Temperature- and moisture-induced crystallization of amorphous lactose in composite particles with sodium alginate prepared by spray-drying

Effect of Polymers and Storage Relative Humidity on Amorphous Rebamipide and Its Solid Dispersion Transformation: Multiple Spectra Chemometrics of Powder X-Ray Diffraction and Near-Infrared Spectroscopy

This study aimed to investigate the effect of polymers and storage relative humidity on amorphous rebamipide (RB) and its solid dispersion phase transformation using chemometrics based on multiple datasets. The amorphous RB was prepared using particle mixture and grinding methods with hydroxypropyl cellulose, polyvinylpyrrolidone, and sodium dodecyl sulfate. Prepared amorphous RB and solid dispersion samples were stored under a relative humidity of 30% and 75% for four weeks. Infrared spectra of the dispersion samples suggested that the hydrogen bond network was constructed among quinolinone, carbonyl acid, and amide of RB and other polymers. The dataset combining near-infrared (NIR) spectra and powder X-ray diffractograms were applied to principal component analysis (PCA). The relationship between diffractograms and NIR spectra was evaluated using loadings and the PCA score. The multiple spectra analysis is useful for evaluating model amorphous active pharmaceutical ingredients without a standard sample.

Physicochemical characterization and water vapor sorption of organic solution advanced spray-dried inhalable trehalose microparticles and nanoparticles for targeted dry powder pulmonary inhalation delivery

Novel advanced spray-dried inhalable trehalose microparticulate/nanoparticulate powders with low water content were successfully produced by organic solution advanced spray drying from dilute solution under various spray-drying conditions. Laser diffraction was used to determine the volumetric particle size and size distribution. Particle morphology and surface morphology was imaged and examined by scanning electron microscopy. Hot-stage microscopy was used to visualize the presence/absence of birefringency before and following particle engineering design pharmaceutical processing, as well as phase transition behavior upon heating. Water content in the solid state was quantified by Karl Fisher (KF) coulometric titration. Solid-state phase transitions and degree of molecular order were examined by differential scanning calorimetry (DSC) and powder X-ray diffraction, respectively. Scanning electron microscopy showed a correlation between particle morphology, surface morphology, and spray drying pump rate. All advanced spray-dried microparticulate/nanoparticulate trehalose powders were in the respirable size range and exhibited a unimodal distribution. All spray-dried powders had very low water content, as quantified by KF. The absence of crystallinity in spray-dried particles was reflected in the powder X-ray diffractograms and confirmed by thermal analysis. DSC thermal analysis indicated that the novel advanced spray-dried inhalable trehalose microparticles and nanoparticles exhibited a clear glass transition (T(g)). This is consistent with the formation of the amorphous glassy state. Spray-dried amorphous glassy trehalose inhalable microparticles and nanoparticles exhibited vapor-induced (lyotropic) phase transitions with varying levels of relative humidity as measured by gravimetric vapor sorption at 25°C and 37°C.

Current Perspectives of Solubilization: Potential for Improved Bioavailability

This review focuses on the recent techniques of solubilization for the attainment of effective absorption and improved bioavailability. Solubilization may be affected due to cosolvent water interaction or altered crystal structure by cosolvent addition. Micellar solubilization could be affected by both ionic strength and pH. Addition of cosolvents to the surfactant solutions offers only a small advantage because of the decrease in the solubilization capacity of the micelles. Polymorphism is known to influence dissolution and bioavailability of the drugs. Molecular modeling study of cyclodextrin inclusion complexations can predict the inclusion modes, stoichiometry of the complex, and the relative complexing efficiency of cyclodextrins with various drug molecules.

Ability of Polyvinylpyrrolidone and Polyacrylic Acid to Inhibit the Crystallization of Amorphous Acetaminophen

The inhibition of crystallization of amorphous acetaminophen (ACTA) by polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) was studied using amorphous solid dispersions prepared by melt quenching. Co-melting with PVP and PAA decreased the average molecular mobility, as indicated by increases in glass transition temperature and enthalpy relaxation time. The ACTA/PAA dispersion exhibited much slower crystallization than the ACTA/PVP dispersion with a similar glass transition temperature value, indicating that interaction between ACTA and polymers also contributed to the stabilizing effect of these polymers. The carboxyl group of PAA may interact with the hydroxyl group of ACTA more intensely than the carbonyl group of PVP does, resulting in the stronger stabilizing effect of PAA. Dielectric relaxation spectroscopy showed that the number of water molecules tightly binding to PVP per monomer unit was larger than that to PAA. Furthermore, a small amount of absorbed water decreased the stabilizing effect of PVP, but not that of PAA. These findings suggest that the stronger stabilizing effect of PAA is due to the stronger interaction with ACTA. The ability of PAA to decrease the molecular mobility of solid dispersion was also larger than that of PVP, as indicated by the longer enthalpy relaxation time.

Molecular mobility‐based estimation of the crystallization rates of amorphous nifedipine and phenobarbital in poly(vinylpyrrolidone) solid dispersions

The overall crystallization rates and mean relaxation times of amorphous nifedipine and phenobarbital in the presence of poly(vinylpyrrolidone) (PVP) were determined at various temperatures to gain further insight into the effect of molecular mobility on the crystallization rates of amorphous drugs and the possibility of predicting stability from their molecular mobility. Nifedipine-PVP (9:1 w/w) and phenobarbital-PVP (95:5 w/w) solid dispersions were prepared by melting and rapidly cooling mixtures of each drug and PVP. The amount of amorphous nifedipine remaining in the solid dispersion was calculated from the heat of crystallization,which was obtained by differential scanning calorimetry. The amount of amorphous phenobarbital remaining in the solid dispersion was estimated from the change in the heat capacity at its glass transition temperature (T(g)). The time required for the amount of amorphous drug remaining to fall to 90% (t(90)) was calculated from the profile of time versus the amount of amorphous drug remaining. The t(90) values for the solid dispersions studied were 100-1000 times longer than those of pure amorphous drugs when compared at the same temperature. Enthalpy relaxation of the amorphous drugs in the solid dispersions was reduced compared with that in the pure amorphous drugs, indicating that the molecular mobility of the amorphous drugs is reduced in the presence of PVP. The temperature dependence of mean relaxation time (tau) for the nifedipine-PVP solid dispersion was calculated using the Adam-Gibbs-Vogel equation. Parameters D and T(0) in this equation were estimated from the heating rate dependence of T(g). Similar temperature dependence was observed for t(90) and tau values of the solid dispersion, indicating that the information on the temperature dependence of the molecular mobility, along with the crystallization data obtained at around the T(g), are useful for estimating the t(90) of overall crystallization at temperatures below T(g) in the presence of excipients.

Effect of Moisture on Impact Toughness of Sugar-Coated Tablets Manufactured by the Dusting Method

The purpose of this study was to clarify the effect of moisture on the impact toughness of sugar-coated tablets manufactured by the dusting method. We demonstrated that moisture plays an important role in the impact toughness of sugar-coated tablets. Moisturizing the sugar-coating layer resulted in enhancement of impact toughness of sugar-coated tablets, while reducing moisture in the sugar-coating layer resulted in weakening of the impact toughness. This was due to the characteristics of sucrose, the main ingredient of the sugar-coating layer, which is a soft and non-fragile material at high moisture levels, but hard and fragile at low moisture levels. We also demonstrated that friability as an indicator of impact toughness changed with time, and friability should be measured at 14 d after manufacture. This is due to moisture movement from outer sugar-coating layer into the inner sugar-coated tablets. Incorporating microcrystalline cellulose (MCC) in the subcoating layer resulted in sugar-coating layers with high resistance against impact even though moisture content of sugar-coated tablets was low. We confirmed the high impact toughness of the sugar-coated tablets with MCC whose moisture content was low from the results of both free fall and friability tests. We suggest that the dusting method using dusting powder containing MCC is a useful method for the production of sugar-coated tablets containing moisture sensitive drugs.

Effect of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone)

PURPOSE

The aim was to investigate the influence of polymer content and molecular weight on the morphology and heat- and moisture-induced transformations, as indicators of stability, of spray-dried composite particles of amorphous lactose and poly(vinylpyrrolidone) (PVP).

METHODS

Amorphous lactose and composite particles of amorphous lactose with different contents and molecular weights of PVP were prepared by spray drying. The nanostructure of the particles was analyzed by x-ray powder diffractometry, the morphology by light microscopy and SEM, the glass transition temperatures (Tg), crystallization temperatures (Tc), heats of crystallization and melting temperatures by differential scanning calorimetry, and moisture-induced crystallizations gravimetrically and by microcalorimetry.

RESULTS

All the types of particles prepared were amorphous. The Tg was unchanged or only marginally increased as a result of the inclusion of PVP. However, crystallization temperature, time to moisture-induced crystallization, and particle morphology were affected by both content and molecular weight of PVP.

CONCLUSIONS

Increased content and molecular weight of PVP may have the potential to increase the physical stability of amorphous lactose. However, Tg seems not to be a relevant indicator for the stability of this type of amorphous composite materials.

Physical stability of solid dispersions of the antiviral agent UC-781 with PEG 6000, Gelucire 44/14 and PVP K30

This paper describes the physical stability of solid dispersions of UC-781 with PEG 6000, Gelucire 44/14 and PVP K30 prepared by the solvent and melting methods. The concentration of the drug in the solid dispersions ranged from 5 to 80% w/w. The solid dispersions were stored at 4-8 and 25 degrees C (25% RH), then their physicochemical properties were analysed by differential scanning calorimetry (DSC), X-ray powder diffraction and dissolution studies as a function of storage time. The DSC curves of solid dispersions of UC-781 with PVP K30 did not show any melting peaks corresponding to UC-781 after storage, indicating no recrystallization of the drug. The DSC data obtained from PEG 6000 and Gelucire 44/14 showed some variations in melting peak temperatures and enthalpy of fusion of the carriers. It was shown that the enthalpy of fusion of PEG 6000 in the dispersions increased after storage; it was more pronounced for samples stored at 25 degrees C compared to those at 4-8 degrees C indicating the reorganization of the crystalline domains of the polymer. Similarly, the enthalpy of fusion of Gelucire 44/14 in the solid dispersions increased as a function of time. Dissolution of UC-781 from all solid dispersions decreased as a function of storage time. While these observations concurred with the DSC data for all solid dispersions, they were not reflected by X-ray powder diffraction data. It was concluded that it is the change of the physical state of the carriers and not that of the drug, which is responsible for the decreased dissolution properties of the solid dispersions investigated.