Detection of Low Levels of Amorphous Lactose using H/D Exchange and FT-Raman Spectroscopy

Purpose  To demonstrate the potential of monitoring H/D exchange by FT-Raman spectroscopy as a tool for the detection and quantification of low levels of amorphous lactose in formulations. Methods  Samples containing different proportions of amorphous and crystalline lactose were prepared. H/D exchange was carried out by exposing the samples to a flow of D₂O vapour. A calibration curve was constructed from the FT-Raman spectra of the deuterated samples by integrating the ν(OD) band and normalizing to an internal standard. This method was benchmarked against a conventional approach using Raman spectroscopy where the ratio of Raman bands associated with crystalline and amorphous lactose is used to estimate the amorphous content. Results  The H/D exchange method revealed a linear response over the entire composite range with an excellent correlation coefficient (R ² = 0.999). The sensitivity of this approach in detecting the amount of amorphous lactose present in a blend is significantly greater than that offered by conventional FT-Raman in the 0–10% level of amorphous material. Conclusions  A non-destructive method that is capable of providing reproducible measurements of low levels of amorphous material in lactose has been demonstrated and this method has enhanced sensitivity relative to approaches using Raman spectroscopy without deuteration.     

Quantitative Determination of the Extent of Neutralization of Carboxylic Acid Functionality in Carbopol® 974P NF by Diffuse Reflectance Fourier Transform Infrared Spectrometry Using Kubelka-Munk Function

Purpose. The purpose of this study was to develop an analytical method for the quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol^® 974P NF using Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFT) with Kubelka-Munk function analysis. Methods. Carbopol^® 974P NF is a high molecular weight, chemically crosslinked polymer of acrylic acid, that has the C=O stretching band of the unionized carboxylic acid function at 1695 cm^–1. The quantitative determination of the extent of neutralization of the carboxylic acid function in Carbopol^® 974P NF is based upon the asymmetrical C =O stretching of the carboxylate anion at 1570 cm^–1 measured by DRIFT Spectroscopy. Results. To overcome spectral differences arising from sample preparation (powders, granules and tablets) and in an effort to increase the precision of the analytical method, the following approaches were used: (1) an internal standard, (2) first derivative of the spectrum to eliminate the effect of baseline drift and (3) the ratio of the first derivative of the C=O stretch of the carboxylate anion peak (1570 cm^–1) in the neutralized Carbopol^® 974P NF to that of the peak of the internal standard (866 cm^–1). The above data treatment techniques proved to be superior to the usual methods of peak height or peak area. The calibration curve of the ratio of the first derivative (1570 cm^–1/866 cm^–1) was a linear function of the mass of sodium carboxylate over the range from 0.0% to 100.0% neutralization of the carboxylic acid function in Carbopol^® 974P NF (Fig. la). No particle size or sample preparation effects were noted within the experimental error. Conclusions. DRIFT Spectroscopy using the Kubelka-Munk function is a powerful tool for the routine determination of the extent of neutralization of the carboxylic acid function in Carbopol^® 974P NF in complex pharmaceutical formulations.     

Using the low-frequency Raman spectroscopy to analyze the crystallization of amorphous indomethacin

This paper gives a detailed analysis of the low-frequency Raman spectrum (LFRS) in the 5–250 cm⁻¹ region, corresponding to collective vibrations, in the crystalline forms and in the amorphous state of indomethacin (IMC). This study points out the high sensitivity of the LFRS to detect, identify and evaluate the first traces of crystallization in comparison with high-frequency regions where internal vibration bands are detected. This analysis reveals that amorphous IMC prepared by cryogrinding instantaneously partially crystallizes at room temperature in the stable γ phase, well below T_g = 43 °C. A method based on the treatment of the LFRS to determine precise and very low volume of crystallized material within amorphous matrix is described and used to analyze the crystallization kinetics of ground amorphous IMC powder. This study demonstrates that Raman spectroscopy is also a well-adapted technique to point out small amount of amorphous state in crystalline matrix. Crystallization of ground IMC powder was also analyzed by isothermal microcalorimetry experiments, which is one of the most widely used methods to analyze isothermal crystallization and to evaluate crystallinity.     

The Use of Inverse Phase Gas Chromatography to Measure the Surface Energy of Crystalline,Amorphous, and Recently Milled Lactose

Purpose. To assess differences in surface energy due to processing induced disorder and to understand whether the disorder dominated the surfaces of particles. Methods. Inverse gas chromatography was used to compare the surface energies of crystalline, amorphous, and ball milled lactose. Results. The milling process made ca 1% of the lactose amorphous, however the dispersive contribution to surface energy was 31.2, 37.1, and 41.6 mJ m^–2 for crystalline, spray dried and milled lactose, respectively. A physical mixture of crystalline (99%) and amorphous (1%) material had a dispersive surface energy of 31.5 mJ m^–2. Conclusion. Milling had made the surface energy similar to that of the amorphous material in a manner that was very different to a physical mixture of the same amorphous content. The milled material will have similar interfacial interactions to the 100% amorphous material.     

Spectroscopic Characterization of Interactions Between PVP and Indomethacin in Amorphous Molecular Dispersions

Purpose. To study the molecular structure of indomethacin-PVP amorphous solid dispersions and identify any specific interactions between the components using vibrational spectroscopy. Methods. Solid dispersions of PVP and indomethacin were prepared using a solvent evaporation technique and IR and FT-Raman spectra were obtained. Results. A comparison of the carbonyl stretching region of indomethacin, known to form carboxylic acid dimers, with that of amorphous indomethacin indicated that the amorphous phase exists predominantly as dimers. The hydrogen bonding of indomethacin is not as dimers. Addition of PVP to amorphous indomethacin increased the intensity of the infrared band assigned to non-hydrogen bonded carbonyl. Con-comitantly, the PVP carbonyl stretch appeared at a lower wavenumber indicating hydrogen bonding. Model solvent systems aided spectral interpretation. The magnitude of the spectral changes were comparable for an indomethacin-PVP solid dispersion and a solution of indomethacin in methylpyrrolidone at the same weight percent. Conclusions. Indomethacin interacts with PVP in solid dispersions through hydrogen bonds formed between the drug hydroxyl and polymer carbonyl resulting in disruption of indomethacin dimers. PVP may influence the crystallisation kinetics by preventing the self association of indomethacin molecules. The similarity of results for solid dispersions and solutions emphasises the 'solution' nature of this binary amorphous state.     

Estimation of the Degree of Crystallinity of Cefazolin Sodium by X-Ray and Infrared Methods

The pentahydrate ( form) of cefazolin sodium (CEZ) exhibited sharp X-ray diffraction peaks, while the dehydrated form showed weak but distinct diffraction peaks. As expected the amorphous form exhibited a diffuse and halo diffraction pattern. The X-ray procedure to estimate the degree of crystallinity of CEZ was based upon the measurement of the total scattering and the scattering from the crystalline region of the drug. The major difference in the infrared (IR) spectra among the three forms of CEZ was the absence of a spectral band at 1542 cm^–1 in the amorphous form. The IR procedure was based upon the measurement of the peak percentage area ratio between the bands at 1542 and 1760 cm^–1, where the latter was used as a normalizing peak. The degree of crystallinity of CEZ samples, obtained by either freeze-drying aqueous CEZ solutions or storing the crystalline forms under different humidity conditions, was determined by these two methods. Although the correlation of results by the two methods was good, the X-ray procedure appears to be superior since it can differentiate among the three solid CEZ forms, whereas IR could distinguish between only crystalline and amorphous CEZ, reproducibly.     

Effect of different preparation methods on the dissolution behaviour of amorphous indomethacin

The aim of this study was to investigate whether amorphous indomethacin samples prepared using different preparative techniques and processing parameters exhibit different structural and thermodynamic characteristics and whether these differences can be correlated to their dissolution behaviour. Samples were prepared either by cooling the drug melt at different cooling rates or by cryo-milling the drug for different milling times. The resulting amorphous materials were characterised using X-ray diffraction, Raman spectroscopy and polarising light microscopy. All samples were entirely X-ray amorphous, except for the sample cryo-milled for 15 min, which exhibited residual crystallinity. The shape of the halos in the diffractograms, however, varied depending on the preparation method and processing parameters, suggesting structural variations in the near order of the molecules between the prepared amorphous forms. This finding was supported by principal component analysis of the Raman spectra, as the samples clustered in the scores plot according to processing parameters for both of the preparative methods used. When investigating the dissolution behaviour, the samples cooled at different cooling rates showed no significant differences in their dissolution profiles and dissolution rates (≈0.55 μg/ml/cm²). In contrast, for cryo-milled samples, dissolution rate depended on the milling time, with samples milled for 120, 180 and 240 min, showing significantly increased dissolution rates of 0.28, 0.48 and 0.59 μg/ml/cm², respectively, when compared to crystalline indomethacin (≈0.06 and 0.05 μg/ml/cm² for α and γ-indomethacin, respectively). The milling processes appear to continue to affect the degree of disorder in the solid material, enhancing its dissolution rate, although all samples milled for >30 min were X-ray amorphous. Thus, choosing the right preparation technique and parameters for preparing amorphous solids is critical for producing materials with enhanced dissolution profiles.     

Evaluation of Amorphous Ursodeoxycholic Acid by Thermal Methods

Purpose. The purpose of this study was to characterize the amorphous state of ursodeoxycholic acid (UDCA) samples by using isothermal microcalorimetry, X-ray diffraction, infrared (IR) spectroscopy and solid state carbon 13 nuclear magnetic resonance (¹³C-NMR) spectroscopy, and to demonstrate the application of the thermal methods (microcalorimetry and differential scanning calorimetry (DSC)) for studying the amorphous state and clarifying the dissolution mechanism of UDCA. Methods. Amorphous UDCA was prepared by grinding and rapid cooling of the melts. The heat of solution of UDCA was measured by an isothermal heat-conduction twin microcalorimeter at 25.0°C. Some physicochemical properties of amorphous UDCA were also studied. Results. The intensities of X-ray diffraction peaks of crystalline UDCA decreased with an increase in grinding time. The heat levels of solution of crystalline UDCA and UDCA ground for 1 min were endothermic, and became exothermic with an increase in grinding time. A good correlation was obtained between the heat of solution and the heat of crystallization determined from the peak area in DSC. Although no significant difference was observed in X-ray diffraction patterns of amorphous UDCA prepared by the two methods, significant differences were recognized in DSC, IR and ¹³C-NMR, and the heat of solution indicated different values among the two samples. The stability of amorphous UDCA samples stored under 74.5% relative humidity at 40°C was found to depend upon the preparation methods. Conclusions. Different states of amorphous UDCA were obtained depending on the preparation method. The application of thermal methods to evaluate the amorphous state was demonstrated. The mechanism of dissolution of UDCA was discussed from the results of the heat of solution examination.     

An In Situ Dissolution Study of Aspirin Crystal Planes (100) and (001) by Atomic Force Microscopy

Purpose. To observe in situ and on individual aspirin crystal faces the comparative rates and processes of dissolution of the dominant faces. Methods. The kinetics of the dissolution rate of two aspirin crystal planes (001) and (100) under 0.05M HCl are studied in situ at room temperature using Atomic Force Microscopy. The dissolution process of each crystal plane was followed by observed changes in topographic features. Results. The results revealed that crystal plane (001) dissolves by receding step edges, and has a dissolution rate of 0.45 nm s^–1. Conversely, plane (100) displays crystal terrace sinking at an average rate of 2.93 nm s^–1. Calculated intrinsic dissolution values (g s^–1 cm^–2) for planes (001) and (100) are 1.37 × 10^–7 g s^–1 cm^–2 and 8.36 × 10^–7 g s^–1 cm^–2, respectively. Conclusions. These values indicate that the rate of flux of material from plane (100) is approximately six times greater than that from plane (001), under 0.05M HCl. Interpretation of the data, based upon intrinsic dissolution rates and dissolution rate velocities, correlate with reported variations in the dissolution behavior of commercial aspirin products. These observations illustrate the suitability of the technique for characterizing the dissolution behavior of crystalline drugs.     

Evaluation of the Microcrystallinity of a Drug Substance,Indomethacin, in a Pharmaceutical Model Tablet by Chemometric FT-Raman Spectroscopy

Purpose To establish a chemometric method for the precise evaluation of the microcrystallinity of indomethacin (IMC) in a pharmaceutical model tablet, based on FT-Raman spectroscopy.Methods Standard sample powders of homogeneous mixtures of amorphous and crystalline IMC were prepared in various proportions. A calibration model for the crystallinity of IMC was constructed by partial least-square (PLS) analysis based on the multiplicative scatter correction (MSC) + second-derivative transformed Raman spectra. A calibration model for the crystallinity of IMC in a model pharmaceutical product (IMC/mannitol = 1:9 wt/wt) was also constructed using homogeneous standard sample powders of various degrees of crystallinity of IMC.Results This technique was validated to detect to 2% an amorphous or crystalline material in IMC contained in the model product (0.2% of the total mass of the tablet). Using this technique, not only pressure-induced amorphization but also the difference in microcrystallinity of IMC at the surface and interior of a model product tablet was elucidated after compaction of the tablet.Conclusions The established technique is ideally suited for precise quantification of microanalysis of drug substances and drug products, particularly at the surface and interior of the tablet.     

A Spectroscopic Investigation of Hydrogen Bond Patterns in Crystalline and Amorphous Phases in Dihydropyridine Calcium Channel Blockers

Purpose. To gain insight into the molecular structure of amorphous compounds by investigating hydrogen bonding patterns and strength in a series of structurally related compounds. Seven 1,4-dihydro- pyridine calcium channel blockers were evaluated. Methods. FT-Raman and FT-infrared spectra of the compounds in the crystalline and amorphous states were obtained. Results. For crystalline compounds, the position of the NH vibration varied considerably, indicating that the strength of hydrogen bonding differs between the different compounds in agreement with published single crystal X-ray data. For the amorphous phases, the NH vibration occurred at approximately the same position for all compounds, suggesting a uniform average hydrogen bonding strength. Somewhat surprisingly, for some compounds, the average hydrogen bond strength in the amorphous state was found to be greater than in the crystalline compound, although for others, it was weaker as anticipated. Hydrogen bonding patterns (acceptor group) varied between the crystalline compounds, but were remarkably consistent in the amorphous compounds; thus the acceptor group in the amorphous phase is not necessarily the same as in the crystalline counterpart. Conclusions. Hydrogen bond patterns and strength within a group of chemically related amorphous compounds were found to be very similar, but were different from those in the equivalent group of crystalline substances.     

Molecular Mobility of Supercooled Amorphous Indomethacin,Determined by Dynamic Mechanical Analysis

Purpose. To determine the viscosity and the frequency-dependent shear modulus of supercooled indomethacin as a function of temperature near and above its glass transition temperature and from these data to obtain a quantitative measure of its molecular mobility in the amorphous state. Methods. Viscoelastic measurements were carried with a controlled strain rheometer in the frequency domain, at 9 temperatures from 44° to 90°C. Results. The viscosity of supercooled indomethacin shows a strong non-Arrhenius temperature dependence over the temperature range studied, indicative of a fragile amorphous material. Application of the viscosity data to the VTF equation indicates a viscosity of 4.5 × 10¹⁰ Pa.s at the calorimetric Tg of 41°C, and a T₀ of –17°C. From the complex shear modulus and the Cole-Davidson equation the shear relaxation behaviour is found to be non-exponential, and the shear relaxation time at Tg is found to be approximately 100 sec. Conclusions. Supercooled indomethacin near and above its Tg exhibits significant molecular mobility, with relaxation times similar to the timescales covered in the handling and storage of pharmaceutical products.     

Quantitative determination of crystallinity of alpha-lactose monohydrate by Near Infrared Spectroscopy (NIRS)

The purpose of this study was to determine quantitatively the crystallinity in crystalline/amorphous powder mixtures of lactose, to asses the capability of Near Infrared Spectroscopy (NIRS) for quantitative determination of crystallinity and to compare the accuracy of the NIRS method with that of conventional X-ray powder diffraction (XRPD). Amorphous lactose was prepared by spray drying. Samples with different crystallinity were prepared by physical mixing of 100% amorphous and 100% crystalline materials. The samples were characterized by XRPD and NIRS. Analysis was performed on the data sets by multiple linear regression (MLR). There is a close correlation between the predicted and the actual crystallinity of physical mixtures of crystalline and amorphous lactose, determined by NIRS (R(2)=0.9994). NIRS results were compared to the XRPD using the same sample sets. The correlation coefficients was 0.9981. The results showed that NIRS is an useful method for accurately determining low quantities of the crystalline lactose in a physical mixture. Therefore, NIRS can be used for the quantitative determination of crystallinity of materials during pharmaceutical procedures.     

lontophoretic Delivery of Apomorphine II: An In Vivo Study in Patients with Parkinson's Disease

Purpose. Transdermal transport rates of the dopamine agonist R-apomorphine were determined in patients with idiopathic Parkinson's disease (IPD). Apomorphine was applied by iontophoresis at two current densities. Methods. In ten patients apomorphine was applied passively for one hour. Thereafter, in the first five patients, a current density of 250 A.cm^–2 was applied for one hour and a current density of 375 A.cm^–2 in the second group. The individual pharmacokinetic parameters were obtained separately following a 15-minute zero-order intravenous infusion of 30 g.kg^–1. Skin resistance was measured during current delivery. Current-induced irritation was measured by Laser Doppler Flowmetry (LDF). The pharmacodynamics were quantified by a unilateral tapping score. Qualitative clinical improvements (decreased tremor, rigidity or cramp) were also recorded. Results. In all patients increasing plasma concentrations of R-apomorphine were found during the interval of current application. The maximum concentrations that were attained were related to the applied current density: 1.3 ± 0.6 ng.ml^–1 at 250 A.cm^–2 and 2.5 ± 0.7 ng.ml^–1 at 375 A.cm^–2. When the current was switched off all concentrations returned to baseline values in about 90 minutes. By mathematical deconvolution of the profiles it was shown that steady-state fluxes were reached within the one-hour interval of current driven transport. Steady-state fluxes were calculated to be 69 ± 30 nmol.cm^–2.h^–1 at 250 A.cm^–2 and 114 ± 34 nmol.cm^–2.h^–1 at 375 A.cm^–2. Individual drug input rates were inversely related to the overall resistance. Significantly elevated LDF values were found after patch removal, indicating mild current induced erythema. Only subtherapeutic plasma concentrations were obtained in all patients except for one. Conclusions. The results show that current-dependent delivery of apomorphine is possible in vivo at acceptable levels of skin irritation. Excellent correlation was found between the calculatedin vivo transport rates and the rates that were previously obtained in vitro.     

Determination of free amino acid content in Radix Pseudostellariae using near infrared (NIR) spectroscopy and different multivariate calibrations

Near infrared (NIR) spectroscopy combined with multivariate calibration was attempted to analyze free amino acid content of Radix Pseudostellariae. The original spectra of Pseudostellariae samples in wavelength range of 10000–4000 cm⁻¹ were acquired. Partial least squares (PLS), kernel PLS (k-PLS), back propagation neural network (BP-NN), and support vector regression (SVR) algorithms were performed comparatively to develop calibration models. Some parameters of the calibration models were optimized by cross-validation. The performance of BP-NN model was better than PLS, k-PLS, and SVR models. The root mean square error of prediction (RMSEP) and the correlation coefficient (R) of BP-NN model were 0.687 and 0.889 in prediction set respectively. Results showed that NIR spectroscopy combined with multivariate calibration has significant potential in quantitative analysis of free amino acid content in Radix Pseudostellariae.     

Phase Behavior of Binary and Ternary Amorphous Mixtures Containing Indomethacin, Citric Acid, and PVP

Purpose. To better understand the nature of drug-excipient interactions we have studied the phase behavior of amorphous binary and ternary mixtures of citric acid, indomethacin and PVP, as model systems. Methods. We have prepared amorphous mixtures by co-melting or coprecipitation from solvents, and have measured glass transition temperatures with differential scanning calorimetry. Results. Citric acid and indomethacin in the amorphous state are miscible up to 0.25 weight fraction of citric acid, equivalent to about 2 moles of citric acid and 3 moles of indomethacin. Phase separation, as reflected by two Tg values, occurs without crystallization leading to a saturated citric acid-indomethacin amorphous phase and one essentially containing only citric acid. PVP-citric acid and PVP-indomethacin form non-ideal miscible systems at all compositions. A ternary system containing 0.3 weight fraction of PVP produces a completely miscible system at all citric acid-indomethacin compositions. The use of 0.2 weight fraction of PVP, however, only produces miscibility up to a weight fraction of 0.4 citric acid relative to indomethacin. The two phases above this point appear to contain citric acid in PVP and citric acid in indomethacin, respectively. Conclusions. Two components of an amorphous solid mixture containing citric acid and indomethacin with limited solid state miscibility can be solublized as an amorphous solid phase by the addition of moderate levels of PVP.     

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, α-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.     

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.     

Effect of Gelation on the Chemical Stability and Conformation of Leuprolide

Purpose. The purpose of this study was to characterize the conformation, aggregation, and stability of leuprolide on gelation. Methods. Infrared spectra (FTIR) of leuprolide solutions and gels were collected in water, propylene glycol (PG), dimethyl sulfoxide (DMSO), and trifluoroethanol (TFE). Leuprolide solution and gel stability data were obtained by SEC and RP-HPLC. Results. Leuprolide was induced to gel with increasing peptide concentration, introduction of salts, and gentle agitation. Leuprolide dissolved in water (400 mg/ml) demonstrated FTIR spectra consisting of two major bands of equal intensity at 1615 cm^–1 and 1630 cm^–1, similar to inter- and intra-molecular -sheet structure in proteins. When samples were gently agitated for 24 hours at 25°C, the formulation was observed to change from a viscous liquid to an opaque gel with a concomitant shift in infrared spectra from the equal intensity bands to mostly 1630 cm^–1, indicating a shift to a preferred -sheet structure. Incubation of leuprolide with 20–200 mM salts at 25°C and 37°C also produced gels ranging from clear to cloudy and stringy white precipitates. The gel and precipitate were marked by a shift of the predominant p-sheet band to 1630 cm^–1 and 1615 cm^–1, respectively. Leuprolide was also observed to gel and/or precipitate in mixtures of water, PG or TFE, but not in DMSO. Conclusions. Birefringence was noted in many of the firmer gels. Both solutions and gels demonstrated minimal dimer or trimer formation, with no larger order aggregates detected. The chemical stability profile of gelled leuprolide was similar to that of the non-gelled water formulation by RP-HPLC.     

The Molecular Mobility of Supercooled Amorphous Indomethacin as a Function of Temperature and Relative Humidity

Purpose. To determine the relaxation times of supercooled indomethacin as a function of temperature and relative humidity above Tg, and to analyze the results in the context of being able to predict such behavior at various storage conditions. Methods. Dielectric relaxation times were measured in the frequency domain (12 to 10⁵ Hz) for amorphous indomethacin equilibrated at 0, 56, and 83% relative humidity. The heating rate dependence of Tg for dry supercooled indomethacin was measured with differential scanning calorimetry and used to determine relaxation times. The results were compared with previously published shear relaxation times and enthalpy recovery data. Results. Very good agreement was observed between dielectric and shear relaxation times, and those obtained from the heating rate dependence of the Tg, for dry indomethacin as a function of temperature above Tg. The introduction of water lowered the dielectric relaxation times of supercooled indomethacin without significantly affecting its fragility. The relaxation times below Tg, found to be lower than those predicted by extrapolation of the data obtained above Tg, were analyzed in the context of the Adam-Gibbs-Vogel equation. Conclusions. The relaxation times of amorphous indomethacin obtained from the heating rate dependence of Tg were in good agreement with those obtained from shear and dielectric measurements, thus validating a relatively simple approach of assessing molecular mobility. The significant molecular mobility of amorphous indomethacin observed below Tg, and the significant plasticizing effects of sorbed water, help to explain why amorphous indomethacin crystallizes well below Tg over relatively short time scales.