Encapsulation of hydrophobic drugs in a copolymer: Glass transition behavior and miscibility evaluation |
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| Authors: | R. Jayachandra Babu Witold Brostow Oladiran Fasina Ioannis M. Kalogeras Sateeshkumar Sathigari Aglaia Vassilikou‐Dova |
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| Affiliation: | 1. Department of Pharmacal Sciences, Harrison School of Pharmacy, Auburn University, Auburn, Alabama 36849;2. Laboratory of Advanced Polymers and Optimized Materials (LAPOM), Department of Materials Science and Engineering, and Center for Advanced Research and Technology (CART), University of North Texas, Denton, Texas 76203‐5017;3. Department of Physics, University of North Texas, Denton, Texas 76203‐5017;4. Department of Biosystems Engineering, Auburn University, Alabama 36849;5. Solid State Physics Section, Department of Physics, University of Athens, Panepistimiopolis, Zografos 157 84, Greece |
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| Abstract: | The knowledge of glass transition temperatures Tg in drug + polymer systems is indispensable for drug encapsulation. Tg values as a function of composition make possible the determination whether a given polymer is miscible or compatible with the drug and whether the polymer will provide release of the drug into organism within an acceptable rate range. We have used differential scanning calorimetry and Fourier‐transform infrared spectroscopy to evaluate miscibility in solid dispersions of the drugs carvedilol, itraconazole, nevirapine, and nimodipine in the pharmaceutical grade copolymer poly(vinyl pyrrolidone‐co‐vinyl acetate) (PLS‐630 Copovidone). Successful drug encapsulation is discussed in terms of thermophysical behavior (suppression of crystallization, negative excess volumes of mixing) and intermolecular interactions (concentrations of proton donating/accepting groups) in drug + polymer systems. Several equations were applied to the complex s‐shaped Tg(?) patterns obtained (? being the mass fraction of the drug). The best agreement of calculations with experiment is achieved using a recently proposed three‐parameter equation, symmetric with respect to the equal concentration of both components. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers |
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