Keywords: | amorphous crystallization FTIR solid dispersion water sorption |
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