Spectroscopic identification of an amorphous-to-crystalline drug transition in a solid dispersion SCH 48461 capsule formulation

Amiodarone hydrochloride: enhancement of solubility and dissolution rate by solid dispersion technique

abstract Amiodarone HCl is an antiarrhythmic agent, which has low aqueous solubility and presents absorption problems. This study aimed to develop inclusion complexes containing hydrophilic carriers PEG 1500, 4000 and 6000 by fusion and kneading methods in order to evaluate the increase in solubility and dissolution rate of amiodarone HCl. The solid dispersion and physical mixtures were characterized by X-ray diffraction, FT-IR spectra, water solubility and dissolution profiles. Both methods and carriers increased the solubility of drug, however PEG 6000 enhanced the drug solubility in solid dispersion better than other carriers. Different media were evaluated for the solubility study, including distilled water, acid buffer pH 1.2, acetate buffer pH 4.5 and phosphate buffer pH 6.8 at 37 ºC. Based on the evaluation of the results obtained in the study phase solubility carriers PEG 4000 and PEG 6000 were selected for the preparation of the physical mixture and solid dispersion. All formulations were prepared at drug-carrier ratios of 1:1 to 1:10(w/w). The results of in vitro release studies indicated that the solid dispersion technique by fusion method in proportion of 1:10 (w/w) increased significantly the dissolution rate of the drug. X-ray diffraction studies showed reduced drug crystallinity in the solid dispersions. FT-IR demonstrated interactions between the drug and polymers.

Evaluation of solid state form of troglitazone by solid state NMR spectroscopy

The solid state forms of troglitazone drug substance and diastereomers were characterized using solid state nuclear magnetic resonance (SSNMR) spectroscopic method. The SSNMR spectroscopy could distinguish the hydrated and the non-hydrated RR/SS forms more clearly than powder X-ray diffractometry (PXRD). The SSNMR result supported that troglitazone drug substance consists of diastereomers as a simple physical mixture. SSNMR spectroscopy was also able to characterize the solid state forms of troglitazone in tablets while PXRD was unable to because of interference from the pharmaceutical additives. Troglitazone was proved to exist in amorphous form in tablets, and keep its solid state form amorphous against heat and humidity. SSNMR spectroscopy thus provides very important information for the development of the pharmaceutical formulation of troglitazone.

Prediction of apparent equilibrium solubility of indomethacin compounded with silica by 13C solid state NMR

The apparent equilibrium solubility (AES) of indomethacin increased by co-grinding with silica. Change in the long- and short range disorder of indomethacin by co-grinding was examined by X-ray powder diffraction and 13C solid state NMR, respectively, to elucidate the increased AES. Since the increase in AES was particularly marked after complete disappearance of X-ray diffraction peaks, we attributed the enhanced AES primarily to the short range disorder on the molecular basis. This was confirmed by a high correlation between the standardized full width at half maximum (SFWHM) of the specific peaks observed by 13C solid state NMR and log (AES). The correlation enables the prediction of AES as well.

New perspectives for the on-line monitoring of pharmaceutical crystallization processes using in situ infrared spectroscopy

Chemists and engineers involved in the industrial production of solid drugs have to deal with difficult new challenges, including the on-line mastery of the crystal habits and size distribution, the control of polymorphic transitions or the improvement of the chemical purity. A major limitation to improving the control of industrial crystallizers lies in the lack of versatile, accurate and reliable on-line sensors. It is shown that supersaturation measurements can be performed using in situ ATR mid-infrared spectroscopy thus providing valuable real-time information about the crystallization process. Several case studies are presented to illustrate new potential applications of the technique. The reported experimental results outline recent advances in the acquisition of key data characterizing the solute/solvent system in question (i.e. solubility, metastability, phase transformations...), the design of on-line control strategies capable of improving both the crystal size distribution (CSD) and the reproducibility of the quality of the final product, the assessment of improved operating strategies (e.g. seeding batch crystallizers), and the monitoring of polymorphic transitions during cooling crystallization operations. The possibility of evaluating on-line the process impurities, which could allow the reduction of batch-to-batch variations of the quality of the solid product, is also briefly envisaged.

19F solid-state NMR spectroscopic investigation of crystalline and amorphous forms of a selective muscarinic M3 receptor antagonist, in both bulk and pharmaceutical dosage form samples

The purpose of the following investigation was to display the utility of 19F solid-state nuclear magnetic resonance (NMR) in both distinguishing between solid forms of a selective muscarinic M3 receptor antagonist and characterizing the active pharmaceutical ingredient in low-dose tablets. Ambient- and elevated-temperature solid-state 19F fast (15 kHz) magic-angle spinning (MAS) NMR experiments were employed to obtain desired spectral resolution in this system. Ambient sample temperature combined with rotor frequencies of 15 kHz provided adequate 19F peak resolution to successfully distinguish crystalline and amorphous forms in this system. Additionally, elevated-temperature 19F MAS NMR further characterized solid forms through 19F resonance narrowing brought about by the phenomenon of solvent escape. Similar solvent dynamics at elevated temperatures were utilized in combination with ambient-temperature 19F MAS NMR analysis to provide excipient-free spectra to unambiguously identify the active pharmaceutical ingredient (API) conversion from crystalline Form I to the amorphous form in low-dose tablets. It is shown that 19F solid-state NMR is exceptionally powerful in distinguishing amorphous and crystalline forms in both bulk and formulation samples.

Determination of indomethacin crystallinity in the presence of excipients using diffuse reflectance near-infrared spectroscopy

Studies were conducted to investigate the use of near-infrared spectroscopy for determining the crystallinity of indomethacin in multi-component physical mixtures. Three calibration sets of amorphous/crystalline indomethacin physical mixtures were prepared over the composition range of 0-100% crystallinity. Each of the three calibration sets was diluted step-wise with increasing amounts of a single excipient (Avicel, alpha-lactose monohydrate, or sodium chloride). Near-infrared spectra were obtained after each round of dilutions using diffuse reflectance sampling on samples contained in glass vials. After a second derivative transformation, standard curves were constructed by plotting percent indomethacin crystallinity against the ratio of responses at two wavelengths. At dilution levels up to 75% Avicel or lactose, the calibration models demonstrated high coefficients of determination and low standard errors. Dilution with sodium chloride did not produce comparable results and it was necessary to use partial least-squares regression to achieve a similar level of error. These findings were confirmed with separate validation sets. An investigation of instrument error showed that the impact of instrument variability on quantification generally increased as a function of the dilution level.

Stability of amorphous indomethacin compounded with silica

The stability of indomethacin (IM) compounded with SiO(2) either by co-grinding or by melt-quenching was examined by recrystallization kinetics under the conditions 30 degrees C and 11% relative humidity. A decrease of the recrystallization rate with and without an appreciable induction period was observed in both compounds. Higher stability of amorphous IM compounded with SiO(2) was attained by prolonged co-grinding than by melt-quenching. This was explained by the stronger chemical interaction at the interface between IM and SiO(2) by co-grinding, as revealed by (29)Si and (13)C solid state NMR. Incomplete co-grinding with the rest of the crystalline state, however, made the amorphous state appreciably unstable, since the remaining crystallites serve as seeds for recrystallization.