title: FTIR spectroscopic study of poly(ethylene glycol)-nifedipine dispersion stability in different relative humidities.
abstract: Solid dispersion has shown to be a promising formulation strategy to enhance dissolution for hydrophobic drugs. However, solid dispersions are often thermodynamically unstable, there is a continuous interest in studying their stabilities. In this study, attenuated total reflectance Fourier transform infrared (ATR-FTIR) was used to compare the amount of crystalline nifedipine formed in different formula of poly(ethylene glycol) (PEG)-nifedipine solid dispersions when exposed at various relative humidities (RHs) for 2 h at 40°C. The ratio of the crystalline nifedipine band and an internal reference band in the out of plane δ(C-H) region has been used to indicate the relative degree of drug crystallisation in a sample. A band ratio of ∼0.05 and 0.5 was respectively indicative of a fully amorphous or crystallised drug in the formula. Results show that increasing the RH generally increases the amount of crystalline nifedipine. Formulations with low (5%, w/w) nifedipine concentration in higher molecular weight PEG were found to be better at resisting crystallisation. Deliquescence of the 10% nifedipine in PEG 4000 was observed at 77% and 100% RH with a reduction in crystalline nifedipine. All 5% (w/w) nifedipine samples were stable at RH below 77%. Crystallisation of nifedipine occurred at all RH when drug loading was increased to 10% (w/w).
authors.affiliation: Institute of Pharmaceutical Science, King's College London, London, SE1 9NH, UK.
authors.forename: Waleed S
authors.initials: WS
authors.lastname: Iqbal
authors.forename: K L
authors.initials: KL
authors.lastname: Chan
mesh_terms: D003460:Crystallization; D004339:Drug Compounding; D004355:Drug Stability; D005079:Excipients / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008968:Molecular Conformation; D008970:Molecular Weight; D009543:Nifedipine / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013501:Surface-Active Agents / Q000737:chemistry*; D013535:Suspensions; D014665:Vasodilator Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D005079:Excipients; D013501:Surface-Active Agents; D013535:Suspensions; D014665:Vasodilator Agents; D014867:Water; D011092:Polyethylene Glycols; D009543:Nifedipine
keywords: FT-IR; bioavailability; drug loading; humidity; infrared spectroscopy; molecular dispersion; polymer; polymorphism; quantitative analysis; univariate analysis