Synergistic effect of polyethylene glycol and superdisintegrant on dissolution rate enhancement of simvastatin in pellet formulation

Stability-Enhanced Ternary Solid Dispersions of Glyburide: Effect of Preparation Method on Physicochemical Properties

Introduction

Limited aqueous solubility and subsequent poor absorption and low bioavailability are the main challenges in oral drug delivery. Solid dispersion is a widely used formulation strategy to overcome this problem. Despite their efficiency, drug crystallization tendency and poor physical stability limited their commercial use. To overcome this defect, ternary solid dispersions of glyburide: sodium lauryl sulfate (SLS) and polyethylene glycol 4000 (PEG), were developed using the fusion (F) and solvent evaporation (SE) techniques and subsequently evaluated and compared.

Materials and Methods

Physicochemical and dissolution properties of the prepared ternary solid dispersions were evaluated using differential scanning calorimetry (DSC), infrared spectroscopy (FTIR), and dissolution test. Flow properties were also assessed using Carr's index and Hausner's ratio. The physical stability of the formulations was evaluated initially and after 12 months by comparing dissolution properties.

Results

Formulations prepared by both methods similarly showed significant improvements in dissolution efficiency and mean dissolution time compared to the pure drug. However, formulations that were prepared by SE showed a greater dissolution rate during the initial phase of dissolution. Also, after a 12-month follow-up, no significant change was observed in the mentioned parameters. The results of the infrared spectroscopy indicated that there was no chemical interaction between the drug and the polymer. The absence of endotherms related to the pure drug from thermograms of the prepared formulations could be indicative of reduced crystallinity or the gradual dissolving of the drug in the molten polymer. Moreover, formulations prepared by the SE technique revealed superior flowability and compressibility in comparison with the pure drug and physical mixture (ANOVA, P  <  0.05).

Conclusion

Efficient ternary solid dispersions of glyburide were successfully prepared by F and SE methods. Solid dispersions prepared by SE, in addition to increasing the dissolution properties and the possibility of improving the bioavailability of the drug, showed acceptable long-term physical stability with remarkably improved flowability and compressibility features.

Solid Dispersion Pellets: An Efficient Pharmaceutical Approach to Enrich the Solubility and Dissolution Rate of Deferasirox

Deferasirox (DFX) is an oral iron-chelating agent and classified into class II of the Biopharmaceutics Classification System. Low bioavailability of the drug due to insufficient solubility in physiological fluids is the main drawback of DFX. The idea of the current study was to explore the potential of solid dispersion (SD) as an effective method to improve the dissolution rate of DFX in pellets. The SDs were made by the solvent evaporation technique using polyethylene glycol 4000 (PEG 4000) and polyvinylpyrrolidone K25 with different drug-to-carrier ratios. Then, the dispersion was milled and mixed with other components and the mixture layered on sugar-based cores by pan coating technique. The pellets were evaluated in terms of size distribution, morphology (SEM), and dissolution behaviour. Drug-polymer interactions were studied using differential scanning calorimetry (DSC), X-ray diffraction study (XRD), and Fourier transformation infrared (FTIR) spectroscopy. The pellets coated with SD showed a remarkable rise in the solubility of DFX than that of free drug-loaded pellets. The dispersion with PVP K25 showed a faster dissolution rate as compared to other mixtures. The DSC and XRD analysis indicated that the drug was in the amorphous state when dispersed in the polymer. The FTIR studies demonstrated any ruled out interaction between drug and polymer. The SEM showed smoothness on the surface of the pellets. It is resolved that the SD method considerably enriched the dissolution rate of DFX in pellets, which can also be utilized for other poorly water-soluble drugs.

Experimental, Thermodynamic, and Molecular Modeling Evaluation of Amorphous Simvastatin-Poly(vinylpyrrolidone) Solid Dispersions

A crucial step for the selection of proper amorphous solid dispersion (ASD) matrix carriers is the in-depth assessment of drug/polymer physicochemical properties. In this context, the present study extends the work of previously published attempts by evaluating the formation of simvastatin (SIM)-poly(vinylpyrrolidone) (PVP) ASDs with the aid of thermodynamic and molecular modeling. Specifically, the implementation of both Flory-Huggins lattice theory and molecular dynamics (MD) simulations was able to predict the miscibility between the two components (a finding that was experimentally verified via differential scanning calorimetry (DSC) and hot stage polarized microscopy), while a complete temperature-concentration phase-transition profile was constructed, leading to the identification of the thermodynamically metastable and unstable ASD zones. Furthermore, as in the case of previously published reports, the analysis of the ASDs via Fourier transform infrared spectroscopy did not clarify the type and extent of observed molecular interactions. Hence, in the present study, a computer-based MD simulation model was developed for the first time in order to gain an insight into the properties of the observed interactions. MD amorphous assemblies of SIM, PVP, and their mixtures were initially developed, and the calculated glass transition temperatures were in close agreement with experimentally obtained results, indicating that the developed models could be considered as realistic representations of the actual systems. Furthermore, molecular interactions evaluation via radial distribution function and radius of gyration analysis revealed that increasing SIM content results in a significant PVP chain shrinkage, which eventually leads to SIM-SIM amorphous intermolecular interactions, leading to the formation of amorphous drug zones. Finally, MD-based results were experimentally verified via DSC.