| Theoretical and practical approaches for prediction of drug-polymer miscibility and solubility. | |
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MedLine Citation:
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PMID: 16933098 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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PURPOSE: Crystallization of drugs formulated in the amorphous form may lead to reduced apparent solubility, decreased rate of dissolution and bioavailability and compromise the physical integrity of the solid dosage form. The purpose of this work was to develop thermodynamic approaches, both practical and theoretical, that will yield a better understanding of which factors are most important for determining the ability of polymers to stabilize amorphous active pharmaceutical ingredients (API). MATERIALS AND METHODS: Lattice based solution models were used to examine miscibility criteria in API-polymer blends. Different methods were used to estimate the Flory-Huggins interaction parameter for model API-polymer systems consisting of felodipine or nifedipine with poly(vinylpyrrolidone) (PVP). These were melting point depression and determination of solubility parameters using group contribution theory. The temperature and enthalpy of fusion of crystalline API alone and the fusion temperature of the API in the presence of the polymer were measured by differential scanning calorimetry. The resultant thermal data were used to estimate the reduced driving force for crystallization and the solubility of the API in the polymer. RESULTS: Flory-Huggins theory predicts that, for typical API-polymer systems, the entropy of mixing is always favorable and should be relatively constant. Due to the favorable entropy of mixing, miscibility can still be achieved in systems with a certain extent of unfavorable enthalpic interactions. For the model systems, interaction parameters derived from melting point depression were negative indicating that mixing was exothermic. Using these interaction parameters and Flory-Huggins theory, miscibility was predicted for all compositions, in agreement with experimental data. A model was developed to estimate the solubility of the API in the polymer. The estimated solubility of the model APIs in PVP is low suggesting that kinetic rather than thermodynamic stabilization plays a significant role in inhibiting crystallization. CONCLUSIONS: The thermodynamics of API-polymer systems can be modeled using solution based theories. Such models can contribute towards providing an understanding of the compatibility between API and polymer and the mechanisms of physical stabilization in such systems. |
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Authors:
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Patrick J Marsac; Sheri L Shamblin; Lynne S Taylor |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2006-08-24 |
Journal Detail:
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Title: Pharmaceutical research Volume: 23 ISSN: 0724-8741 ISO Abbreviation: Pharm. Res. Publication Date: 2006 Oct |
Date Detail:
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Created Date: 2006-10-05 Completed Date: 2006-12-14 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 8406521 Medline TA: Pharm Res Country: United States |
Other Details:
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Languages: eng Pagination: 2417-26 Citation Subset: IM |
Affiliation:
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Department of Industrial and Physical Pharmacy, School of Pharmacy, Purdue University, West Lafayette, Indiana 47907, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Algorithms Calcium Channel Blockers / chemistry Chemistry, Physical Entropy Felodipine / chemistry Forecasting Models, Chemical Nifedipine / chemistry Pharmaceutic Aids / chemistry Pharmaceutical Preparations / chemistry* Physicochemical Phenomena Polymers / chemistry* Povidone / chemistry Solubility Thermodynamics |
| Chemical | |
Reg. No./Substance:
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0/Calcium Channel Blockers; 0/Pharmaceutic Aids; 0/Pharmaceutical Preparations; 0/Polymers; 21829-25-4/Nifedipine; 72509-76-3/Felodipine; 9003-39-8/Povidone |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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