Amorphous Solid Dispersions of Glycyrrhetinic Acid: Using Soluplus, PVP, and PVPVA as the Polymer Matrix to Enhance Solubility, Bioavailability, and Stability.

Glycyrrhetinic acid (GA) possesses various pharmacological effects, including anti-inflammatory, anti-tumor, and anti-viral properties. However, its clinical application is limited by poor solubility and low oral bioavailability. Polymers play a crucial role in pharmaceutical formulations, particularly as matrices in excipients to enhance the solubility, bioavailability, and stability of active pharmaceutical ingredients. The amorphous solid dispersions (ASDs) of GA were prepared with three different polymers (i.e., GA-S-ASD, GA-VA64-ASD, and GA-K30-ASD). The ASDs were characterized by differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR spectroscopy), molecular docking, and contact angle measurement. Pharmacokinetics were evaluated in Beagle dogs, and long-term stability was examined. The solubility of GA increased with the rising weight of the polymer, and the optimal drug-to-carrier ratio was 1:5. In all ASDs, GA was amorphous, thus suggesting that a hydrogen bonding must have formed between GA and the polymers. The molecular docking showed that the binding energy was the highest and the hydrogen bonding was the strongest between GA and Soluplus. The dissolution of the ASDs was primarily driven by carrier-controlled dissolution, and there was minor influence from diffusion-limited release in the case of GA-S-ASD. The three ASDs significantly improved the bioavailability of GA. However, only GA-S-ASD passed the accelerated stability test. In the case of GA-VA64-ASD and GA-K30-ASD, due to serious moisture absorption, the originally fluffy ASDs became gels, and recrystallization occurred. Overall, GA-S-ASD presents promising potential for pharmaceutical applications due to its superior solubility, bioavailability, and stability.