Abstract
FT-Raman and FT-IR spectroscopy and Raman microscopy were employed to identify the structural characteristics of one amorphous and three crystalline phases of nifedipine, a common antihypertension drug of the 1,4-dihydropyridine family. A significant fraction of the nifedipine molecules in the glass are found to be frozen into metastable rotational conformations as a result of melt quenching. Moreover, the effect of relative humidity (RH = 20-80%) on the onset and rate of crystallization was studied at 40degreesC by means of in situ IR and Raman microscopy employing a controlled humidity cell. The nature and the relative abundance of the various crystallization products were analysed on the basis of the corresponding spectra of the neat compounds. Glassy nifedipine is found to crystallize to the thermodynamically stable a-polymorph via a transient metastable beta-nifedipine phase. Increasing RH in the range 20-60% is found to favour the surface crystallization of the glass to beta-nifedipine. At high RH (80%), beta-nifedipine is rapidly converted to alpha-nifedipine.
| Original language | English |
|---|---|
| Pages (from-to) | 353-359 |
| Number of pages | 7 |
| Journal | JOURNAL OF RAMAN SPECTROSCOPY |
| Volume | 35 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - May 2004 |
Keywords
- nifedipine
- drugs
- polymorphism
- crystallization
- Raman microscopy
- FT-IR
- infrared microscopy
- moisture
- CALCIUM-CHANNEL ANTAGONISTS
- FOURIER-TRANSFORM RAMAN
- CRYSTAL-STRUCTURES
- SOLID-STATE
- SPECTROSCOPY
- CRYSTALLIZATION
- TRANSITION
- FORMS
- GLASS