CLSM as quantitative method to determine the size of drug crystals in a solid dispersion

The Use of Global Sensitivity Analysis to Assess the Oral Absorption of Weakly Basic Compounds: A Case Example of Dipyridamole

OBJECTIVE

To utilize the global system analysis (GSA) in oral absorption modeling to gain a deeper understanding of system behavior, improve model accuracy, and make informed decisions during drug development.

METHODS

GSA was utilized to give insight into which drug substance (DS), drug product (DP), and/or physiological parameter would have an impact on peak plasma concentration (Cmax) and area under the curve (AUC) of dipyridamole as a model weakly basic compound. GSA guided the design of in vitro experiments and oral absorption risk assessment using FormulatedProducts v2202.1.0. The solubility and precipitation profiles of dipyridamole in different bile salt concentrations were measured. The results were then used to build a mechanistic oral absorption model.

RESULTS

GSA warranted further investigation into the precipitation kinetics and its link to the levels of bile salt concentrations. Mechanistic modeling studies demonstrated that a precipitation-integrated modeling approach appropriately predicted the mean plasma profiles, Cmax, and AUC from the clinical studies.

CONCLUSIONS

This work shows the value of GSA utilization in early development to guide in vitro experimentation and build more confidence in identifying the critical parameters for the mathematical models.

Study on the regulation mechanism of effective glass transition temperature on the crystallization of crystalline solid dispersion

The focus of this investigation was to determine the mechanism of effective glass transition temperature (TgE) on the crystallization behavior and microstructure of drugs in crystalline solid dispersion (CSD). CSDs were prepared by rotary evaporation using ketoconazole (KET) as a model drug and the triblock copolymer poloxamer 188 as a carrier. The pharmaceutical properties of CSDs, such as crystallite size, crystallization kinetics, and dissolution behavior, were investigated to provide a foundation for studying the crystallization behavior and the microstructure of drugs in CSDs. According to classical nucleation theory, the relationship of treatment temperature-drug crystallite size-TgE of CSD was investigated. Voriconazole, a compound that is structurally similar to KET but with different physicochemical properties, was used to verify the conclusions. The dissolution behavior of KET was significantly enhanced compared to the raw drug due to smaller crystallite size. Crystallization kinetic studies revealed a two-step crystallization mechanism for KET-P188-CSD, in which P188 crystallized first and KET crystallized later. When the treatment temperature was near TgE, the drug crystallite size was smaller and more numerous, which suggests nucleation and slow growth. With the increase of temperature, the drug changed from nucleation to growth, and the number of crystallites decreased and the size of the drug increased. This result suggests it is possible to prepare CSDs with higher drug loading and smaller crystallite size by adjusting the treatment temperature and TgE, so as to maximize the drug dissolution rate. The VOR-P188-CSD maintained a relationship between treatment temperature, drug crystallite size, and TgE. The findings of our study demonstrate that TgE and the treatment temperature can be used to regulate the drug crystallite size and improve the drug solubility and dissolution rate.

Multi-walled carbon nanotube-based systems for improving the controlled release of insoluble drug dipyridamole

Applicability of multi-walled carbon nanotubes (MWCNTs) in loading dipyridamole (DDM), a poorly soluble drug, was evaluated. Additionally, the effect of drug-loading efficiency on the release behavior of the MWCNT-DDM system was also investigated. DDM as a model drug was incorporated into MWCNTs with different drug-loading rates (10, 25 and 50%) using the solvent deposition method. The MWCNT-DDM system was successfully established and characterized using common solid-state characterization methods. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption analysis and Fourier transform-infrared (FT-IR) spectroscopy were carried out to observe the progress of drug loading. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to systematically assess the crystalline state of the DDM after being loaded into the MWCNTs. Improvements in dissolution rate were evaluated by the dissolution test. The results revealed that with the increase of drug loading, the form of DDM in the MWCNTs changed from amorphous to crystalline state. Also, the release rate of DDM decreased upon increasing the drug-loading rate of carriers. In conclusion, MWCNTs are proven to be promising carriers for loading DDM.