Improvement of Antialveolar Echinococcosis Efficacy of Albendazole by a Novel Nanocrystalline Formulation with Enhanced Oral Bioavailability

Metabolic mechanism and pharmacological study of albendazole in secondary hepatic alveolar echinococcosis (HAE) model rats

Albendazole (ABZ) is the primary treatment for alveolar echinococcosis (AE); however, its limited solubility impacts oral bioavailability, affecting therapeutic outcomes. In this study, various ABZ-solubilizing formulations, including albendazole crystal dispersion system (ABZ-CSD), albendazole hydrochloride-hydroxypropyl methylcellulose phthalate composite (TABZ-HCl-H), and albendazole hydroxyethyl sulfonate-hydroxypropyl methylcellulose phthalate composite (TABZ-HES-H), were developed and evaluated. Physicochemical properties as well as liver enzyme activity were analyzed and their pharmacodynamics in an anti-secondary hepatic alveolar echinococcosis (HAE) rat model were investigated. The formulations demonstrated improved solubility, exhibiting enhanced inhibitory effects on microcysts in HAE model rats compared to albendazole tablets. However, altered hepatic drug-metabolizing enzymes in HAE model rats led to increased ABZ levels and reduced ABZ-SO production, potentially elevating drug toxicity. These findings emphasize the importance of dose adjustments in patient administration, considering the impact of alveolar echinococcosis on rat hepatic drug metabolism.

Evaluation of microstructure, dissolution rate, and oral bioavailability of paclitaxel poloxamer 188 solid dispersion

Poor solubility is a major challenge for enhancing the oral bioavailability and clinical application of many drugs, including the broad-spectrum chemotherapy drug paclitaxel (PTX). A practical approach to improving the solubility of insoluble drugs is through the use of solid dispersion (SD). This study aimed to investigate the potential of the triblock copolymer, poloxamer 188 (P188), as a carrier for preparing solid dispersion of paclitaxel using spray drying technology. We systematically studied its microstructure, dissolution behavior in vitro, and pharmacokinetics. Our findings demonstrate that PTX exists in an amorphous state in copolymer composed of polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO) P188, with stronger miscibility with hydrophobic PPO segments. All three in vitro dissolution models revealed that the release rate of drugs in SD was significantly higher compared to that of physical mixtures (PM) as well as raw drugs. Furthermore, our pharmacokinetic results showed that the area under the curve(AUC) of PTX in SD was 6 times higher than that of active pharmaceutical ingredient(API), 4.5 times higher than PM, and the highest blood drug concentration (Cmax) reached 357.51 ± 125.54 (ng/mL), approximately 20 times higher than API. Overall, our findings demonstrate that the dissolution rate of amorphous PTX in SD significantly improves, effectively enhancing the oral bioavailability of PTX.

Influence Mechanism of Drug-Polymer Compatibility on Humidity Stability of Crystalline Solid Dispersion

This study investigates the influence of humidity on the dissolution behavior and microstructure of drugs in crystalline solid dispersions (CSDs). Using Bifonazole (BFZ) as a model drug, CSDs were prepared through spray drying with carriers such as Poloxamer 188 (P188), Poloxamer 407 (P407), and polyethylene glycol 8000 (PEG8000). The solubilization effect and mechanism were initially evaluated, followed by an examination of the impact of humidity (RH10%) on the dissolution behavior of CSDs. Furthermore, the influence of humidity on the microstructure of CSDs was investigated, and factors affecting the humidity stability of CSDs were summarized. Significant enhancements in the intrinsic dissolution rate (IDR) of BFZ in CSDs were observed due to changes in crystalline size and crystallinity, with the CSD-P188 system exhibiting the best performance. Following humidity treatment, the CSD-P407 system demonstrated the least change in the IDR of BFZ, indicating superior stability. The CSD-P407 system was followed by the CSD-P188 system, with the CSD-PEG8000 system exhibiting the least stability. Further analysis of the microstructure revealed that while humidity had negligible effects on the crystalline size and crystallinity of BFZ in CSDs, it had a significant impact on the distribution of BFZ on the CSD surface. This can be attributed to the water's potent plasticizing effect, which significantly alters the molecular mobility of BFZ. Additionally, the compatibility of the three polymers with BFZ differs, with CSD-P407 > CSD-P188 > CSD-PEG8000. Under the continuous influence of water, stronger compatibility leads to lower molecular mobility and more uniform drug distribution on the CSD surface. Enhancing the compatibility of drugs with polymers can effectively reduce the mobility of BFZ in CSDs, thereby mitigating changes caused by water and ultimately stabilizing the surface composition and dissolution behavior of drugs in CSDs.

Influence of Intermolecular Interactions on Crystallite Size in Crystalline Solid Dispersions

Crystalline solid dispersions (CSDs) represent a thermodynamically stable system capable of effectively reducing the crystallite size of drugs, thereby enhancing their solubility and bioavailability. This study uses flavonoid drugs with the same core structures but varying numbers of hydroxyl groups as model drugs and poloxamer 188 as a carrier to explore the intrinsic relationships between drug-polymer interactions, crystallite size, and in vitro dissolution behavior in CSDs. Initially, we investigate the interactions between flavonoid drugs and P188 by calculating Hansen solubility parameters, determination of Flory-Huggins interaction parameters, and other methods. Subsequently, we explore the crystallization kinetics of flavonoid drugs and P188 in CSD systems using polarized optical microscopy and powder X-ray diffraction. We monitor the domain size and crystallite size of flavonoids in CSDs through powder X-ray diffraction and a laser-particle-size analyzer. Finally, we validate the relationship between crystallite size and in vitro dissolution behavior through powder dissolution. The results demonstrate that, as the number of hydroxyl groups increases, the interactions between drugs and polymers become stronger, making drug crystallization in the CSD system less likely. Consequently, reductions in crystalline domain size and crystallite size become more pronounced, leading to a more significant enhancement in drug dissolution.

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.

Improvement of Antialveolar echinococcosis efficacy of novel Albendazole-Bile acids Derivatives with Enhanced Oral Bioavailability

Alveolar echinococcosis (AE) is a chronic and fatal infectious parasitic disease, which has not been well-researched. Current recommended therapies for AE by the World Health Organization include complete removal of the infected tissue followed by two years of albendazole (ABZ), administered orally, which is the only effective first-line anti-AE drug. Unfortunately, in most cases, complete resection of AE lesions is impossible, requiring ABZ administration for even longer periods. Only one-third of patients experienced complete remission or cure with such treatments, primarily due to ABZ's low solubility and low bioavailability. To improve ABZ bioavailability, albendazole bile acid derivative (ABZ-BA) has been designed and synthesized. Its structure was identified by mass spectrometry and nuclear magnetic resonance. Its physicochemical properties were evaluated by wide-angle X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and polarizing microscopy; it was compared with ABZ to assess its solubilization mechanism at the molecular level. To avoid the effects of bile acid on the efficacy of albendazole, the inhibitory effect of ABZ-BA on protoscolex (PSCs)s was observed in vitro. The inhibitory effect of ABZ-BA on PSCs was evaluated by survival rate, ultrastructural changes, and the expression of key cytokines during PSC apoptosis. The results showed that ABZ-BA with 4-amino-1-butanol as a linker was successfully prepared. Physicochemical characterization demonstrated that the molecular arrangement of ABZ-BA presents a short-range disordered amorphous state, which changes the drug morphology compared with crystalline ABZ. The equilibrium solubility of ABZ-BA was 4-fold higher than ABZ in vitro. ABZ-BA relative bioavailability (Frel) in Sprague-Dawley (SD) rats was 26-fold higher than ABZ in vivo. The inhibitory effect of ABZ-BA on PSCs was identical to that of ABZ, indicating that adding bile acid did not affect the efficacy of anti-echinococcosis. In the pharmacodynamics study, it was found that the ABZ-BA group had 2.7-fold greater than that of Albenda after 1 month of oral administration. The relative bioavailability of ABZ-BA is significantly better than ABZ due to the transformation of the physical state from a crystalline state to an amorphous state. Furthermore, sodium-dependent bile acid transporter (ASBT) expressed in the apical small intestine has a synergistic effect through the effective transport of bile acids. Therefore, we concluded that the NC formulation could potentially be developed to improve anti-AE drug therapy.

Nanocrystal Suspensions for Enhancing the Oral Absorption of Albendazole

Albendazole (ABZ), an effective benzimidazole antiparasitic drug is limited by its poor solubility and oral bioavailability. In order to overcome its disadvantages, ABZ nanocrystals were prepared using a novel bottom-up method based on acid-base neutralization recrystallization with high-speed mixing and dispersing. The cosolvent, stabilizer and preparation temperature were optimized using single factor tests. The physicochemical properties, solubility and pharmacokinetics of the optimal ABZ nanocrystals were evaluated. The high-performance liquid chromatography (HPLC), differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD) showed that ABZ had no structural and crystal phase change after nanocrystallization. The saturated solubility of ABZ nanocrystals in different solvents was increased by 2.2-118 fold. The oral bioavailability of the total active ingredients (ABZ and its metabolites of albendazole sulfoxide (ABZSO) and albendazole sulfone (ABZSO2)) of the nanocrystals in rats was enhanced by 1.40 times compared to the native ABZ. These results suggest that nanocrystals might be a promising way to enhance the solubility and oral bioavailability of ABZ and other insoluble drugs.

Water-Resistant Drug-Polymer Interaction Contributes to the Formation of Nano-Species during the Dissolution of Felodipine Amorphous Solid Dispersions

Drug-polymer interactions are of great importance in amorphous solid dispersion (ASD) formulation for both dissolution performance and physical stability considerations. In this work, three felodipine ASD systems with drug loading ranging from 5 to 20% were prepared using PVP, PVP-VA, or HPMC-AS as the polymer matrix. The amorphization and homogeneity were confirmed by differential scanning calorimetry and powder X-ray diffraction. The intrinsic dissolution behavior of these ASDs was studied in 0.05 M HCl and phosphate-buffered saline (PBS) (pH 6.5). In 0.05 M HCl, PVP-VA ASDs with low drug loading (<15%) showed rapid dissolution accompanied with nano-species generation, while in the PVP system, rapid dissolution and nano-species generation were observed only when drug loading was less than 10%, and HPMC-AS ASDs always released slowly with no nano-species formation. In PBS, PVP-VA ASDs with drug loading less than 10% showed rapid dissolution accompanied with nano-species generation, while for PVP ASDs, rapid dissolution and nano-species generation were observed only when drug loading was 5%. However, 20% drug loading HPMC-AS ASDs exhibited rapid dissolution of felodipine and nano-species generation. When the drug loading was above the transition point of PVP-VA ASDs and PVP ASDs, the release rate was significantly lowered, and no nano-species was generated. To understand this phenomenon, drug-polymer interactions were studied using the melting point depression method and the Flory-Huggins model fitting. The Flory-Huggins interaction parameters (χ) for felodipine/HPMC-AS, felodipine/PVP, and felodipine/PVP-VA were determined to be 0.62 ± 0.07, -0.55 ± 0.20, and -1.02 ± 0.21, respectively, indicating the existence of the strongest attractive molecular interaction between felodipine and PVP-VA, followed by felodipine/PVP, but not in felodipine/HPMC-AS. Furthermore, dynamic vapor sorption further revealed that the molecular interactions between felodipine and PVP or PVP-VA were resistant to water. We concluded that water-resistant drug-polymer interactions in felodipine/polymer systems were responsible for the formation of nano-species, which further facilitated the rapid initial drug dissolution.

Improvement of the Bioavailability and Anti-hepatic Alveolar Echinococcosis Effect of Albendazole-Isethionate/Hypromellose Acetate Succinate (HPMC-AS) Complex

Maximizing the pharmacodynamics of albendazole (ABZ), which is used to treat echinococcoses, is essential for the long-term treatment of echinococcosis patients. ABZ is a weak base whose solubility depends on the pH value of the solvent. After it has been orally administered, its solubility drops sharply from when it is in gastric juices (pH 1.4) to when it is in intestinal juices (pH 6.5) and is subsequently absorbed in the ileum and jejunum. This results in low solubility and poor bioavailability of the drug. In this study, we developed an orally administered albendazole-isethionate (ABZ-HES)/hypromellose acetate succinate (HPMC-AS) complex tablet (T_ABZ-HES-H) with improved solubility and bioavailability. Previous studies demonstrated that ABZ-HES has a higher intrinsic dissolution rate under pH 1.4 than the ABZ free base used in the commercial product Albenda and that HPMC-AS can effectively inhibit ABZ crystallization, which could be due to the hydrophobic interaction between ABZ and HPMC-AS in an aqueous environment. In this study, the dissolution behavior of T_ABZ-HES-H in vitro was studied by the two-step pH conversion method. Our results demonstrated that the oral bioavailability of T_ABZ-HES-H was approximately 2.6 times higher than that of ABZ. More importantly, in the rat model of secondary hepatic alveolar echinococcosis, the anti-hepatic alveolar echinococcosis effect of T_ABZ-HES-H was 3.4 times higher than that of a commercial product. The improved preparation with salt and polymer has proven to be a feasible method of improving the oral bioavailability and pharmacodynamics of ABZ.

Albendazole solid dispersions against alveolar echinococcosis: a pharmacotechnical strategy to improve the efficacy of the drug

Alveolar echinococcosis is a neglected parasitic zoonosis caused by Echinococcus multilocularis. The pharmacological treatment is based on albendazole (ABZ). However, the low water solubility of the drug produces a limited dissolution rate, with the consequent failure in the treatment of the disease. Solid dispersions are a successful pharmacotechnical strategy to improve the dissolution profile of poorly water-soluble drugs. The aim of this work was to determine the in vivo efficacy of ABZ solid dispersions using poloxamer 407 as a carrier (ABZ:P407 solid dispersions (SDs)) in the murine intraperitoneal infection model for secondary alveolar echinococcosis. In the chemoprophylactic efficacy study, the ABZ suspension, the ABZ:P407 SDs and the physical mixture of ABZ and poloxamer 407 showed a tendency to decrease the development of murine cysts, causing damage to the germinal layer. In the clinical efficacy study, the ABZ:P407 SDs produced a significant decrease in the weight of murine cysts. In addition, the SDs produced extensive damage to the germinal layer. The increase in the efficacy of ABZ could be due to the improvement of water solubility and wettability of the drug due to the surfactant nature of poloxamer 407. In conclusion, this study is the basis for further research. This pharmacotechnical strategy might in the future offer novel treatment alternatives for human alveolar echinococcosis.

Enhanced Oral Bioavailability and Anti-Echinococcosis Efficacy of Albendazole Achieved by Optimizing the "Spring" and "Parachute"

Maximizing the pharmacological efficacy of albendazole (ABZ), an anti-echinococcosis drug, is essential in the long-term treatment of patients with echinococcosis. As a weakly alkaline drug, ABZ has a pH-dependent solubility that decreases dramatically from gastric fluid (pH 1.4) to intestinal fluid (pH 6.5), where it is absorbed. In this study, we endeavored to develop an optimized tablet formulation of ABZ to improve its dissolution and oral bioavailability from two aspects: a faster initial dissolution in the gastric pH condition (i.e., the "spring") and a more prolonged drug supersaturation in the intestinal pH condition (i.e., the "parachute"). To achieve this goal, ABZ-HCl salt was selected first, which demonstrated a higher intrinsic dissolution rate under pH 1.4 compared with the ABZ free base that is used in the commercial product Albenda. Second, by comparing the ABZ supersaturation kinetics under pH 6.5 in the presence of various polymers including poly(vinylpyrrolidone) (PVP), PVP/VA, hydroxypropyl methylcellulose (HPMC), and HPMC acetate succinate (HPMC-AS), HPMC-AS was found to be the most effective crystallization inhibitor for ABZ, likely due to the hydrophobic interaction between ABZ and HPMC-AS in an aqueous environment. The newly designed tablet formulation containing ABZ-HCl and HPMC-AS showed ∼3 times higher oral bioavailability compared with that of Albenda in Beagle dogs. More significantly, the anti-echinococcosis efficacy of the improved formulation was 2.4 times higher than that of Albenda in a secondary hepatic alveolar echinococcosis Sprague-Dawley rat model. The strategy of simultaneously improving the spring and parachute of an oral formulation of ABZ, by using a highly soluble salt and an effective polymeric crystallization inhibitor, was once again proven to be a viable and readily translatable approach to optimize the unsatisfactory oral medicines due to solubility and bioavailability limitations.