Influence of various drugs on the glass transition temperature of poly(vinylpyrrolidone): a thermodynamic and spectroscopic investigation

Purpose: To determine the influence of hydrogen bonding and solubility para meter on the glass transition temperature (To of various drug-poly(vinylpyr rolidone) blends. Methods: The T-g of PVP films containing either acetamino phen, naproxen, salicylamide, carbamazepine, griseofulvin or propranolol hy drochloride were measured using differential scanning calorimetry. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction was used to ch aracterize the specific interactions between the drug-PVP blends and the ph ysical state of the films, respectively. The total solubility parameter and its individual components were calculated using the method of Van Krevelen . Results: Salicylamide displayed the greatest plasticizing effect, depress ing the T-g to the minimum. This was consistent with the FTIR data, which i ndicated the presence of hydrogen bonding with PVP. Griseofulvin showed the least plasticizing effect due to lack of interaction with PVP. All the dru gs except griseofulvin were amorphous within the film up to 30% (w/w) drug composition. The correlation between the various components of the solubili ty parameters and the plasticizing effect of drugs was very poor. Conclusio ns: Spectroscopic investigation for the presence of interaction between the drugs and PVP proved to be extremely predictive of the plasticizing effect of various drugs. In contrast, solubility parameters appeared to be far le ss sensitive indicators of drug-PVP miscibility. (C) 2001 Elsevier Science B.V. All rights reserved.