Amorphization and modified release of ibuprofen by post-synthetic and solvent-free loading into tailored silica aerogels

Promising active pharmaceutical ingredients (APIs) often exhibit poor aqueous solubility and thus a low bioavailability that substantially limits their pharmaceutical application. Hence, efficient formulations are required for an effective translation into highly efficient drug products. One strategy is the preservation of an amorphous state of the API within a carrier matrix, which leads to enhanced dissolution. In this work, mesoporous silica aerogels (SA) were utilized as a carrier matrix for the amorphization of the poorly water-soluble model drug ibuprofen. Loading of tailored SA was performed post-synthetically and solvent-free, either by co-milling or via the melting method. Thorough analyses of these processes demonstrated the influence of macrostructural changes during the drying and grinding process on the microstructural properties of the SA. Furthermore, interfacial SA-drug interaction properties were selectively tuned by attaching terminal hydrophilic amino- or hydrophobic methyl groups to the surface of the gel. We demonstrate that not only the chemical surface properties of the SA, but also formulation-related parameters, such as the carrier-to-drug ratio, as well as process-related parameters, such as the drug loading method, decisively influence the ibuprofen adsorption efficiency. In addition, the drug-loaded SA formulations exhibited a remarkable physical stability over a period of 6 months. Furthermore, the release behavior is shown to change considerably with different surface properties of the SA matrix. Hence, the reported results demonstrate that utilizing specifically processed and modified SA offers a compelling technique for enhancement of the bioavailability of poorly-water soluble APIs and a versatile adjustment of their release profile.

Disintegration of solid foods in human stomach

Knowledge of the disintegration of solid foods in human stomach is essential to assess the bioavailability of nutrients in the gastrointestinal (GI) tract. A comprehensive review of food gastric digestion, focusing on disintegration of solid foods, is presented. Most of the research reviewed in this paper is contained in the medical, pharmaceutical, food, and nutritional literature. Stomach physiology is briefly introduced, including composition and rheological properties of gastric contents, stomach wall motility in fed/fasted states, and hydrodynamic and mechanical forces that act on the ingested food. In vivo and in vitro methods used for studying food and drug digestion in GI are summarized. Stomach emptying rate, which controls the rate of absorption of nutrients, is highly related to the disintegration of foods. This topic is highlighted with focus on the important mechanisms and the influence of chemical and physical properties of foods. Future research in this area is identified to increase our fundamental understanding of the food digestion process in the stomach as related to the food composition, material properties such as texture and microstructure, and chemical characteristics. This information is necessary to develop new guidelines for seeking innovative processing methods to manufacture foods specifically targeted for health.

Cyclodextrin Multicomponent Complexation and Controlled Release Delivery Strategies to Optimize the Oral Bioavailability of Vinpocetine

In the present work, to maintain a suitable blood level of vinpocetine (VP) for a long period of time, VP-cyclodextrin-tartaric acid multicomponent complexes were prepared and formulated in hydroxypropylmethylcellulose matrix tablets. In vitro and in vivo performances of these formulations were investigated over a VP immediate release dosage form. Solubility studies were performed to evaluate the drug pH solubilization profile and to assess the effect of multicomponent complexation on VP solubility. The drug release process was investigated using United States Pharmacopeia apparatus 3 and a comparative oral pharmacokinetic study was subsequently undertaken in rabbits. Solubility studies denoted the pH-solubility dependence of VP and solubility improvement attained by complexation. Dissolution results showed controlled and almost complete release behavior of VP over a 12-h period from complex hydroxypropylmethylcellulose-based formulations. A clear difference between the pharmacokinetic patterns of VP immediate release and VP complex-based formulations was revealed. The area under the plasma concentration-time curve after oral administration of complex-based formulations was 2.1-2.9 times higher than that for VP immediate release formulation. Furthermore, significant differences found for mean residence time, elimination half-life, and elimination rate constant values corroborated prolonged release of VP from complex-based formulations. These results suggest that the oral bioavailability of VP was significantly improved by both multicomponent complexation and controlled release delivery strategies.

Dissolution rate enhancement by adsorption of poorly soluble drugs on hydrophilic silica aerogels

The aim of this work is to evaluate the feasibility of hydrophilic silica aerogels as drug carriers and to investigate the influence of the aerogels properties on the release rate of poorly water-soluble drugs. Hydrophilic silica aerogels of different densities were loaded with two model drugs, ketoprofen and griseofulvin, by adsorption from their solution in supercritical CO2. It is demonstrated that up to 30 wt% of ketoprofen and 5.4 wt% of griseofulvin can be deposited on hydrophilic aerogels through physical adsorption. The obtained drug-aerogel formulations were characterized by IR- and UV-spectroscopy, X-ray diffraction and scanning electron microscopy. Release kinetics of both drugs were studied in vitro. The release rate of ketoprofen from the drug-aerogel formulation is much faster than that of the corresponding crystalline drugs. The release rate of ketoprofen increases in 500% and that of griseofulvin in 450%, respectively. The reasons for the release enhancement are the enlarged specific surface area of drugs by adsorption on aerogels compared to their crystalline form and the immediate collapse of aerogel network in aqueous media. The dissolution rate of poorly water soluble drugs can be significantly enhanced by adsorption on highly porous hydrophilic silica aerogels.

In vitro controlled release of vinpocetine-cyclodextrin-tartaric acid multicomponent complexes from HPMC swellable tablets

The objective of this study was to investigate the effect of multicomponent complexation (MCC) of vinpocetine (VP), a poorly soluble base-type drug, with beta-cyclodextrin (betaCD), sulfobutylether beta-cyclodextrin (SBEbetaCD), tartaric acid (TA), polyvinylpyrrolidone (PVP) and hydroxypropylmethylcellulose (HPMC), on the design of controlled release hydrophilic HPMC tablets and to evaluate their in vitro release profiles by a pH gradient method. Multicomponent complexation led to enhanced dissolution properties of VP both in simulated gastric and intestinal fluids, and became possible the development of HPMC tablet formulations with more independent pH dissolution profiles. Drug release process was investigated experimentally using USP apparatus 3 and by means of model-independent parameters. Responses studied included similarity of dissolution profiles, time for 60% of the drug to dissolve (T(60%)), percent of VP released after 7 h (PD(7 h)) and the dissolution efficiency parameter at 12 h (DE(12 h)). Influence of multicomponent complexation was proved to increase the release of VP from HPMC tablets and superior PD(7 h) and DE(12 h) values were obtained in formulations containing VP-CD-TA complexes. Results supported the use of HPMC matrices to provide a useful tool in retarding the release of VP and that dissolution characteristics of the drug may be modulated by multicomponent complexation in these delivery systems, suggesting an improvement on VP bioavailability.

Abnormal dissolutions of chlorpromazine hydrochloride tablets in water by paddle method under a high agitation condition

All sugar-coated tablets of chlorpromazine hydrochloride except for those produced by one manufacture showed concave dissolution profiles in water by paddle method at 100 rpm but not at 50 rpm. The study was undertaken to clarify the agitation-dependent abnormal dissolutions. The strange dissolutions were also observed in water at different ionic strengths but not in buffer solutions of pH 1.2, 4.0 and 6.8. When monitored, the pH's of water in dissolution vessels for the abnormal tablets increased with time at 100 rpm and some of them exceeded pH 8 but did not at 50 rpm. The solubility of chlorpromazine hydrochloride decreased with the increase of pH which was too low to dissolve the whole amount of drug contained in a tablet at pH 8. The elevation of pH seemed to be mainly brought about by dissolution of calcium carbonate popularly used for sugar-coated tablets, because larger amount of calcium ion was dissolved out from the abnormal tablets at 100 rpm than from a normal tablet and from them at 50 rpm. These findings indicate that the concave dissolution profiles should be caused by the decrease of drug solubility with increase in pH of water, probably because of dissolution of calcium carbonate. We should pay attention to the change in pH of water which may differ depending on the agitation speed of dissolution tests.

Optimization of dissolution test precision for a ketoprofen oral extended-release product

An example of application of experimental design methodologies to the set up of dissolution test conditions for a new ketoprofen oral extended-release dosage form is presented. The aim of the work was to find the best experimental conditions, using a USP apparatus 2 (paddle), for maximizing the method precision as degree of repeatability. The considered factors mainly influencing the dissolution test results were pH and volume of dissolution medium, and paddle stirring speed. Two distinct 4-run Plackett-Burman designs were carried out: one at gastric and the other at intestinal pH values. Each run was performed in triplicate in order to calculate the standard deviations of the drug dissolution efficiency at 60 and 120 min, selected as responses to be minimized. Optimum conditions to carry out the dissolution test were: 900 ml volume of dissolution medium and 70 rpm paddle stirring speed for both environments and pH 1 and 5.5, for the gastric and intestinal environment, respectively.

An evaluation of fit factors and dissolution efficiency for the comparison of in vitro dissolution profiles

Dissolution efficiency (D.E.), the area under a dissolution curve between defined time points, and the fit factors (f1 and f2) have been compared for the characterisation of dissolution profiles, using data from three batches of a product in nine different packs stored under two conditions. The factors f1 and f2 offer ease of calculation and a simple measure of similarity between pairs of dissolution profiles. This is well suited to the qualitative determination of 'similarity' as required by the FDA's SUPAC Guide. However, they do not provide information on individual batches, including their consistency. In contrast, D.E. does provide such information is well-suited to making quantitative comparisons amongst batches. Because D.E. has a simple physical meaning, it is easier to interpret D.E. data then corresponding f1 and f2 results. The confidence limits in D.E. values provide a useful measure of the variability in batch dissolution and allow the statistical significance of difference in D.E. between pairs of batches to be determined. Both of the above measures lead to the same conclusions regarding the similarity in protective power amongst the nine packs under test and to the value of added desiccant in maintaining the dissolution profile of the product when stored under high humidity conditions. It is concluded that D.E. offers a suitable alternative to the single point dissolution measurement for QC of immediate release products.