Changes in surface properties by granulation and physicochemical stability of granulated amorphous cefditoren pivoxil with additives

Characterization of Co-amorphous Carvedilol-Maleic Acid System Prepared by Solvent Evaporation

The aim of this study was to enhance the solubility and stability of the water-insoluble drug carvedilol (CAR) with maleic acid (MLE) to create a co-amorphous system by a solvent evaporation method. Phase diagrams of co-amorphous CAR-MLE, constructed from peak height in the Fourier-transform infrared (FTIR) spectra and the glass transition temperature (Tg) from differential scanning calorimetry (DSC) measurements, revealed that the optimal molar ratio of CAR to MLE was 2:1. The FTIR spectra indicated that the secondary amine-derived peak of CAR and the carboxy group-derived peak of MLE disappeared in the CAR:MLE (2:1) co-amorphous system. DSC measurements showed that the endothermic peaks associated with the melting of CAR and MLE disappeared and a Tg at 43 °C was apparent. Furthermore, the solubility of CAR tested using the shaking flask method for 24 h at 37 °C was 1.2 μg/mL, whereas that of the co-amorphous system was approximately three times higher, at 3.5 μg/mL. Finally, the stability was evaluated by powder- X-ray diffraction at 40 °C; no clear diffraction peaks originating from crystals were observed in the amorphous state until after approximately 3 months of storage. These results indicate that co-amorphization of CAR with MLE improved the solubility of CAR while maintaining its stability in an amorphous form.

Testing a Benchtop Wet-Milling Method for Preparing Nanoparticles and Suspensions as Hospital Formulations

In clinical practice, for elderly or pediatric patients who have difficulty swallowing, solid dosage forms such as tablets or capsules are crushed or unsealed, prepared as powder forms, and often administered as suspensions. However, because their dispersibility is poor, aggregation or precipitation occurs readily. Once precipitation and deposition happen, redispersion is difficult, which can limit patient and caretaker drug adherence. In this study, we attempted to prepare nanoparticles as a hospital formulation by a benchtop wet-milling method to obtain a suspension with high dispersibility. This is the first study to apply the wet-milling method to prepare the hospital formulation. We chose cefditoren pivoxil (CDTR-PI) as an experimental active pharmaceutical ingredient. CDTR-PI crystals were physically mixed with various water-soluble polymers such as polyvinylpyrrolidone, polyethylene oxide, hydroxypropyl cellulose, or hypromellose and wet-milled with a surface-active agent (sodium lauryl sulfate) under different conditions. The mean particle diameter of most of the samples was less than 200 nm. In FTIR spectra of ground samples, peak shifts suggesting inter- or intramolecular interactions between CDTR-PI and the other additive agents were not observed. Besides, the nanoparticle suspension had favorable dispersibility, as determined using a dispersion stability analyzer. Providing a suspension with high dispersibility makes dispense with the resuspension, the patient’s medication adherence would improve. These results show that suspended liquid formulations of active pharmaceutical ingredients could be obtained by the simple wet-milling method as hospital formulations.

Preparation of Fine Particles with Improved Solubility Using a Complex Fluidized-Bed Granulator Equipped with a Particle-Sizing Mechanism

A new type of fluidized-bed granulator equipped with a particle-sizing mechanism was used for the preparation of fine particles that improved the solubility of a poorly water-soluble drug substance. Cefteram pivoxyl (CEF) was selected as a model drug substance, and its solution with a hydrophilic polymer, hydroxypropyl cellulose (HPC-L), was sprayed on granulation grade lactose monohydrate (Lac). Three types of treated particles were prepared under different conditions focused on the spraying air pressure and the amount of HPC-L. When the amount of HPC-L was changed, the size of the obtained particles was similar. However, particle size distribution was dependent on the amount of HPC-L. Its distribution became more homogenous with greater amounts of HPC-L, but the particle size distribution obtained by decreasing the spraying air pressure was not acceptable. By processing CEF with HPC-L using a complex fluidized-bed granulator equipped with a particle-sizing mechanism, the dissolution ratio was elevated by approximately 40% compared to that of unprocessed CEF. Moreover, in the dissolution profile of treated CEF, the initial burst was suppressed, and nearly zero order release was observed up to approximately 60% in the dissolution profile. This technique may represent a method with which to design fine particles of approximately 100 µm in size with a narrow distribution, which can improve the solubility of a drug substance with low solubility.

Particle engineering in pharmaceutical solids processing: surface energy considerations

During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance.

Inverse gas chromatography applications: a review

Inverse gas chromatography (IGC) is a versatile, powerful, sensitive and relatively fast technique for characterizing the physicochemical properties of materials. Due to its applicability in determining surface properties of solids in any form such as films, fibres and powders of both crystalline and amorphous structures, IGC became a popular technique for surface characterization, used extensively soon after its development. One of the most appealing features of IGC that led to its popularity among analytical scientists in early years was its similarity in principle to analytical gas chromatography (GC). The main aspect which distinguishes IGC experiments from conventional GC is the role of mobile and stationary phases. Contrary to conventional GC, the material under investigation is placed in the chromatographic column and a known probe vapour is used to provide information on the surface. In this review, information concerning the history, instrumentation and applications is discussed. Examples of the many experiments developed for IGC method are selected and described. Materials that have been analysed include polymers, pharmaceuticals, minerals, surfactants, and nanomaterials. The properties that can be determined using the IGC technique include enthalpy and entropy of sorption, surface energy (dispersive and specific components), work of co/adhesion, miscibility and solubility parameters, surface heterogeneity, glass transition temperature, and specific surface area.

Aqueous solubility of crystalline and amorphous drugs: Challenges in measurement

Measurement of drug solubility is one of the key elements of active pharmaceutical ingredient (API) characterization during the drug discovery and development process. This report is a critical review of experimental methods reported in the literature for the measurement of aqueous solubility of amorphous, partially crystalline and crystalline organic compounds. A summary of high-throughput automated methods used in early drug discovery research is also provided in this report. This review summarizes the challenges that are encountered during solubility measurement and the complexities that are often overlooked. Even though there is an advantage in using the amorphous form of a drug due to its higher solubility, measurement of its solubility with useful accuracy is still a practical problem. Therefore, this review provides recommendations of preferred methods and precautions in using these methods to determine the aqueous solubility of amorphous and crystalline new molecular entities, with emphasis on the physico-chemical characterization of the solid state of the test substance.

Cefuroxime axetil solid dispersion with polyglycolized glycerides for improved stability and bioavailability

Objectives

Cefuroxime axetil (CA), a poorly soluble, broad spectrum cephalosporin ester prodrug, is hydrolysed by intestinal esterase prior to absorption, leading to poor and variable bioavailability. The objective was therefore to formulate a stable amorphous solid dispersion of the drug with enhanced solubility and stability against enzymatic degradation.

Methods

Spray drying was used to obtain a solid dispersion of CA with Gelucire 50/13 and Aerosil 200 (SDCAGA), and a solid dispersion of CA with polyvinyl pyrrolidone (SDCAP); amorphous CA (ACA) was obtained by spray drying CA alone. The formulations were characterized by differential scanning calorimetry, X-ray powder diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy studies, and compared for solubility, dissolution and bioavailability in rats.

Key findings

SDCAP and SDCAGA showed improved solubility and dissolution profiles owing to amorphization and formation of solid dispersions with hydrophilic carriers. The improved stability of amorphous CA in solid dispersions compared to ACA alone was attributed to hydrogen bonding interactions involving the amide of CA with the carbonyl of polyvinyl pyrrolidone in SDCAP, whereas in SDCAGA the interactions were at multiple sites involving the amide and carbonyl of CA with the carbonyl and hydroxyl of Gelucire 50/13. However, SDCAGA showed superior bioavailability compared to SDCAP, ACA and CA.

Conclusions

Improvement in physical stability of solid dispersions was attributed to hydrogen bonding, while improvement in bioavailability of SDCAGA compared to SDCAP, in spite of comparable solubility and dissolution profile, may be attributed to Gelucire, which utilizes intestinal esterase for lipolysis, protecting the prodrug from enzymatic degradation to its non-absorbable base form.

Investigation to find a suitable reference material for use as an inverse gas chromatography system suitability test

The purpose of this study was to find a suitable material for use as a system suitability test material for inverse gas chromatography (IGC). The purpose of a system check is to measure the variability of the instrument being used rather than the material being analysed. Having such a system check for IGC enables a basic GMP requirement to be met. IGC results can then be used in regulatory submissions to support other already established techniques for characterising pharmaceutical materials. Alpha-alumina was chosen because it is inorganic, stable at high temperatures, resistant to hydration and is already established as a system check material for surface area determination by nitrogen adsorption. Two columns (1 and 2) packed from the same reference sample jar of alpha-alumina and analysed under the same conditions yielded dispersive surface energies of 34.8+/-0.8 and 35.3+/-0.8 mJ/m(2), respectively, at 15% RH. Column 1 was analysed on a second IGC system, and gave a dispersive surface energy of 34.7+/-0.2 mJ/m(2). No significant change was evident after 7 months storage under laboratory ambient conditions. Analysis of material from a second reference sample jar of alpha-alumina produced results not noticeably different to those of the first, yielding a dispersive surface energy of 35.3+/-0.1 mJ/m(2). A change was seen to occur in the surface properties alpha-alumina when the humidity was varied, but the change appeared to be consistent across the two columns reported. Based upon the data in this experimental, alpha-alumina appears to be a suitable material for use as a system suitability test material for IGC.

Stabilization and Improved in Vivo Performance of Amorphous Etoricoxib using Gelucire 50/13

PURPOSE

Amorphous drugs have gained importance because of their advantageous biopharmaceutical properties; however, their stabilization remains a challenge. The purpose of this work was to stabilize the amorphous form of etoricoxib (ET) by using a low excipient/drug ratio to improve drug dissolution and thus bioavailability.

METHODS

The effect of Gelucire and polyvinylpyrrolidone (PVP) on stabilization and bioavailability of amorphous etoricoxib (AET) was studied. X-ray powder diffractometry, differential scanning calorimetry, and scanning electron microscopy were used to study the physical state of the drug. Dissolution studies were performed for melt granules of AET with Gelucire 50/13 (MG-AET) and solid dispersion with PVP (SDP) to differentiate dissolution performance. A stability study on samples was conducted for 3 months to evaluate the physical state of the drug and its dissolution in the formulation. The in vivo performance of the optimized and stable formulation of ET was evaluated in rat.

RESULTS

Dissolution of MG-AET was significantly improved as compared to AET and SDP. Both factors, amorphization of drug and melt granulation with lipid, seemed to be important for improving dissolution. Stability data revealed that MG-AET was significantly advantageous for AET stabilization, whereas PVP was not. The amount of Gelucire required for the stabilization of one part of AET was 0.5 part (by weight), whereas even 1.5 part (by weight) of PVP failed to elicit the same result. The superior in vivo performance of MG-AET has been attributed to the altered physiochemical properties of AET and the presence of lipid in the system.

CONCLUSION

Gelucire can stabilize AET and improve its biopharmaceutical performance at a low excipient/drug ratio and may provide a better alternative to conventional stabilizers such as PVP.