Physicochemical properties of amorphous clarithromycin obtained by grinding and spray drying

Influence of Milling Process on Efavirenz Solubility

Introduction:

The aim of this study was to investigate the influence of the milling process on the solubility of efavirenz.

Materials and Methods:

Milling process was done using Nanomilling for 30, 60, and 180 min. Intact and milled efavirenz were characterized by powder X-ray diffraction, scanning electron microscopy (SEM), spectroscopy infrared (IR), differential scanning calorimetry (DSC), and solubility test.

Results:

The X-ray diffractogram showed a decline on peak intensity of milled efavirenz compared to intact efavirenz. The SEM graph depicted the change from crystalline to amorphous habit after milling process. The IR spectrum showed there was no difference between intact and milled efavirenz. Thermal analysis which performed by DSC showed a reduction on endothermic peak after milling process which related to decreasing of crystallinity. Solubility test of intact and milled efavirenz was conducted in distilled water free CO₂ with 0.25% sodium lauryl sulfate media and measured using high-performance liquid chromatography method with acetonitrile: distilled water (80:20) as mobile phases. The solubility was significantly increased (P < 0.05) after milling processes, which the intact efavirenz was 27.12 ± 2.05, while the milled efavirenz for 30, 60, and 180 min were 75.53 ± 1.59, 82.34 ± 1.23, and 104.75 ± 0.96 μg/mL, respectively.

Conclusions:

Based on the results, the solubility of efavirenz improved after milling process.

The effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding

In this study, the effect of structurally related impurities on crystallinity reduction of sulfamethazine by grinding was evaluated. The crystallinity of sulfamethazine was not decreased when it was ground alone. However, when structurally related impurities with sulfonamide derivatives were blended, the crystallinity of sulfamethazine was decreased by grinding. Other materials without a sulfonamide moiety showed no such effect. The Raman spectra of sulfamethazine demonstrated that there was a difference between its crystalline and amorphous states within its sulfonamide structure. It was suggested that the sulfonamide structure of the impurities was important in causing the inhibition of recrystallization of sulfamethazine during grinding.

Implications of designing clarithromycin loaded solid lipid nanoparticles on their pharmacokinetics, antibacterial activity and safety

The major obstacles for treatment of intracellular infections with clarithromycin are poor gastrointestinal solubility, short half-life (3–4 h), low oral bioavailability and hepatotoxicity.

Understanding pharmaceutical polymorphic transformations II: crystallization variables and influence on dosage forms

Excipients or formulation variables have often been exploited to improve stability, modify release, or improve physicochemical properties of dosage forms. In pharmaceutical field, it is generally expected that excipients work at macromolecular level where they might influence the crystal structure of a solid. These polymers/colloidal particles may modify the rate and direction of crystal growth. It has also been observed, that different polymorphic crystals exhibit different colors on exposure to same colorant, predominantly due to difference in surface pH of different crystal lattices. Apart from physicochemical affect, crystal habit also influences pharmacokinetic parameters of the dosage form. Crystals with smaller size or lower lattice energy have shown to exhibit higher bioavailability with faster rate of release.

Understanding pharmaceutical polymorphic transformations I: influence of process variables and storage conditions

The active pharmaceutical ingredient (API) of a dosage form is affected by number of mechanical and environmental factors which have a tendency to alter its crystalline state. Polymorphic transitions have been observed to occur during various unit operations like granulation, milling and compression. Forces of pressure, shear and temperature have an ability to induce alterations in crystal habit. A conversion in polymorphic form during a unit operation is very likely to affect the handling of API in the subsequent unit operation. Transitions have also been observed during storage of formulations where the relative humidity and temperature play a major role. An increase in temperature during storage can dehydrate or desolvate the crystal and hence produce crystal defects, whilst, high humidity conditions produce higher molecular mobility leading to either crystallization of API or alteration of its crystalline form.

Enhanced oral bioavailability of fenofibrate using polymeric nanoparticulated systems: physicochemical characterization and in vivo investigation

Background

The intention of this research was to prepare and compare various solubility-enhancing nanoparticulated systems in order to select a nanoparticulated formulation with the most improved oral bioavailability of poorly water-soluble fenofibrate.

Methods

The most appropriate excipients for different nanoparticulated preparations were selected by determining the drug solubility in 1% (w/v) aqueous solutions of each carrier. The polyvinylpyrrolidone (PVP) nanospheres, hydroxypropyl-β-cyclodextrin (HP-β-CD) nanocorpuscles, and gelatin nanocapsules were formulated as fenofibrate/PVP/sodium lauryl sulfate (SLS), fenofibrate/HP-β-CD, and fenofibrate/gelatin at the optimized weight ratios of 2.5:4.5:1, 1:4, and 1:8, respectively. The three solid-state products were achieved using the solvent-evaporation method through the spray-drying technique. The physicochemical characterization of these nanoparticles was accomplished by powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Their physicochemical properties, aqueous solubility, dissolution rate, and pharmacokinetics in rats were investigated in comparison with the drug powder.

Results

Among the tested carriers, PVP, HP-β-CD, gelatin, and SLS showed better solubility and were selected as the most appropriate constituents for various nanoparticulated systems. All of the formulations significantly improved the aqueous solubility, dissolution rate, and oral bioavailability of fenofibrate compared to the drug powder. The drug was present in the amorphous form in HP-β-CD nanocorpuscles; however, in other formulations, it existed in the crystalline state with a reduced intensity. The aqueous solubility and dissolution rates of the nanoparticles (after 30 minutes) were not significantly different from one another. Among the nanoparticulated systems tested in this study, the initial dissolution rates (up to 10 minutes) were higher with the PVP nanospheres and HP-β-CD nanocorpuscles; however, neither of them resulted in the highest oral bioavailability. Irrespective of relatively retarded dissolution rate, gelatin nanocapsules showed the highest apparent aqueous solubility and furnished the most improved oral bioavailability of the drug (~5.5-fold), owing to better wetting and diminution in crystallinity.

Conclusion

Fenofibrate-loaded gelatin nanocapsules prepared using the solvent-evaporation method through the spray-drying technique could be a potential oral pharmaceutical product for administering the poorly water-soluble fenofibrate with an enhanced bioavailability.

The dissolution and solid-state behaviours of coground ibuprofen-glucosamine HCl

The cogrinding technique is one of most effective methods for improving the dissolution of poorly water-soluble drugs and it is superior to other approaches from an economical as well as an environmental standpoint, as the technique does not require any toxic organic solvents. Present work explores the role of d-glucosamine HCl (GL) as a potential excipient to improve dissolution of a low melting point drug, ibuprofen (Ibu), using physical mixtures and coground formulations. The dissolution of the poorly soluble drug has been improved by changing the ratio of Ibu:GL and also grinding time. The results also showed that although GL can enhance the solubility of Ibu, it also reduces pH around the Ibu particles which led to poor dissolution performance when the concentration of GL is high. The effect of GL on the solubility of Ibu could be misleading if the pH of the final solution was not measured. Grinding reduced the particle size of GL significantly but in case of Ibu it was less effective. Solid state analysis (XRPD, DSC, and FT-IR) showed that ibuprofen is stable under grinding conditions, but the presence of high concentration of GL in samples subjected to high grinding times caused changes in FT-IR spectrum of Ibu which could be due to intermolecular hydrogen bond or esterification between the carboxylic acid group in the ibuprofen and hydroxyl group in the GL.

Enhanced solubility and intestinal absorption of candesartan cilexetil solid dispersions using everted rat intestinal sacs

OBJECTIVE

Candesartan cilexetil (CAN) is a poor aqueous soluble compound and a P-glycoprotein (P-gp) efflux pump substrate. These key factors are responsible for its incomplete intestinal absorption.

METHODS

In this study, we investigated to enhance the absorption of CAN by improving its solubility and inhibiting intestinal P-gp activity. A phase solubility method was used to evaluate the aqueous solubility of CAN in PVP K30 (0.2-2%). Gibbs free energy [Formula: see text] values were all negative. Solubility was enhanced by the freeze drying technique. The in vitro dissolution was evaluated using the USP paddle method. The interaction between drug and carrier was evaluated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Differential scanning calorimetry (DSC) studies. Naringin was selected as P-gp inhibitor. Absorption studies were performed using the everted gut sac model from rat jejunum. The drug analysis was performed by HPLC.

RESULTS

FTIR spectra revealed no interaction between drug and PVP K30. From XRD and DSC data, CAN was in the amorphous form, which explains the cumulative release of drug from its prepared systems. We noticed an enhancement of CAN absorption by improving its solubility and inhibiting the P-gp activity. The significant results (p < 0.05) were obtained for freeze dried solid dispersions in the presence of P-gp inhibitor than without naringin (15 mg/kg) with an absorption enhancement of 8-fold.

CONCLUSION

Naringin, a natural flavonoid, has no undesirable side effects. Therefore, it could be employed as an excipient in the form of solid dispersions to increase CAN intestinal absorption and its oral bioavailability.

A new way of stabilization of furosemide upon cryogenic grinding by using acylated saccharides matrices. The role of hydrogen bonds in decomposition mechanism

Recently it was reported that upon mechanical milling of pure furosemide significant chemical degradation occurs (Adrjanowicz et al. Pharm. Res.2011, 28, 3220-3236). In this paper, we present a novel way of chemical stabilization amorphous furosemide against decomposing that occur during mechanical treatment by preparing binary mixtures with acylated saccharides. To get some insight into the mechanism of chemical degradation of furosemide induced by cryomilling, experimental investigations supported by density functional theory (DFT) computations were carried out. This included detailed studies on molecular dynamics and physical properties of cryoground samples. The main thrust of our paper is that we have shown that furosemide cryomilled with acylated saccharides forms chemically and physically stable homogeneous mixtures with only one glass transition temperature, Tg. Finally, solubility measurements have demonstrated that furosemide cryomilled with acylated saccharides (glucose, maltose and sucrose) is much more soluble with respect to the crystalline form of this active pharmaceutical ingredient (API).

Crystallinity evaluation of tacrolimus solid dispersions by chemometric analysis

Different destructive and nondestructive analytical methods, namely powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), Raman and near-infrared (NIR) spectroscopy and imaging, to detect and characterize tacrolimus trace crystallinity in an amorphous solid dispersion (SD) using chemometric analysis were developed. The SD was spiked with different percentages of the crystalline drug to construct an array of SDs with different crystallinity percentages. Partial least square (PLS) regression analysis was employed to compare the performance of the calibration models created using these analytical methods. The obtained results indicated a significant interaction between tacrolimus and the employed polymer and a drug dissolution dependency on the crystalline fraction within the SDs. Using two PLS factors, these analytical methods were ranked according to its specificity to detect the trace crystallinity of SDs as NIR>PXRD>Raman>DSC. Through the application of PLS, root-mean-squared error of calibration values of 2.91%, 5.36%, 7.07% and 11.58% were calculated for the calibration models constructed by NIR, PXRD, Raman and DSC, respectively. Having a prediction error of 2.1% and a correlation coefficient of 0.99, it is demonstrated that combined NIR imaging and chemometric analysis outperformed the other methods in detecting trace crystallinity in tacrolimus amorphous systems. The spatial distributions of amorphous and crystalline drug were also obtained in order to allow for studying the crystallization dissemination in the solid dispersions. Consequently, NIR and NIR imaging coupled with chemometry was shown to be a powerful tool for the prediction of drug crystallinity within SDs.

Thermal insight of mechanically activated bile acid powders

Mechanical activation of pharmaceutical materials presents an important but poorly understood phenomenon of milled molecular crystals. In this work, a strategy was followed in an effort to understand this phenomenon, cryo-milled of both crystalline and amorphous counterpart of bile acids materials were characterized by X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC). The XRPD results for the 30-min milled crystalline powders displayed a characteristic amorphous halo patterns for all compounds tested. The DSC thermograms exhibited the typical glass transition temperatures (T(g)) associated with amorphous but only for two materials. For the remaining four milled compounds, a rather interesting behavior was manifested through a characteristic exothermal bimodal peak. The findings seemed to suggest that the occurrence of this event was not related to the (T(g)), but likely to the melting temperature (T(m)). The DSC results for the melt-quenched (amorphous) ursodeoxycholic acid after cryo-milling revealed that the material crystallized after the influence of the mechanical stress, and a bimodal peak was also observed similar to that of the cryo-milled crystalline material. It is contemplated that the response of the physical instability of the disordered phase could be explained either by the result of surface crystallization kinetics which is different from that of the bulk crystallization, or by the creation of supersaturated dislocated crystal prior to amorphization.

Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR

The purpose of this study was to elaborate the relationship between the (13)C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 degrees C/94% RH was evaluated by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, (13)C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the (13)C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The (13)C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.

Kinetic solubility and dissolution velocity of rutin nanocrystals

Lyophilized rutin nanocrystals were intensively evaluated regarding their physicochemical properties with respect to particle size analyses, crystallinity, kinetic solubility and dissolution behavior. The particle size was determined by photon correlation spectroscopy (PCS) and laser diffraction (LD). DSC and X-ray diffraction were used to study the crystalline state of rutin nanocrystals. In a period of 1 week, the kinetic solubility was determined using a shaker at 25 degrees C. DSC and X-ray diffraction analyses showed that lyophilized rutin nanocrystals prepared by high pressure homogenization remained in crystalline state. Lyophilized rutin nanocrystals could be re-dispersed completely in water and the kinetic solubility in water increased to 133 microg/ml.. Lyophilized rutin nanocrystals were almost completely dissolved within 15 min in water, buffer of pH 1.2 and buffer of pH 6.8. In contrast, only 70% of rutin raw material (rutin microcrystals) was dissolved within 15 min. The superior physicochemical properties of rutin nanocrystals should overcome the absorption problem in the gastrointestinal tract and increase the bioavailability.

Amorphization alone does not account for the enhancement of solubility of drug co-ground with silicate: the case of indomethacin

The solubility advantage of indomethacin amorphized by co-grinding with Neusilin US2 in various media was investigated. Physical mixtures of gamma-indomethacin and Neusilin US2 (in the ratios 1:1, 1:4 and 1:5) were amorphized at room temperature employing 75% RH in a porcelain jar mill using zirconia balls. The crystallinity of the samples was determined using ATR-FTIR and PXRD. The solubility and dissolution profiles of co-ground powders and crystalline counterparts were evaluated in 0.1 N HCl, water and phosphate buffer (pH 6.8) in a USP type II dissolution apparatus at 250 rpm and 37 degrees C. Very high concentrations of dissolved indomethacin as compared to the solubility of gamma-indomethacin (approximately 500 times in water and approximately 3.7 times in phosphate buffer) were attained. However, the presence of other polymorphs detected by PXRD and a change in the pH of the medium made interpretation of the results difficult. In 0.1 N HCl the solubility (i.e., the peak in a concentration versus time plot) of the amorphized drug in a 1:5 ratio with Neusilin increased to 109 times the solubility of crystalline gamma-indomethacin alone. An increase in amount of drug and Neusilin in the same ratio added to the dissolution medium also increased peak and plateau dissolution concentrations. The presence of silicic acid and ions (Mg(2+) and Al(3+)) in the dissolution media were found to cause the increase in the plateau concentration of indomethacin. Amorphization alone does not account for all of the dissolution enhancement; acidity, ions, and silicic acid are major contributors to dissolution enhancement.

Preparation of prolonged release clarithromycin microparticles for oral use and theirin vitro evaluation

Prolonged release microparticles of clarithromycin (CL) were prepared using Eudragit RL 100 and RS 100 by spray-drying and casting-drying techniques. For the characterization of those microparticles, preparation yield, particle size distribution, X-ray diffraction, thermal behavior, active agent content and in vitro dissolution from the microparticles were performed. HPLC was used for the assay of clarithromycin and the assay method was validated. All the formulations obtained showed prolonged release when compared to pure clarithromycin. Microparticles prepared by spray-drying method had a slower release compared to those of casting-drying method. Spray-drying method seems to be a more suitable method to prepare microparticles for prolongation in release.

Amorphization of Indomethacin by Co-Grinding with Neusilin US2: amorphization kinetics, physical stability and mechanism

PURPOSE

To quantify the effects of the ratio of indomethacin to Neusilin US2 and the processing humidity on the amorphization kinetics, stability and nature of the interaction.

MATERIALS AND METHODS

A porcelain jar mill with zirconia balls was used to affect conversion of the physical mixtures (48 g) of indomethacin and Neusilin US2 (in the ratios 1:1 to 1:5) to amorphous states at room temperature (25 degrees C) employing either 0% RH or 75% RH. The percent crystallinity in the samples was determined from ATR-FTIR scans chemometrically. The physical stability of these co-ground amorphous powders was evaluated at 40 degrees C/75% RH and 40 degrees C/0% RH.

RESULTS

The lower the ratio of indomethacin to Neusilin US2, the faster is the amorphization during co-grinding. Higher humidity facilitates amorphization with a more pronounced effect at the lower ratio of indomethacin to Neusilin US2. There is further amorphization of some of the partially amorphized samples on storage at 40 degrees C/75% RH for 3 months. Hydrogen bonding and surface interaction between metal ions of Neusilin US2 and indomethacin can explain changes in the FTIR spectra.

CONCLUSIONS

The processing humidity and the ratio of indomethacin to Neusilin US2 are important factors to be considered to affect amorphization during ball milling. Amorphous indomethacin can be stabilized by co-grinding with Neusilin US2.

Thermodynamic and kinetic characterization of polymorphic transformation of famotidine during grinding

Two polymorphs of famotidine were prepared by recrystallization from acetonitrile for form A and methanol for form B, respectively. The effect of grinding process on the polymorphic transformation of famotidine was investigated. Each famotidine sample ground for various grinding times in a ceramic mortar was determined by differential scanning calorimetry (DSC), conventional and thermal Fourier transform infrared (FT-IR) microspectroscopy. The results indicate that the raw material of famotidine was proved to be a form B. A unique IR absorption band at 3505 cm(-1) for famotidine form B gradually decreased its intensity with the grinding time, while two newer IR absorption bands at 3451 and 1671 cm(-1) for famotidine form A slowly appeared. The peak intensity ratio of 3451/350 5 cm(-1) was linearly (r=0.9901) increased with the grinding time, suggesting that the grinding process could induce the polymorphic transformation of famotidine from form B to form A by a zero-order process. The DSC endothermic peaks also confirmed this polymorphic transformation from famotidine form B (167 degrees C, DeltaH: 165J/g) to famotidine form A (174 degrees C, DeltaH: 148J/g) in which the values of enthalpy were linearly reduced with the increase of grinding time (r=0.9943). The phase transition temperature of the different ground famotidine samples could be easily and only evidenced by using thermal FT-IR microspectroscopy, rather than by DSC analysis. These phase transition temperatures of the famotidine form B ground for 5-20 min quickly reduced from 144 to 134 degrees C and maintained a constant at 134 degrees C even after 20-30 min grinding. The grinding process not only decreased the crystallinity of famotidine form B but also reduced the particle size of famotidine form B, resulting in easy induction of the polymorphic transformation of famotidine from form B to form A in ground famotidine sample.

Precision and detection limit of quality test for amorphous drug in powder X-ray diffractometry

This report puts forward a method of powder X-ray diffractometry to estimate the precision and detection limit of the crystalline component in an amorphous drug. Cefditoren pivoxil (CP) was employed as a model drug. The major error source of the measurement at low crystal contents is shown to be the random noise in a diffraction pattern (halo pattern) of the amorphous material. For the analysis of the noise, the obstructive halo pattern should be eliminated from the observed pattern. The subtraction of the observed halo pattern from another one derived from the same material, extracts the random noise alone, although the noise is amplified by square root 2 times. The noise in the powder X-ray diffractometry was identified as the white noise. On the basis of the stochastic properties of the extracted noise and signal parameters (peak area) of CP, the relative standard deviations (R.S.D.) of the area measurements of the crystalline diffraction peaks were estimated over a wide range of crystal contents without repeated experiments. The detection limit was determined such that the crystal content at detection limit produced 30% R.S.D. of the measurements. The R.S.D. and detection limit obtained from FUMI theory were in good agreement with the results from the repeated measurements.