Nolan, Christine M Gelbaum, Leslie T Lyon, L Andrew Copyright (c) 2005 John Wiley & Sons, Ltd.ġ H NMR investigation of thermally triggered insulin release from poly(N-isopropylacrylamide) microgels. The results were supported by DSC, powder XRD, FTIR and solution-state NMR measurements. The effect of crushing the amorphous samples has been studied by 13C NMR nifedipine recrystallises but indomethacin does not. It is shown that, under the conditions of the experiments, recrystallisation of nifedipine can be detected already at 70 degrees C, whereas this does not occur until 110 degrees C for indomethacin. Recrystallisation of the two drugs has been followed by proton bandshape measurements at higher temperatures. Comparison of relaxation time data for the crystalline and amorphous forms of each compound reveals a greater difference for nifedipine than for indomethacin, which again probably relates to real-time stabilities. There is a change in slope for T 1 H and T 1rho H at the glass transition temperature (Tg) for indomethacin, but this occurs a few degrees below Tg for nifedipine, which is perhaps relevant to the lower real-time stability of the amorphous form for the latter compound. Since the two drug compounds are potential candidates for formulation in the amorphous state, we have examined quench-cooled melts in detail by variable-temperature 13C and 1 H NMR. The relevant motion is probably an internal rotation and it is suggested that this involves the C-OCH3 group. The associated activation energy is 38 kJ mol(- 1). Variable-temperature 1 H relaxation measurements of static samples have revealed a T 1rho minimum for indomethacin at 17.8 degrees C. The signal for the C-Cl carbon of indomethacin has been studied as a function of applied magnetic field, and the observed bandshapes have been simulated. We have characterised the stable polymorphic forms of two drug molecules, indomethacin ( 1) and nifedipine (2) by 13C CPMAS NMR and the resonances have been assigned. Characterisation of indomethacin and nifedipine using variable-temperature solid-state NMR.Īpperley, David C Forster, Angus H Fournier, Romain Harris, Robin K Hodgkinson, Paul Lancaster, Robert W Rades, Thomas
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