Enhanced solubility and intestinal absorption of candesartan cilexetil solid dispersions using everted rat intestinal sacs

Supersaturated Drug Delivery System of Oxyberberine Based on Cyclodextrin Nanoaggregates: Preparation, Characterization, and in vivo Application

Propose

Oxyberberine (OBB), one of the main metabolites of berberine derived from intestinal and erythrocyte metabolism, exhibits appreciable anti-hyperuricemic activity. However, the low water solubility and poor plasma concentration-effect relationship of OBB hamper its development and utilization. Therefore, an OBB-hydroxypropyl-β-cyclodextrin (HP-β-CD) supersaturated drug delivery system (SDDS) was prepared and characterized in this work.

Methods

OBB-HP-β-CD SDDS was prepared using the ultrasonic-solvent evaporation method and characterized. Additionally, the in vitro and in vivo release experiments were conducted to assess the release kinetics of OBB-HP-β-CD SDDS. Subsequently, the therapeutic efficacy of OBB-HP-β-CD SDDS on hyperuricemia (HUA) was investigated by means of histopathological examination and evaluation of relevant biomarkers.

Results

The results of FT-IR, DSC, PXRD, NMR and molecular modeling showed that the crystallized form of OBB was transformed into an amorphous OBB-HP-β-CD complex. Dynamic light scattering indicated that this system was relatively stable and maintained by formation of nanoaggregates with an average diameter of 23 nm. The dissolution rate of OBB-HP-β-CD SDDS was about 5 times higher than that of OBB raw material. Furthermore, the AUC0-t of OBB-HP-β-CD SDDS (10.882 μg/mL*h) was significantly higher than that of the raw OBB counterpart (0.701 μg/mL*h). The oral relative bioavailability of OBB-HP-β-CD SDDS was also enhanced by 16 times compared to that of the raw material. Finally, in vivo pharmacodynamic assay showed the anti-hyperuricemic potency of OBB-HP-β-CD SDDS was approximately 5-10 times higher than that of OBB raw material.

Conclusion

Based on our findings above, OBB-HP-β-CD SDDS proved to be an excellent drug delivery system for increasing the solubility, dissolution, bioavailability, and anti-hyperuricemic potency of OBB.

Dissolution enhancement of Gefitinib by solid dispersion and complexation with β-cyclodextrins: In vitro testing, cytotoxic activity, and tablet formulation

Cancer is the leading cause of mortality worldwide. In patients with metastatic non-small cell lung cancer, epidermal growth factor receptor (EGFR) is often overexpressed. Gefitinib (GEF), an inhibitor of EGFR, is approved for the treatment of patients with metastatic non-small cell lung cancer (NSCLC). However, the low solubility and dissolution of GEF limits its bioavailability. Numerous methods, including solid dispersion (SD) and complexation, have been reported to enhance the dissolution of poorly soluble drugs. In this study, GEF complexes were prepared using methyl-β-cyclodextrin (MβCD) and hydroxypropyl-β-cyclodextrin (HPβCD) in two molar ratios (1:1 and 1:2), furthermore, GEF SDs were prepared using polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and poloxamer-188(PXM) in three different ratios (1:2, 1:4 and 1:6 w/w). Dissolution studies were conducted on the prepared formulations. Dissolution results showed a 1.22-2.17-fold enhancement in drug dissolution after one hour compared to untreated GEF. Two formulations that showed higher dissolution enhancement were subsequently evaluated for in-vitro cytotoxicity and were formulated into tablets. The selected PVP-GEF (1:4 w/w) and MβCD-GEF (1:1M) formulas displayed improved cytotoxicity compared to untreated GEF. The IC50 values of the PVP-GEF and MβCD-GEF were 4.33 ± 0.66 and 4.84 ± 0.38 µM, respectively which are significantly lower (p < 0.05) than free GEF. In addition, the formulated tablets exhibited enhanced dissolution compared to pure GEF tablets. PVP-GEF SD tablets released (35.1 %±0.4) of GEF after one hour, while GEF-MβCD tablets released (42.2 % ± 0.7) after one hour. In the meantime, tablets containing pure GEF showed only 15 % ± 0.5 release at the same time. The findings of this study offer valuable insights for optimizing the dissolution and hence therapeutic capabilities of GEF while mitigating its limitations.

Solusomes (novel soluplus® enriched nano-vesicular carriers) for improving the oral bioavailability of Candesartan cilexetil

Candesartan cilexetil (CAN) is administered for treating hypertension and heart failure. CAN suffers poor oral bioavailability, owing to limited aqueous solubility, and first-pass metabolism. Solusomes (novel Soluplus® enriched nano-vesicular carriers) combine the merits of Soluplus®, and the traditional liposomes. They were explored to increase CAN solubility, allow a high drug release rate, and improve the oral drug bioavailability. Solusomes were developed via thin film hydration technique utilizing lipid (phosphatidylcholine; PC) and polymeric solubilizer (Soluplus®; Solu). S6 system comprising PC (0.1% w/v), CAN and Soluplus® (at 1:5 ratio; w/w), following a 5 min sonication period, was the optimum one with respect to drug entrapment efficiency (83.5 ± 2.6%), drug loading (11.9 ± 0.3%), particle size and shape (377.2 ± 12.1 nm, spherical), zeta-potential (-19.6 ± 2.1 mV), saturated drug solubility (32.09 ± 0.71 µg/mL), drug released % after 1 h (68 ± 0.9%), and stability. Significantly higher Cmax (969.12 ± 46.3 ng/mL), shorter median Tmax (1h), and improved relative bioavailability (≈ 6.8 folds) in rabbits could evidence the potential of S6 system in enhancing oral CAN bioavailability. S6 solusomes act as dual platform to improve the oral drug bioavailability and maintain effective drug concentration for a prolonged period.

Mixed Pluronic/lecithin micelles formulation for oral bioavailability of candesartan cilexetil drug: in vitro characterization and in vivo pharmacokinetic investigations

OBJECTIVE

This study aimed to develop a mixed polymeric micelle formulation incorporating candesartan cilexetil (CAND) drug to enhance its oral bioavailability for the better treatment of hypertension.

METHODS

A Box-Behnken design was utilized to optimize the CAND-incorporated mixed polymeric micelles formulation (CAND-PFLC) consisting of Pluronics (P123 and F68) and lecithin (LC). The optimized CAND-PFLC micelles formulation was characterized for size, shape, zeta potential, polydispersity index (PDI), and entrapment efficiency (%EE). An in vitro release study, ex vivo permeability investigation, and an in vivo pharmacokinetic analysis were carried out to evaluate the performance of the formulation.

RESULTS

The optimized CAND-PFLC micelles formulation demonstrated a spherical shape, a particle size of 44 ± 2.03 nm, a zeta potential of -7.07 ± 1.39 mV, a PDI of 0.326 ± 0.06, and an entrapment efficiency of 87 ± 3.12%. The formulation exhibited excellent compatibility, better stability, and a noncrystalline nature. An in vitro release study revealed a faster drug release of 7.98% at gastric pH in 2 hrs and 94.45% at intestinal pH within 24 hrs. The ex vivo investigation demonstrated a significantly enhanced permeability of CAND, with 94.86% in the micelle formulation compared to 9.03% of the pure drug. In vivo pharmacokinetic analysis showed a 4.11-fold increase in oral bioavailability of CAND compared to the marketed formulation.

CONCLUSION

The CAND-PFLC mixed micelle formulation demonstrated improved performance compared to pure CAND, indicating its potential as a promising oral drug delivery system for the effective treatment of hypertension.

Candesartan exhibits low intrinsic permeation capacity and affects buccal tissue viability and integrity: An ex vivo study in porcine buccal mucosa

Candesartan is a nonpeptide angiotensin II receptor blocker that selectively binds to angiotensin II receptor subtype 1. It is administered orally in its ester form (candesartan cilexetil). However, its poor aqueous solubility results in its low bioavailability; therefore, other routes of administration must be explored. The buccal mucosa has been extensively studied as an alternative route for drug delivery as it improves the bioavailability of drugs administered via the peroral route. Porcine buccal mucosa has been widely used as an ex vivo model to study the permeability of various diffusants; however, studies on candesartan are limited. This study aimed to evaluate the ex vivo permeation profile of candesartan and its effects on the viability and integrity of porcine buccal mucosa. Initially, we evaluated the viability, integrity, and barrier function of the buccal tissue before performing permeability tests using freshly excised tissues or tissues after 12 h of resection. Here, three indicators were used: caffeine, β-estradiol, and FD-20 penetration; mucosal metabolic activity, as determined using MTT reduction assay; and haematoxylin and eosin staining. Our results indicated that the porcine buccal mucosa preserved its viability, integrity, and barrier function before the permeation assay, allowing the passage of molecules with a molecular mass of less than 20 kDa, such as caffeine, but not β-estradiol and FD-20. Furthermore, we analyzed the intrinsic capacity of candesartan to diffuse through the fresh porcine buccal mucosa under two pH conditions. The concentration of candesartan in the receptor chamber of Franz diffusion cell was quantified using ultra-high liquid chromatography. In the permeation assay, candesartan exhibited a low intrinsic permeation capacity that impacted the buccal tissue viability and integrity, suggesting that using the buccal mucosa as an alternative route of administration requires developing a pharmaceutical formulation that reduces the adverse effects on mucosa and increasing the buccal permeability of candesartan.

How to Improve Solubility and Dissolution of Irbesartan by Fabricating Ternary Solid Dispersions: Optimization and In-Vitro Characterization

The purpose of this study is to improve the solubility and dissolution of a poorly soluble drug, Irbesartan, using solid dispersion techniques. For that purpose, different polymers such as Soluplus^®, Kollidon^® VA 64, Kolliphor^® P 407, and Polyinylpyrrolidone (PVP-K30) were used as carriers at different concentrations to prepare solid dispersion formulations through the solvent evaporation method. In order to prepare binary dispersion formulations, Soluplus^® and Kollidon^® VA 64 were used at drug: polymer ratios of 1:1, 1:2, 1:3, and 1:4 (w/w). Saturation solubility of the drug in the presence of used carriers was performed to investigate the quantitative increase in solubility. Dissolution studies were performed to explore the drug release behavior from the prepared dispersions. Additionally, the characterization of the prepared formulations was carried out by performing DSC, SEM, XRD, and FTIR studies. The results revealed that among binary systems, K₄ formulation (Drug: Kollidon^® VA 64 at ratio of 1:4 w/w) exhibited optimal performance in terms of increased solubility, drug release, and other investigated parameters. Furthermore, ternary dispersion formulations of the optimized binary formulation were prepared with two more polymers, Kolliphor^® P 407 and Polyvinylpyrrolidone (PVP-K30), at (Drug: Kollidon^® VA 64:ternary polymer) ratios of 1:4:1, 1:4:2, and 1:4:3 (w/w). The results showed that KPVP (TD₃) exhibited the highest increase in solubility, as well as dissolution rate, among ternary solid dispersion formulations. Results of solubility enhancement by ternary solid dispersion formulations were also supported by FTIR, DSC, XRD, and SEM analysis. Conclusively, it was found that the ternary solid dispersion-based systems were more effective compared to the binary combinations in improving solubility as well as dissolution of a poorly soluble drug (Irbesartan).

Facile microfluidic fabrication and characterization of ethyl cellulose/PVP films with neatly arranged fibers

Much attention and endeavor have been paid to developing biocompatible food packaging films. Here, ethyl cellulose (EC) and polyvinylpyrrolidone (PVP) were fabricated into films through a facile method, microfluidic spinning. Morphology observations showed that the fibers were neatly arranged with an average diameter of 1-4 μm. FTIR and X-ray diffraction analysis suggested the existence of good compatibility and interaction between EC and PVP. Thermogravimetric analysis demonstrated that PVP ameliorates the thermal properties; moreover, the tensile properties were improved, with tensile strength (TS) and Young's modulus up to 11.10 ± 1.04 MPa and 350.16 ± 45.46 MPa, respectively. The optimal formula was EC/PVP (2:3), of which the film displayed an enhanced TS of 4.61 ± 1.15 MPa and a modified water contact angle of 61.8 ± 4.4°, showing fine tensile and hydrophilic performance. This study provides a facile and green film fabrication method promising to be used for food wrapping.

Digestion and absorption properties of Lycium barbarum polysaccharides stabilized selenium nanoparticles

In the present study, the digestion and absorption properties of Lycium barbarum polysaccharides stabilized selenium nanoparticles (LBP-SeNPs) were investigated. The results showed that selenium nanoparticles (SeNPs) exhibited a higher selenium release rate than LBP-SeNPs (p＜0.05) after being digested in the stages of oral cavity, stomach and intestine. During the digestion process, the particle size of the LBP-SeNPs and SeNPs were both significantly increased, but the particle size of LBP-SeNPs was significantly smaller than that of SeNPs. The results of TEM further indicated that LBP-SeNPs can better maintain the morphology and properties of nanoparticles. Besides, the experiments of the intestinal sac model showed that LBP-SeNPs can better promote the absorption of selenium in various parts (duodenum, jejunum and ileum) of the intestine. Therefore, the LBP can help to improve the structural stability of SeNPs in the digestion process and improve the bioavailability of selenium.

Enhancement of the dissolution and in-vitro activity of a new antineoplastic agent

The cell-surface molecule CD44 plays a major role in the regulation of cancer stem cells. The CD44 inhibitor compound N'-(1-dimethylaminomethyl-2-oxoindolin-3-ylidene)-2-(benzyloxy)benzohydrazide (OYB), anticancer agent is practically insoluble in water. Hence, the solid dispersion (SD) technique was used for enhancing the dissolution of OYB. The SD of OYB was achieved using OYB:poloxamer 188 (1:7) via the fusion method. The anticancer activities of the free-OYB solution and the SD formulation (OYB-SD) were investigated in-vitro. The dissolution rate of OYB-SD (1:7) increased by two-fold compared with the untreated drug (51.52% to 100% at pH 1.2 and 8.25% to 19.15% at pH 7 buffer). In addition, OYB-SD afforded 3 folds cytotoxic effect, against LoVo cells, compared to the untreated compound (IC50 4.72 ± 0.57 µg/ml and 13.97 ± 0.90 µg/ml respectively) and against HepG2 (∼3-fold) (4.98 ± 0.368 µg/ml and 13.85 ± 1.82 µg/ml respectively) and MCF-7 (1.4-fold) cells (15.20 ± 0.20 µg/ml and 21.12 ± 0.51 µg/ml respectively), and enhanced the apoptotic potential in LoVo cells compared with free-OYB. The improved cytotoxic activity of the drug might be attributable to the enhanced dissolution of OYB.

Formulation and Bioavailability of Novel Mucoadhesive Buccal Films for Candesartan Cilexetil in Rats

Candesartan cilexetil (CC) is an antihypertensive drug. It has low solubility and faces hepatic first-pass metabolism after oral ingestion. We formulated bioadhesive buccal films and studied the respective drug pharmacokinetics. Different bioadhesive films were prepared (40, 80, 120, 160, 200, and 240 mg CC per film) by using the solvent casting method. The drug concentrations used affect the drug entrapment mechanism, which was reflected in the film physicochemical properties like thickness, weight, drug content, bioadhesion, and drug release. Low drug concentration (F2, 40 mg per film) led to minute drug crystal dispersion while increasing the drug concentration (F7, 240 mg per film) showed drug crystal encapsulation, which affects the drug release. The drug pharmacokinetic from the prepared films was studied compared to the oral form by serial blood sampling via an inserted catheter in the carotid of rats. High-Performance Liquid Chromatography assay was used to measure the plasma concentration of CC in different forms. Compared to other films, the F2 showed the highest maximal concentration (Cmax) and the lowest elimination half-life (t_1/2). Bioadhesion buccal film of CC has better bioavailability, especially at low concentrations. The ease, robustness, and ruggedness of the preparation suggests the same procedure for drugs like CC.

Phytophospholipid Complex of Caffeic Acid: Development, In vitro Characterization, and In Vivo Investigation of Antihyperlipidemic and Hepatoprotective Action in Rats

Caffeic acid (CA), a hydroxycinnamic acid possessing a variety of pharmacological activities, has caused a growing interest for the treatment of hyperlipidemia and associated conditions. This work endeavored to develop a novel formulation of CA-Phospholipon® 90H complex (CA-PC) using a solvent evaporation method. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectrophotometry (FTIR), and powder X-ray powder diffraction (PXRD) was carried to confirm the formation of CA-PC. The CA-PC was functionally evaluated in terms of solubility, in vitro and ex vivo drug release, and in vivo bioavailability and efficacy studies. SEM, DSC, FTIR, and XRD studies indicated the physical interaction of CA with Phospholipon® 90H to form a complex. Dynamic light scattering (DLS) studies described particle size of 168 ± 3.9 nm with a monodisperse distribution (PDI 0.17) and a negative zeta-potential of - 16.6 ± 2.1 mV. The phospholipid complex significantly improved (4.2-fold) the solubility of CA. In vitro and ex vivo dissolution studies of the formulated CA-PC revealed a significantly higher release compared with the pure CA. The pharmacokinetic study of CA-PC in rats demonstrated a significant increase (4.79-fold) in oral bioavailability when compared with pure CA as well. Additionally, a significant improvement in serum lipid profile, serum liver biomarker enzyme levels and, restoration of hepatic tissue architecture to normal, in high-fat diet (HFD) induced hyperlipidemic model was obtained upon CA-PC administration when compared with pure CA. These findings indicated that CA-PC would serve as an effective and promising formulation for CA delivery with improved antihyperlipidemic and hepatoprotective activity.Graphical abstract.

Enhancing the Oral Bioavailability of Candesartan Cilexetil Loaded Nanostructured Lipid Carriers: In Vitro Characterization and Absorption in Rats after Oral Administration

Candesartan Cilexetil (CC) is a prodrug widely used in the treatment of hypertension and heart failure, but it has some limitations, such as very poor aqueous solubility, high affinity to P-glycoprotein efflux mechanism, and hepatic first-pass metabolism. Therefore, it has very low oral bioavailability. In this study, glyceryl monostearate (GMS) and Capryol™ 90 were selected as solid and liquid lipids, respectively, to develop CC-NLC (nanostructured lipid carrier). CC was successfully encapsulated into NLP (CC-NLC) to enhance its oral bioavailability. CC-NLC was formulated using a hot homogenization-ultrasonication technique, and the physicochemical properties were characterized. The developed CC-NLC formulation was showed in nanometric size (121.6 ± 6.2 nm) with high encapsulation efficiency (96.23 ± 3.14%). Furthermore, it appeared almost spherical in morphology under a transmission electron microscope. The surgical experiment of the designed CC-NLC for absorption from the gastrointestinal tract revealed that CC-NLC absorption in the stomach was only 15.26% of that in the intestine. Otherwise, cellular uptake study exhibit that CC-NLCs should be internalized through the enterocytes after that transported through the systemic circulation. The pharmacokinetic results indicated that the oral bioavailability of CC was remarkably improved above 2-fold after encapsulation into nanostructured lipid carriers. These results ensured that nanostructured lipid carriers have a highly beneficial effect on improving the oral bioavailability of poorly water-soluble drugs, such as CC.

Oral Bioavailability Enhancement and Anti-Fatigue Assessment of the Andrographolide Loaded Solid Dispersion

Andrographolide (AG), a major diterpene lactone isolated from Andrographis paniculata (Burm. f.) Nees (Acanthaceae), possesses a wide spectrum of biological activities. However, its poor water solubility and low bioavailability limit its clinical application. Therefore, this study aimed to develop a solid dispersion (SD) formulation to increase the aqueous solubility and dissolution rate of AG. Different drug-polymer ratios were used to prepare various SDs. The optimized formulation was characterized for differential scanning calorimetry, Fourier transform infrared spectroscopy, and powder X-ray diffraction. The analysis indicated that the optimized SD enhanced AG solubility and dissolution rates by changing AG crystallinity to an amorphous state. The dissolution behaviors of the optimum SD composed of an AG-polyvinylpyrrolidone K30-Kolliphor EL ratio of 1:7:1 (w/w/w) resulted in the highest accumulated dissolution (approximately 80%). Pharmacokinetic studies revealed that C_max/dose and the AUC/dose increased by 3.7-fold and 3.0-fold, respectively, compared with AG suspension. Furthermore, pretreatment using the optimized AG-SD significantly increased the swimming time to exhaustion by 1.7-fold and decreased the plasma ammonia level by 71.5%, compared with the vehicle group. In conclusion, the optimized AG-SD formulation appeared to effectively improve its dissolution rate and oral bioavailability. Moreover, the optimized AG-SD provides a promising treatment against physical fatigue.

In vitro and in situ study on characterization and mechanism of the intestinal absorption of 2,3,5,4'-tetrahydroxy-stilbene-2-O-β-D-glucoside

Background

2,3,5,4′-tetrahydroxystilbence-2-O-β-D-glucoside (TSG) is a polyhydroxyphenolic compound, which exhibited a broad spectrum of pharmacological activities, such as anti-inflammatory, anti-depression, anti-oxidation and anti-atherosclerosis. However, the compound had poor bioavailability and the underlying absorption mechanisms had not been studied. Therefore, the purpose of this study was to investigate the intestinal absorption mechanism of TSG.

Methods

This study used Caco-2 cell monolayer model and single-pass intestinal perfusion model to explore the gastrointestinal absorption mechanisms of TSG. The effects of basic parameters such as drug concentration, time and pH on the intestinal absorption of TSG were analyzed by high performance liquid chromatography. The absorption susceptibility of TSG to three inhibitors, P-gp inhibitors verapamil hydrochloride and quinidine, and MRP2 inhibitor probenecid were also assessed.

Results

TSG was poorly absorbed in the intestines and the absorption of TSG in stomach is much higher than that in intestine. Both in vitro and in situ experiments showed that the absorption of TSG was saturated with increasing concentration and it was better absorbed in a weakly acidic environment pH 6.4. Moreover, TSG interacts with P-gp and MRP2, and TSG was not only the substrate of the P-gp and MRP2, but also affected the expression of P-gp and MRP2.

Conclusions

It was concluded that the gastrointestinal absorption the most unique active ingredient and considered as the mechanisms of TSG involved processes passive transport and the participation of efflux transporters.

A Self-Nanoemulsifying Drug Delivery System for Enhancing the Oral Bioavailability of Candesartan Cilexetil: Ex Vivo and In Vivo Evaluation

The drug delivery of candesartan cilexetil encounters an obstacle of low absolute oral bioavailability which is attributed mainly to its low aqueous solubility and efflux by intestinal P-glycoprotein (P-gp) transporters. However, the extent of P-gp contribution in the reduced oral bioavailability of candesartan cilexetil is not clear. In this study, a previously developed candesartan cilexetil-loaded self-nanoemulsifying drug delivery system (SNEDDS) was evaluated for its ability to increase the drug oral bioavailability via the inhibition of intestinal P-gp transporters. Despite the developed SNEDDS showing P-gp inhibition activity, P-gp-mediated efflux was found to have a minor role in the reduced oral bioavailability of candesartan cilexetil. On the other hand, the high surfactant concentration used in SNEDDS formulation represents a major challenge toward their widespread application especially for chronically administered drugs. The designed acute and subacute toxicity studies revealed that the degree of intestinal mucosal damage decreases as the treatment period increases. The latter observation was attributed to the reversibility of surfactant-induced mucosal damage. Thus, the developed SNEDDS could be considered as a promising delivery system for enhancing the oral bioavailability of chronically administered drugs.

Pharmaceutical Cocrystal: A Novel Approach to Tailor the Biopharmaceutical Properties of a Poorly Water Soluble Drug

Background:

The present study reports the formation of a cocrystal of candesartan with the coformer methyl paraben, its characterization and determination of its bioavailability. Candesartan is a poorly water-soluble drug having an anti-hypertensive activity. The recent patents on the cocrystals of the drugs Progesterone (US9982007B2), Epalrestat (EP2326632B1), Gefitinib (WO2015170345A1), and Valsartan (CN102702118B) for enhancement of solubility, helped in selection of the drug for this work.

Methods:

Candesartan cocrystal was prepared by solution crystallization method. The formation of a new crystalline phase was characterized by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) and Powder X-ray Diffraction (PXRD) studies. Saturation solubility studies were carried out in ethanol: water (50:50 % v/v) mixture. The dissolution studies were conducted in 900 ml of phosphate buffer at pH 7.4(I.P.) with 0.7% w/w of Tween 20 at 50 rpm, maintained at a temperature of 37±0.5°C in a USP type II dissolution apparatus. The pharmacokinetic behavior of candesartan and its cocrystal was thereof investigated in male Wistar rats.

Results:

There was 6.94 fold enhancement in the solubility of candesartan after its cocrystallization. The dissolution profile of the cocrystal exhibited significant improvement in solubility at 60 and 120 minutes and it remained stable in ethanol: water (50:50%v/v) mixture for 48 h as confirmed by PXRD studies. The AUC0-24of the cocrystal was found to be increased by 2.9 fold in terms of bioavailability as compared to the pure drug.

Conclusion:

The prepared cocrystal was found to be relatively more soluble than the pure drug and also showed an enhanced oral bioavailability as compared to the pure drug.

New sensible method to quantize the intestinal absorption of receptor ligands

In recent years, special attention has been paid to the A₃ adenosine receptor (A₃AR) as a possible pharmacological target to treat intestinal inflammation. In this work, it was set up a novel method to quantify the concentration of a promising anti-inflammatory agent inside and outside of intestinal barrier using the everted gut sac technique. The compound chosen for the present study is one of the most potent and selective A₃AR agonist reported so far, named AR 170 (N⁶-methyl-2-phenylethynyl-5'-N-methylcarboxamidoadenosine). In order to evaluate the intestinal absorption of AR 170 the radioligand binding assay in comparison with HPLC-DAD was used. Results showed that the compound is absorbed via passive diffusion by paracellular pathway. The concentrations determined in the serosal (inside the sac) fluid by radioligand binding assay are in good agreement with those obtained through the widely used HPLC/MS protocol, demonstrating the reliability of the method. It is worthwhile to note that the radioligand binding assay allows detecting very low concentrations of analyte, thus offering an excellent tool to measure the intestinal absorption of receptor ligands. Moreover, the AR 170 quantity outside the gut sac and the interaction with A₃AR could presuppose good topical anti-inflammatory effects of this compound.

In Vitro and In Situ Characterization of the Intestinal Absorption of Capilliposide B and Capilliposide C from Lysimachia capillipes Hemsl

The goal of this investigation was to determine the processes and mechanism of intestinal absorption for capilliposide B (CAPB) and capilliposide C (CAPC) from the Chinese herb, Lysimachia capillipes Hemsl. An analysis of basic parameters, such as drug concentrations, time, and behavior in different intestinal segments was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS). The susceptibility of CAPB and CAPC to various inhibitors such as P-glycoprotein (P-gp) inhibitor (verapamil); multidrug resistance-associated protein 2 (MRP2) inhibitor (indomethacin); cytochrome P450 protein 3A4 (CYP3A4) inhibitor (ketoconazole); and the co-inhibitor of P-gp, MRP2 and CYP3A4 (cyclosporine A) were assessed using both caco-2 cell monolayer and single-pass intestinal perfusion (SPIP) models. As a result, CAPB and CAPC are both poorly absorbed in the intestines and exhibited segment-dependent permeability. The intestinal permeability of CAPB and CAPC were significantly increased by the co-treatment of verapamil, indomethacin. In addition, the intestinal permeability of CAPB was also enhanced by ketoconazole and cyclosporine A. It can be concluded that the intestinal absorption mechanisms of CAPB and CAPC involve processes such as facilitated passive diffusion, efflux transporters, and enzyme-mediated metabolism. Both CAPB and CAPC are suggested to be substrates of P-gp and MRP2. However, CAPB may interact with the CYP3A4 system.

Ex-vivo intestinal absorption study of boswellic acid, cyclodextrin complexes and poloxamer solid dispersions using everted gut sac technique

Acetyl- Keto-β-boswellic acid (AKBA) is a pentacyclic triterpenic acid found in gum resin of Boswellia serrata. Even though it is shown to have anti-inflammatory activity, its bioavailability gets limited due to its poor aqueous solubility and permeability. The present study, hence, deals in enhancement of the intestinal absorption of AKBA from total boswellic acid fraction (TA fraction) using cyclodextrin (CD) and poloxamer solid dispersion (PXM SDs) formulations. Absorption studies were performed using the everted gut sac model prepared from rat jejunum. The glucose uptake assay was performed to show viability of gut sac tissue. The apparent permeability (P_app) value of AKBA from TA fraction was 1.08 ± 0.17 × 10^-6 which was found to be increased by 10-14 fold with CD complex and SD formulations. The intestinal absorption studies showed highest absorption of AKBA from HP-β-CD complex and PXM 407 SD as compared to that from TA fraction. From this study, it can be concluded that HP-β-CD and PXM 407 effectively enhanced intestinal absorption through improved solubility, highlighting their role as efficient drug delivery agents and bioavailability enhancers.

Polymorphic and Quantum Chemistry Characterization of Candesartan Cilexetil: Importance for the Correct Drug Classification According to Biopharmaceutics Classification System

The recommended method for the biopharmaceutical evaluation of drug solubility is the shake flask; however, there are discrepancies reported about the solubility of certain compounds measured with this method, one of them is candesartan cilexetil. The present work aimed to elucidate the solubility of candesartan cilexetil by associating others assays such as stability determination, polymorphic characterization and in silico calculations of intrinsic solubility, ionized species, and electronic structures using quantum chemistry descriptors (frontier molecular orbitals and Fukui functions). For the complete biopharmaceutical classification, we also reviewed the permeability data available. The polymorphic form used was previously identified as the form I of candesartan cilexetil. The solubility was evaluated in biorelevant media in the pH range of 1.2-6.8 at 37.0°C according to the stability previously assessed. The solubility of candesartan cilexetil is pH dependent and the dose/solubility ratios obtained demonstrated the low solubility of the prodrug. The in silico calculations supported the found results and evidenced the main groups involved in the solvation, benzimidazole, and tetrazol-biphenyl. The human absolute bioavailability reported demonstrates that candesartan cilexetil has low permeability and when associated with the low solubility allows to classify it as class 4 of the Biopharmaceutics Classification System.

Segmental-Dependent Intestinal Drug Permeability: Development and Model Validation of In Silico Predictions Guided by In Vivo Permeability Values

The goal of this work was to develop an in silico model that allows predicting segmental-dependent permeability throughout the small intestine (SI). In vivo permeability of 11 model drugs in 3 SI segments (jejunum, mid-SI, ileum) was studied in rats, creating a data set that reflects the conditions throughout the SI. Then, a predictive model was developed, combining physicochemical drug properties influencing the underlying mechanism of passive permeability: Log p, polar surface area, M_W, H-bond count, and Log f_u, with microenvironmental SI conditions. Excellent correlation was evident between the predicted and experimental data (R² = 0.914), with similar predictability in each SI segment. Log p and Log f_u were identified as the major determinants of permeability, with similar contribution. Total H-bond count was also a significant determinant, followed by polar surface area and M_W. Leaving out any of the model parameters decreased its predictability. The model was validated against 5 external drugs, with excellent predictability. Notably, the model was able to predict the segmental-dependent permeability of all drugs showing this trend experimentally. Model predictability was better in the high-permeability versus low-permeability range. Overall, our approach of constructing a straightforward in silico model allowed reliable predictions of segmental-dependent intestinal permeability, providing new insights into relative effects of drug-related factors and gastrointestinal environment on permeability.

Investigation of the synergistic effects of haloperidol combined with Calculus Bovis Sativus in treating MK-801-induced schizophrenia in rats

Clinical studies that focused on treating schizophrenia showed that Calculus Bovis Sativus (CBS), a substitute of Calculus Bovis, when used in combination with haloperidol could significantly lower the dosage of haloperidol compared with treatment with haloperidol alone, whereas efficacy was maintained. The aim of this study was to investigate the synergetic anti-schizophrenia effects in rats using CBS in combination with haloperidol. An open field test was conducted to verify the pharmacodynamic effects of a combination treatment of CBS and haloperidol on MK-801-induced schizophrenic rats. Rat plasma concentrations of intragastric haloperidol and intravenous haloperidol were determined after oral administration of a single dose or 1-week of pretreatment with CBS (50 mg/kg). The pharmacodynamic data showed a significant decrease in locomotor activity and an increase in the percentage of the central distance when haloperidol was concomitantly administered with CBS compared with haloperidol administration alone. The AUC0-∞ and Cmax of haloperidol in the orally coadministered groups were significantly higher compared with the oral treatment with haloperidol alone. In conclusion, oral coadministration of CBS with haloperidol resulted in a synergistic effect in rats. The enhanced oral bioavailability of haloperidol when combined with CBS might be attributed to the interaction between them.

Role of P-Glycoprotein Inhibitors in the Bioavailability Enhancement of Solid Dispersion of Darunavir

Objective

The aim of the present study was to improve bioavailability of an important antiretroviral drug, Darunavir (DRV), which has low water solubility and poor intestinal absorption through solid dispersion (SD) approach incorporating polymer with P-glycoprotein inhibitory potential.

Methods

A statistical approach where design of experiment (DoE) was used to prepare SD of DRV with incorporation of P-glycoprotein inhibitors. Using DoE, different methods of preparation, like melt, solvent evaporation, and spray drying method, utilizing carriers like Kolliphor TPGS and Soluplus were evaluated. The optimized SD was characterized by DSC, FTIR, XRD, and SEM and further evaluated for enhancement in absorption using everted gut sac model, effect of food on absorption of DRV, and in vivo prospect.

Results and Discussion

DSC, FTIR, XRD, and SEM confirmed the amorphicity of drug in SD. Oral bioavailability studies revealed better absorption of DRV when given with food. Absorption studies and in vivo study findings demonstrated great potential of Kolliphor TPGS as P-glycoprotein inhibitor for increasing intestinal absorption and thus bioavailability of DRV.

Conclusion

It is concluded that SD of DRV with the incorporation of Kolliphor TPGS was potential and promising approach in increasing bioavailability of DRV as well as minimizing its extrusion via P-glycoprotein efflux transporters.

Development and in vitro/in vivo performance of self-nanoemulsifying drug delivery systems loaded with candesartan cilexetil

Candesartan cilexetil is widely used in the management of hypertension and heart failure. The drug delivery encounters obstacles of poor aqueous solubility, efflux by intestinal P-glycoprotein and vulnerability to enzymatic degradation in small intestine. Self-nanoemulsifying drug delivery systems (SNEDDS) loaded with candesartan cilexetil were successfully developed to overcome such obstacles. Preliminary screening was carried out to select proper surfactant, co-surfactant and oil combination for successful SNEDDS formulation. All screened excipients were reported for their P-glycoprotein and cytochrome P450 3A4 (CYP3A4) modulation activity. Ternary and pseudo ternary diagrams were constructed to optimize the system. Peppermint oil and clove oil showed a high emulsification ability. The nature of obtained dispersions was identified to be nanoemulsions. Twenty-four formulations were evaluated for stability, robustness to dilution and self-emulsification efficiency. All formulations showed a very short emulsification time of <2min. The emulsification efficiency was significantly superior at pH6.8, at which the largest self-emulsifying region was also observed. Eight formulations were selected for further characterization according to cloud point measurement; mean droplet size, poly dispersity index (PDI) and zeta potential determination in addition to in vitro drug release study. All selected formulations showed very high cloud points (70-90°C), ultrafine mean droplet size (12±1.4 to 24.5±2.13nm), very low PDI values (0.015-0.1305) and almost a complete drug release after 12h. Formulation F15 (Peppermint oil 55% w/w: Cremophor RH40 25% w/w: Labrasol 20% w/w) was selected for further characterization. Its droplet size showed robustness to different dilution folds with different media and its TEM photograph showed spherical particles without any apparent aggregation even after 24h. Formulation F15 successfully controlled the systolic blood pressure of hypertensive rats for 24h with the maximum effect was observed after 2h. These results indicate that, SNEDDS could be promising delivery systems with a rapid onset of action and prolonged therapeutic effect of candesartan cilexetil.

Design and development and evaluation of candesartan cilexetil liquid filling formulations

Most of the currently available drugs are having poor water solubility and suffer from low oral bioavailability. One of the most promising approaches to deliver such insoluble drugs is by dissolving it in lipids, liquids or semi-solids to formulate new products.[1] Candesartan meets the requirement of high potency but it is poorly absorbed when administered as tablets. Therefore the prodrug Candesartan cilexitil is developed.[2] Two piece hard gelatin liquid filling capsules are one of the most logical approaches when choosing the best dosage form to deliver these new liquid formulations.[1] Liquid filled formulations were prepared by employing different cosolvents and surfactants. The formulation containing SLS-2%, PVP- 17.5%, PEG-15%, and PG-53% exhibited desire solubility, rheological property and found to be stable in hard gelatin capsules.

Systematic development of novel cationic self-nanoemulsifying drug delivery systems of candesartan cilexetil with enhanced biopharmaceutical performance

The current studies entail systematic development, optimization and evaluation of cationic self-nanoemulsifying drug delivery systems (C-SNEDDS) for enhancing the oral bioavailability of candesartan cilexetil.