Excipients enhance intestinal absorption of ganciclovir by P-gp inhibition: Assessed in vitro by everted gut sac and in situ by improved intestinal perfusion

Exploring the Impact of Pharmaceutical Excipient PEG400 on the Pharmacokinetics of Mycophenolic Acid Through In Vitro and In Vivo Experiments

Mycophenolic acid (MPA) is a commonly used immunosuppressant. In the human body, MPA is metabolized into mycophenolic acid 7-O-glucuronide (MPAG) and mycophenolic acid acyl-glucuronide (AcMPAG) mainly through liver glucuronidation, which involves UDP-glucuronosyltransferase (UGTs) and transfer proteins. Research has indicated that the pharmaceutical excipient PEG400 can impact drug processes in the body, potentially affecting the pharmacokinetics of MPA. Due to the narrow therapeutic window of MPA, combination therapy is often used, and PEG400 is widely used in pharmaceutical preparations. Therefore, investigating the pharmacokinetic influence of PEG400 on MPA could offer valuable insights for optimizing MPA's clinical use. In this study, we examined the impact of a single oral dose of PEG400 on the blood levels of MPA in rats through pharmacokinetic analysis. We also investigated the distribution of MPA in various tissues using mass spectrometry imaging. We explored the potential mechanism by which PEG400 affects the metabolism of MPA using hepatic and intestinal microsomes and the Caco-2 cellular transporter model. Our findings reveal that the overall plasma concentrations of MPA were elevated in rats following the co-administration of PEG400, with the AUC0-t of MPA and its metabolite MPAG increasing by 45.53% and 29.44%, respectively. Mass spectrometry imaging showed increased MPA content in tissues after PEG400 administration, with significant differences in the metabolites observed across different tissues. Microsomal and transport experiments showed that PEG400 accelerated the metabolism of MPA, promoted the uptake of MPA, and inhibited efflux. In conclusion, PEG400 alters the in vivo metabolism of MPA, potentially through the modulation of metabolic enzymes and transport.

Dual-modified starch micelles as nanocarriers for efficient encapsulation and controlled release of walnut-derived active peptides

Hydrophilic and hydrophobic modified nanomicelles might be more conducive to passage of the gastrointestinal barrier than walnut peptide (WP). In this study, a novel double modified starch polymer, SB-CST-DCA, was synthesized by grafting sulfabetaine (SB) and deoxycholic acid (DCA) onto corn starch (CST) molecules through etherification and esterification. The modification mechanism was discussed to determine its chemical structure, morphological properties, and thermal stability. Peptide-loaded nanomicelles (SB-CST-DCA-WP) were prepared using WP as the core material. The encapsulation efficiency and peptide loading amount reached 76.90 ± 1.52% and 18.27 ± 0.53%, respectively, with good stability and pH-responsive release behavior observed to effectively control WP release and enhance its antioxidant activity. The composite exhibited safety, non-toxicity, and good blood compatibility at concentrations below 125 μg/mL. Duodenum was identified as the main absorption site with an absorption ratio of 41.16 ± 0.36%.

The ATP-Binding Cassette Transporter-Mediated Efflux Transport of Ganciclovir at the Blood-Brain Barrier

BACKGROUND AND OBJECTIVE

Recent studies have highlighted the key role of the ATP-binding cassette (ABC) transporters, including the P-glycoprotein (P-gp), the breast cancer resistance protein (BCRP), and the multi-drug resistance protein 4 (MRP4) in limiting the brain distribution of several antiviral agents. In this study, we investigated whether the inhibition of these transporters increases the permeability of the blood-brain barrier (BBB) to ganciclovir.

METHODS

A microdialysis and high-performance liquid chromatographic method was developed to monitor the concentrations of unbound ganciclovir in the brain interstitial fluid and plasma, with and without the administration of ABC transporter inhibitors. Pharmacokinetic parameters, including the area under the plasma concentration-time curve from time 0 to time of the last measurable analyte concentration (AUC0-t,plasma), the area under the brain interstitial fluid concentration-time curve from time 0 to time of the last measurable analyte concentration (AUC0-t,brain), and the unbound brain-to-plasma concentration ratio (Kp,uu,brain) were calculated.

RESULTS

The mean AUC0-t,plasma, AUC0-t,brain, and Kp,uu,brain in rats who received ganciclovir (30 mg/kg, intraperitoneal) alone were 1090 min·µg/mL, 150 min·µg/mL, and 14%, respectively. After the administration of tariquidar (inhibitor of P-gp), Ko143 (inhibitor of BCRP), or MK-571 (inhibitor of MRP4), the Kp,uu,brain of ganciclovir increased to 31 ± 2.1%, 26 ± 1.3%, and 32 ± 2.0%, respectively.

CONCLUSIONS

The findings of this study suggest that ABC transporters P-gp, BCRP, and MRP4 mediate the efflux of ganciclovir at the BBB and that the inhibition of these transporters facilitates the penetration of the BBB by ganciclovir.

CNS Viral Infections-What to Consider for Improving Drug Treatment: A Plea for Using Mathematical Modeling Approaches

Neurotropic viruses may cause meningitis, myelitis, encephalitis, or meningoencephalitis. These inflammatory conditions of the central nervous system (CNS) may have serious and devastating consequences if not treated adequately. In this review, we first summarize how neurotropic viruses can enter the CNS by (1) crossing the blood-brain barrier or blood-cerebrospinal fluid barrier; (2) invading the nose via the olfactory route; or (3) invading the peripheral nervous system. Neurotropic viruses may then enter the intracellular space of brain cells via endocytosis and/or membrane fusion. Antiviral drugs are currently used for different viral CNS infections, even though their use and dosing regimens within the CNS, with the exception of acyclovir, are minimally supported by clinical evidence. We therefore provide considerations to optimize drug treatment(s) for these neurotropic viruses. Antiviral drugs should cross the blood-brain barrier/blood cerebrospinal fluid barrier and pass the brain cellular membrane to inhibit these viruses inside the brain cells. Some antiviral drugs may also require intracellular conversion into their active metabolite(s). This illustrates the need to better understand these mechanisms because these processes dictate drug exposure within the CNS that ultimately determine the success of antiviral drugs for CNS infections. Finally, we discuss mathematical model-based approaches for optimizing antiviral treatments. Thereby emphasizing the potential of CNS physiologically based pharmacokinetic models because direct measurement of brain intracellular exposure in living humans faces ethical restrictions. Existing physiologically based pharmacokinetic models combined with in vitro pharmacokinetic/pharmacodynamic information can be used to predict drug exposure and evaluate efficacy of antiviral drugs within the CNS, to ultimately optimize the treatments of CNS viral infections.

In vitro and in vivo characterization of human serum albumin-based PEGylated nanoparticles for BDNF and NT3 codelivery

The utilization of neurotrophins in medicine shows significant potential for addressing neurodegenerative conditions, such as age-related macular degeneration (AMD). However, the therapeutic use of neurotrophins has been restricted due to their short half-life. Here, we aimed to synthesize PEGylated nanoparticles based on electrostatic-driven interactions between human serum albumin (HSA), a carrier for adsorption; neurotrophin-3 (NT3); and brain-derived neurotrophic factor (BDNF). Electrophoretic (ELS) and multi-angle dynamic light scattering (MADLS) revealed that the PEGylated HSA-NT3-BDNF nanoparticles ranged from 10 to 430 nm in diameter and exhibited a low polydispersity index (<0.4) and a zeta potential of -8 mV. Based on microscale thermophoresis (MST), the estimated dissociation constant (Kd) from the HSA molecule of BDNF was 1.6 μM, and the Kd of NT3 was 732 μM. The nanoparticles were nontoxic toward ARPE-19 and L-929 cells in vitro and efficiently delivered BDNF and NT3. Based on the biodistribution of neurotrophins after intravitreal injection into BALB/c mice, both nanoparticles were gradually released in the mouse vitreous body within 28 days. PEGylated HSA-NT3-BDNF nanoparticles stabilize neurotrophins and maintain this characteristic in vivo. Thus, given the simplicity of the system, the nanoparticles may enhance the treatment of a variety of neurological disorders in the future.

Can Ganciclovir and Quercetin-P188 Ameliorate Cytomegalovirus Induced Hearing Loss?

OBJECTIVE

Determine whether combination therapy with ganciclovir (GCV) and a Quercetin-P188 solution improves hearing outcomes in a murine cytomegalovirus (CMV) model.

METHODS

BALB/c mice were infected with murine CMV on postnatal day 3 (p3). Quercetin was solubilized in saline using P188 (QP188). Treatment groups received either GCV, QP188, GCV and QP188, or P188 delivery vehicle BID at 12-hour intervals via intraperitoneal injection. All treatment groups were treated for 14 days starting at p3. Uninfected controls were treated with the combined regimen, saline or P188 delivery vehicle. Auditory thresholds were assessed using distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) testing at 4, 6, and 8 weeks of age. Temporal bones from separate CMV-infected groups were harvested at p10, and viral load was determined by quantitative polymerase chain reaction.

RESULTS

CMV-infected mice receiving combination therapy GCV+QP188 demonstrated statistically significant lower ABR (p < 0.001) and DPOAE thresholds (p < 0.001) compared with mice treated with GCV monotherapy, QP188 monotherapy, and P188 delivery vehicle at 4, 6, and 8 weeks of age. GCV+QP188 combination therapy, GCV monotherapy, and QP188 monotherapy resulted in a nonsignificant reduction in mean viral titers compared to P188 monotherapy (p = 0.08).

CONCLUSION

Combining GCV with the excipients quercetin and P188 effectively ameliorated CMV-induced sensorineural hearing loss in a murine model. This result may be partially explained by a reduction in viral titers in mouse temporal bones that correlate with in vitro studies demonstrating additive antiviral effect in cell culture.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1457-1463, 2024.

A critical review of a typical research system for food-derived metal-chelating peptides: Production, characterization, identification, digestion, and absorption

In the past decade, food-derived metal-chelating peptides (MCPs) have attracted significant attention from researchers working towards the prevention of metal (viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting the precipitation of metals caused by the gastrointestinal environment and exogenous substances (including phytic and oxalic acids). However, for the improvement of limits of current knowledge foundations and future investigation directions of MCP or their derivatives, several review categories should be improved and emphasized. The species' uniqueness and differences in MCP productions highly contribute to the different values of chelating ability with particular metal ions, whereas comprehensive reviews of chelation characterization determined by various kinds of technique support different horizons for explaining the chelation and offer options for the selection of characterization methods. The reviews of chelation mechanism clearly demonstrate the involvement of potential groups and atoms in chelating metal ions. The discussions of digestive stability and absorption in various kinds of absorption model in vitro and in vivo as well as the theory of involved cellular absorption channels and pathways are systematically reviewed and highlighted compared with previous reports as well. Meanwhile, the chelation mechanism on the molecular docking level, the binding mechanism in amino acid identification level, the utilizations of everted rat gut sac model for absorption, and the involvement of cellular absorption channels and pathway are strongly recommended as novelty in this review. This review makes a novel contribution to the literature by the comprehensive prospects for the research and development of food-derived mineral supplements.

Study on the transport and internalisation mechanism of dietary supplement nattokinase in the small intestine using animal and Caco-2 cell monolayer models

Maintaining proper blood flow is critical to promoting good health. Nattokinase is a serine protease from Bacillus subtilis that has significant in vitro thrombolytic activity, but its mechanism as a dietary supplement to prevent thrombosis through intestinal absorption and transport is still unclear.The purpose of this study is to study the transport and internalisation mechanism of NK in the small intestine using animal models and Caco-2 cell monolayer models.This study first evaluated the preventive effect of supplementing low dose (4000 FU (Fibrin Unit)/kg, n = 6), medium dose (8000 FU/kg, n = 6), and high dose (12000 FU/kg, n = 6) of nattokinase on carrageenan induced thrombosis in mice. Subsequently, we used the rat gut sac model, ligated intestinal loop model, and Caco-2 cell uptake model to study the intestinal transport mechanism of NK.Results indicate that NK is a moderately absorbed biomolecule whose transport through enterocytes is energy- and time-dependent. Chlorpromazine, nystatin and EIPA all inhibited the endocytosis of NK to varying degrees, indicating that the endocytosis of NK in Caco-2 cells involves macropinocytosis, clathrin-mediated and caveolae-mediated pathway. These findings offer a theoretical basis for investigating the mechanism of oral NK supplementation in greater depth.

Liposomes for the Treatment of Brain Cancer-A Review

Due to their biocompatibility, non-toxicity, and surface-conjugation capabilities, liposomes are effective nanocarriers that can encapsulate chemotherapeutic drugs and facilitate targeted delivery across the blood-brain barrier (BBB). Additionally, strategies have been explored to synthesize liposomes that respond to internal and/or external stimuli to release their payload controllably. Although research into liposomes for brain cancer treatment is still in its infancy, these systems have great potential to fundamentally change the drug delivery landscape. This review paper attempts to consolidate relevant literature regarding the delivery to the brain using nanocarriers, particularly liposomes. The paper first briefly explains conventional treatment modalities for cancer, followed by describing the blood-brain barrier and ways, challenges, and techniques involved in transporting drugs across the BBB. Various nanocarrier systems are introduced, with attention to liposomes, due to their ability to circumvent the challenges imposed by the BBB. Relevant studies involving liposomal systems researched to treat brain tumors are reviewed in vitro, in vivo, and clinical studies. Finally, the challenges associated with the use of liposomes to treat brain tumors and how they can be addressed are presented.

The passive diffusion improvement of Vitamin B12 intestinal absorption by Gelucire that fit for commercialized production

Vitamin B₁₂ (VB₁₂) is a vital micronutrient to maintain the normal state of the hematopoietic system. It must be obtained from the diet since the human body cannot synthesize it. Moreover, the absorption of VB₁₂ needs to be mediated by intrinsic factor on the gastrointestinal (GI) track. The abnormalities in the stomach or lack of such intrinsic factors may result in poor oral absorption of VB₁₂. However, the very advanced formulation strategies were generally very costly and still in the development stage. Thus, the objectives of the present study were to increase the VB₁₂ intestinal absorption by conventional excipients of Gelucire 44/14 (G44/14) or Labrasol, which could be potentially formulated as a cost effect balanced product. The in vitro Caco-2 cell model was applied for the absorption study. A novel VB₁₂ solid dispersion was subsequently prepared and further characterized by Differential scanning calorimetry, Fourier transform infrared spectroscopy, and Scanning electron microscopy, respectively. The membrane permeability of the VB₁₂ solid dispersion was finally evaluated using ex vivo rat everted gut sac method. The results suggested that G44/14 could significantly enhance the intestinal absorption of VB₁₂ via P-glycoprotein inhibition in vitro (P < 0.01). The membrane permeability of VB₁₂could be significantly (P < 0.01) improved by G44/14-VB₁₂ solid dispersion at a proportion of carrier: drug ratio of 20:1.The liquidfied solid dispersion was finally directly filled in the hard gelatin capsules. In conclusion, the cheap and simplified process of VB₁₂ complex prepared by G44/14 could potentially increase VB₁₂ intestinal absorption, which may be liable to commercial manufacturing.

A Study on Pharmacokinetic Functionalities and Safety Margins of an Optimized Simvastatin Nanoformulation

A pharmaceutical formulation with favorable pharmacokinetic parameters is more likely to be efficacious and safe to overcome the failures of the drug resulting from lack of efficacy, poor bioavailability, and toxicity. In this view, we aimed to evaluate the pharmacokinetic functionalities and safety margin of an optimized CS-SS nanoformulation (F40) by in vitro/in vivo methods. The everted sac technique was used to evaluate the improved absorption of a simvastatin formulation. In vitro protein binding in bovine serum and mice plasma was performed. The formulation’s liver and intestinal CYP3A4 activity and metabolic pathways were investigated by the qRT-PCR technique. The excretion of cholesterol and bile acids was measured to demonstrate the formulation’s cholesterol depletion effect. Safety margins were determined by histopathology as well as fiber typing studies. In vitro protein binding results revealed the existence of a high percentage of free drugs (22.31 ± 3.1%, 18.20 ± 1.9%, and 16.9 ± 2.2%, respectively) compared to the standard formulation. The controlled metabolism in the liver was demonstrated from CYP3A4 activity. The formulation showed enhanced PK parameters in rabbits such as a lower Cmax, clearance, and a higher Tmax, AUC, Vd, and t1/2. qRT-PCR screening further proved the different metabolic pathways followed by simvastatin (SREBP-2) and chitosan (PPAR-γ pathway) in the formulation. The results from qRT-PCR and histopathology confirmed the toxicity level. Hence, this pharmacokinetic profile of the nanoformulation proved it has a unique synergistic hypolipidemic modality.

Preparation and optimization of surface stabilized cryptotanshinone nanocrystals with enhanced bioavailability

Cryptotanshinone (CTS) is a plant product extracted from Salvia miltiorrhiza Bunge with various pharmacological significances. In addition to its activities against coronary heart disease, hyperlipidemia, stroke, hepatitis and chronic renal failure, it demonstrates antimetastatic effects. However, its clinical use is limited due to its poor aqueous solubility and oral bioavailability. Herein, CTS nanocrystals were prepared with the precipitation method followed by high-pressure homogenization using Poloxamer 407 as the stabilizer. A stable product was further obtained by lyophilization. The particle size of the CTS nanocrystals was 315.67 ± 11.02 nm, and the zeta potential was near 0 mV. The crystallinity was confirmed by DSC and PXRD. The saturation solubility was substantially increased from 0.97 ± 0.12 μg/ml to 62.29 ± 1.91 μg/ml, and the dissolution rate was also significantly accelerated. A pharmacokinetic study in rats revealed an improvement in oral bioavailability (2.87-fold) with CTS nanocrystals compared to the raw drug. In conclusion, the results of this study suggest a feasible formulation for the oral delivery of CTS.

Effect of polyethylene glycol 400 on the pharmacokinetics and tissue distribution of baicalin by intravenous injection based on the enzyme activity of UGT1A8/1A9

Baicalin (BG) is a bioactive flavonoid extracted from the dried root of the medicinal plant, Scutellaria radix (SR) (dicotyledonous family, Labiatae), and has several biological activities. Polyethylene glycol 400 (PEG400) has been used as a suitable solvent for several traditional Chinese medicines (TCM) and is often used as an excipient for the compound preparation of SR. However, the drug-excipient interactions between BG and PEG400 are still unknown. Herein, we evaluated the effect of a single intravenous PEG400 administration on the BG levels of rats using pharmacokinetic and tissue distribution studies. A liver microsome and recombinant enzyme incubation system were used to further confirm the interaction mechanism between PEG400 and UDP-glucuronosyltransferases (UGTs) (UGT1A8 and UGT1A9). The pharmacokinetic study demonstrated that following the co-intravenous administration of PEG400 and BG, the total clearance (CL_z) of BG in the rat plasma decreased by 101.60% (p < 0.05), whereas the area under the plasma concentration-time curve (AUC)_0-t and AUC_0-inf increased by 144.59% (p < 0.05) and 140.05% (p < 0.05), respectively. Additionally, the tissue distribution study showed that the concentration of BG and baicalein-6-O-β-D-glucuronide (B6G) in the tissues increased, whereas baicalein (B) in the tissues decreased, and the total amount of BG and its metabolites in tissues altered following the intravenous administration of PEG400. We further found that PEG400 induced the UGT1A8 and UGT1A9 enzyme activities by affecting the maximum enzymatic velocity (V_max) and Michaelis-Menten constant (K_m) values of UGT1A8 and UGT1A9. In conclusion, our results demonstrated that PEG400 interaction with UGTs altered the pharmacokinetic behaviors and tissue distribution characteristics of BG and its metabolites in rats.

Strategies and Mechanism in Reversing Intestinal Drug Efflux in Oral Drug Delivery

Efflux transporters distributed at the apical side of human intestinal epithelial cells actively transport drugs from the enterocytes to the intestinal lumen, which could lead to extremely poor absorption of drugs by oral administration. Typical intestinal efflux transporters involved in oral drug absorption process mainly include P-glycoprotein (P-gp), multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP). Drug efflux is one of the most important factors resulting in poor absorption of oral drugs. Caco-2 monolayer and everted gut sac are sued to accurately measure drug efflux in vitro. To reverse intestinal drug efflux and improve absorption of oral drugs, a great deal of functional amphiphilic excipients and inhibitors with the function of suppressing efflux transporters activity are generalized in this review. In addition, different strategies of reducing intestinal drugs efflux such as silencing transporters and the application of excipients and inhibitors are introduced. Ultimately, various nano-formulations of improving oral drug absorption by inhibiting intestinal drug efflux are discussed. In conclusion, this review has significant reference for overcoming intestinal drug efflux and improving oral drug absorption.

Intestinal metabolism and absorption mechanism of multi-components in Gaultheria leucocarpa var. yunnanensis - An assessment using in situ and in vitro models, comparing gut segments in pathological with physiological conditions

ETHNOPHARMACOLOGICAL RELEVANCE

Dianbaizhu (Gaultheria leucocarpa var. yunnanensis) as a Chinese folk medicine exerts significant treatment effects on rheumatoid arthritis (RA) with a long historical time. Our previous reports showed that the anti-rheumatic arthritis fraction (ARF) extracted and enriched from Dianbaizhu possessed good druggability, which was better than its single active ingredients. However, the intestinal transport characteristics and mechanism of ARF have not been elucidated to date.

AIM OF THE STUDY

In order to illustrate the role of active ingredients of ARF in alleviating RA and promoting the development of dosage forms, the intestinal metabolism, absorption properties and mechanism of ARF in vitro and in situ models were investigated.

MATERIALS AND METHODS

Firstly, after incubating with 4 intestinal segments (duodenum, jejunum, ileum, and colon), 7 key components in ARF, including MATG-B, (+)-catechin, MSTG-A, Gaultherin, chlorogenic acid, quercetin, and kaempferol were quantitatively analyzed by a high-performance liquid chromatography (HPLC). Secondly, combining the physiological and pathological rats, the in situ single-pass intestinal perfusion and in vitro everted gut sacs of rats were performed to investigate the absorption features and transport mechanisms of ARF using HPLC and HPLC-Q-TOF-MS/MS. Subsequently, in situ studies were employed to determine the effect of P-glycoprotein (P-gp) inhibitor (verapamil) on the transport characteristics of ARF in RA model rats.

RESULTS

Comparing the absorption parameters of ARF incubated in different intestinal segments, data showed that the absorption of ARF in the small intestine was significantly stronger than that of the colon (P < 0.01). The number of characterized prototype components was subjected to the incubation time, drug concentration and rat body condition, but not the intestinal segments. There were no significant differences in the number of metabolites among different intestinal segments, administration concentrations and incubation time. The best small intestinal absorption site of ARF was duodenum and ileum in normal and model rats, respectively. The P_eff values of 7 index compounds were all higher than 0.2 × 10^-4cm/s, and the F_a values of 7 index compounds were all greater than 20% in the in situ perfusion investigation. The results showed that MSTG-B, MSTG-A and Gaultherin were likely to be substrates of P-gp as verapamil significantly enhanced their P_eff and K_a values, while other ingredients were not P-gp substrates.

CONCLUSIONS

The intestinal membrane permeability of ARF was good. Its intestinal absorption mechanisms mainly involved active transportation processes and passive diffusion. Besides, this report provided data support and basis for clinical development, bioavailability improvement and formulation design.

Influence of Piperine and Omeprazole on The Regional Absorption of Daclatasvir from Rabbit Intestine

The study assessed the site dependent intestinal absorption of daclatasvir and investigated the effects of piperine and omeprazole on such absorption utilizing in situ rabbit intestinal perfusion technique. The intestinal absorption of daclatasvir was assessed in four segments: duodenum, jejunum, ileum, and colon. The effect of co-perfusion with omeprazole was monitored through the tested anatomical sites. The effect of piperine, a P-glycoprotein (P-gp) inhibitor on daclatasvir absorption from jejunum and ileum was tested. The results showed that daclatasvir was incompletely absorbed from the rabbit small and large intestine. The absorptive clearance per unit length (PeA/L) was site dependent and was ranked as colon > duodenum > jejunum > ileum. This rank is the opposite of the rank of P-gp intestinal content suggesting possible influence for P-gp. Co-perfusion with omeprazole increased PeA/L and this was evidenced also with reduced the L95% of daclatasvir from both small and large intestinal segments. Significant enhancement in daclatasvir absorption through jejunum and ileum was shown in presence of piperine. Daclatasvir showed site dependent intestinal absorption in a manner suggesting its affection by P-gp efflux. This effect was inhibited by piperine. Co-administration of daclatasvir with omeprazole can enhance intestinal absorption a phenomenon which requires extension to human pharmacokinetic investigation. This article is protected by copyright. All rights reserved.

Synthesis, characterization, and pharmacological evaluation of some metal complexes of quercetin as P-gp inhibitors

Background

Six different metal complexes of quercetin (Cu, Zn, Co, Vd, Mo, Ni) were synthesized, purified, and characterized by their physical and spectral (UV, IR) data. They were evaluated for their P-gp (permeability glycoprotein) inhibitory activity by in vitro everted sac method in rats. The apparent permeability of atorvastatin (P-gp substrate) from everted sac of the rat intestine was determined in control, standard (verapamil), and groups treated with quercetin-metal complexes. The drug contents were analyzed by validated RP-HPLC method using a mixture of acetonitrile and water (60:40 v/v) adjusted to pH 2.8 with phosphate buffer as mobile phase.

Results

In vitro studies revealed that the apparent permeability of atorvastatin (P-gp substrate) across the small intestine is much affected by the treatment with Cu/Co/Ni complexes of quercetin. The mean ± SD and apparent permeability of atorvastatin decreased after pre-treatment with these metal complexes.

Conclusions

The quercetin Cu/Co/Ni complexes could inhibit P-gp and increase the atorvastatin absorption. Hence, they could be considered P-gp inhibitors.

Interaction of Commonly Used Oral Molecular Excipients with P-glycoprotein

P-glycoprotein (P-gp) plays a critical role in drug oral bioavailability, and modulation of this transporter can alter the safety and/or efficacy profile of substrate drugs. Individual oral molecular excipients that inhibit P-gp function have been considered a mechanism for improving drug absorption, but a systematic evaluation of the interaction of excipients with P-gp is critical for informed selection of optimal formulations of proprietary and generic drug products. A library of 123 oral molecular excipients was screened for their ability to inhibit P-gp in two orthogonal cell-based assays. β-Cyclodextrin and light green SF yellowish were identified as modest inhibitors of P-gp with IC₅₀ values of 168 μM (95% CI, 118-251 μM) and 204 μM (95% CI, 5.9-1745 μM), respectively. The lack of effect of most of the tested excipients on P-gp transport provides a wide selection of excipients for inclusion in oral formulations with minimal risk of influencing the oral bioavailability of P-gp substrates.

Formulation of Chitosan-Coated Piperine NLCs: Optimization, In Vitro Characterization, and In Vivo Preclinical Assessment

In the present research work, surface-modified nanostructured lipid carriers (NLCs) with chitosan (CH) were prepared to improve the therapeutic efficacy of piperine (PP). NLCs were developed and optimized (CH-PP-NLCs-opt) by design expert software and the selected NLCs surface was coated with chitosan (0.2% w/v). CH-PP-NLCs-opt have shown a particle size of 149.34 ± 4.54 nm and entrapment efficiency of 80.65 ± 1.23%. The results of the solid-state characterization study exhibited that PP enclosed in lipids and present amorphous form. It might be due to the nanoparticle size of NLCs. The drug release study revealed PP-NLCs-opt and CH-PP-NLCs-opt exhibited significant (P < 0.05) difference in PP release (88.87 ± 5.23% and 76.34 ± 4.54%) as compared to pure PP (19.02 ± 2.87%). CH-PP-NLCs-opt exhibited strong bioadhesion than PP-NLCs-opt which has a positive influence the drug permeation and absorption. CH-PP-NLCs-opt showed higher permeation (1083.34 ± 34.15 μg/ cm2) than pure PP (106.65 ± 15.44 μg/cm²) and PP-NLCs-opt (732.45 ± 28.56 μg/ cm²). The significantly enhanced bioavailability of PP was observed from CH-PP-NLCs-opt (3.76- and 1.21-fold) than PP-dispersion and PP-NLCs-opt. The diabetes was induced in rats by a single intraperitoneal administration of streptozotocin (STZ, 40 mg/kg, citrate buffer pH 4.5), and results revealed that PP-NLCs-opt and CH-PP-NLCs-opt reduce the blood glucose level (28.26% and 36.52% respectively) as compared to PP-dispersion (10.87%). It also helps to maintain the altered biochemical parameters. In conclusion, CH-PP-NLC can be a novel oral nanocarrier for the management of diabetes.

Physicochemical Characterization and Biopharmaceutical Evaluation of ZWF: A Novel Anticancer Drug for the Treatment of Non-small Cell Lung Cancer

The orally available novel small molecule drug ZWF is under preclinical development for an anticancer purpose. The present study aimed to assess the viability of developing ZWF as a form of oral formulation for clinical application based on the principles of biopharmaceutics and pharmacokinetics. The crucial physicochemical properties of ZWF were determined by in vitro assays. The in situ gastrointestinal absorption characteristics and in vivo pharmacokinetic behaviors of ZWF in rats were characterized. The solubility of ZWF showed a highly pH-dependent profile, decreasing from 25,392.89 to 20.48 μg/mL as the solution pH increased from 1.0 to 5.8. In PBS with a pH of 1.0 to 5.8, the LogP value of ZWF ranged from -2.35 to 2.20 and was gradually increased as the pH value increased. ZWF was partially absorbed in the stomach, and the favorable absorption sites were the duodenum, jejunum, and ileum. Pharmacokinetic studies showed that the AUC_(0-t) and C_max values of ZWF after its oral administration as a suspension prepared with 0.5% CMC-Na were increased by 18.97% and 40% than that with normal saline, providing a model oral formulation of ZWF with ideal bioavailability and system exposure in rats. From the perspective of oral absorption, ZWF possessed appealing qualities as a drug candidate and could be prepared as an oral preparation for clinical application. The present study has established a fundamental foundation for the development and quality evaluation of the ZWF oral formulations.

Effect of Pharmaceutical Excipients on Intestinal Absorption of Metformin via Organic Cation-Selective Transporters

Growing evidence has shown that some pharmaceutical excipients can act on drug transporters. The present study was aimed at investigating the effects of 13 commonly used excipients on the intestinal absorption of metformin (MTF) and the underlying mechanisms using Caco-2 cells and an ex vivo mouse non-everted gut sac model. First, the uptake of MTF in Caco-2 cells was markedly inhibited by nonionic excipients including Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and crospovidone. Second, transport profile studies showed that MTF was taken up via multiple cation-selective transporters, among which a novel pyrilamine-sensitive proton-coupled organic cation (H⁺/OC⁺) antiporter played a key role. Third, Solutol HS 15, polysorbate 40, and polysorbate 60 showed cis-inhibitory effects on the uptake of either pyrilamine (prototypical substrate of the pyrilamine-sensitive H⁺/OC⁺ antiporter) or 1-methyl-4-phenylpyridinium (substrate of traditional cation-selective transporters including OCTs, MATEs, PMAT, SERT, and THTR-2), indicating that their suppression on MTF uptake is due to the synergistic inhibition toward multiple influx transporters. Finally, the pH-dependent mouse intestinal absorption of MTF was significantly decreased by Solutol HS 15, polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 80, and pyrilamine. In conclusion, this study revealed that a novel transport process mediated by the pyrilamine-sensitive H⁺/OC⁺ antiporter contributes to the intestinal absorption of MTF in conjunction with the traditional cation-selective transporters. Mechanistic understanding of the interaction of excipients with cation-selective transporters can improve the formulation design and clinical application of cationic drugs.

Engineered liposomes targeting the gut-CNS Axis for comprehensive therapy of spinal cord injury

Effective curative therapies for spinal cord injury (SCI), which is often accompanied by intestinal complications, are lacking. Potential therapeutic targets include astrocytes and their enteric nervous system counterpart, enteric glial cells (EGCs). Based on shared biomarkers and similar functions of both cell types, we designed an orally administered targeted delivery system in which the neuropeptide apamin, stabilized by sulfur replacement with selenium, was adopted as a targeting moiety, and the liposome surface was protected with a non-covalent cross-linked chitosan oligosaccharide lactate layer. The system effectively permeated through oral absorption barriers, targeted local EGCs and astrocytes after systemic circulation, allowing for comprehensive SCI therapy. Given the involvement of the gut-organ axis in a growing number of diseases, our research may shed light on new aspects of the oral administration route as a bypass for multiple interventions and targeted therapy.

Effect of excipients on oral absorption process according to the different gastrointestinal segments

INTRODUCTION

Excipients are necessary to develop oral dosage forms of any Active Pharmaceutical Ingredient (API). Traditionally, excipients have been considered inactive and inert substances, but, over the years, numerous studies have contradicted this belief. This review focuses on the effect of excipients on the physiological variables affecting oral absorption along the different segments of the gastrointestinal tract. The effect of excipients on the segmental absorption variables are illustrated with examples to help understand the complexity of predicting their in vivo effects.

AREAS COVERED

The effects of excipients on disintegration, solubility and dissolution, transit time, and absorption are analyzed in the context of the different gastrointestinal segments and the physiological factors affecting release and membrane permeation. The experimental techniques used to study excipient effects and their human predictive ability are reviewed.

EXPERT OPINION

The observed effects of excipient in oral absorption process have been characterized in the past, mainly in vitro (i.e. in dissolution studies, in vitro cell culture methods or in situ animal studies). Unfortunately, a clear link with their effects in vivo, i.e. their impact on Cmax or AUC, which need a mechanistic approach is still missing. The information compiled in this review leads to the conclusion that the effect of excipients in API oral absorption and bioavailability is undeniable and shows the need of implementing standardized and reproducible preclinical tools coupled with mechanistic and predictive physiological-based models to improve the current empirical retrospective approach.

Tailoring lipid nanoconstructs for the oral delivery of paliperidone: Formulation, optimization and in vitro evaluation

PURPOSE

The present research work involves Quality by Design (QbD)-based fabrication of lipid nanoconstructs (LNC) of paliperidone (PPD) bearing superior biopharmaceutical attributes.

METHODS

LNC of paliperidone was prepared by melt emulsification-probe sonication and high-pressure homogenization method followed by optimization using QbD approach. Preparing LNC by both these methods will give the benefit of identifying the best optimized formulation which will be further evaluated for in vitro studies.

RESULTS

The best optimized formulation was obtained using melt emulsification-probe sonication technique with small particle size (86.35 nm), high entrapment efficiency (90.07 %), and high loading capacity (8.49 %). The drug release from LNC was found to be 5, 8, and 9-folds greater than drug suspension in pH 1.2, 6.8, and 7.4 respectively (p < 0.001). Stability studies of LNC in simulated gastric fluid pH 1.2 and fasted state simulated intestinal fluid depicted no alteration in particle size and polydispersity index of LNC but were found to increase in fed state simulated intestinal fluid. The drug permeability through rat intestine for LNC was found to be approximately 6-folds (p < 0.05) greater as compared to the drug suspension which was further confirmed by confocal microscopy. The in vitro lipolysis study presented significantly highest solubilization (p < 0.001) in the aqueous phase thereby anticipating higher in vivo absorption.

CONCLUSION

Thus, it was concluded that LNC bears the knack of improving the solubilization and permeation potential of an otherwise hydrophobic drug, paliperidone."

Hyaluronic Acid in the Intestinal Tract: Influence of Structure, Rheology, and Mucoadhesion on the Intestinal Uptake in Rats

Oral hyaluronic acid (HA) is a ubiquitous biopolymer that has gained attention as a treatment for local or systemic diseases. Here, we prepared and characterized structures of free HA (f-HA) with a high (>105 Da), intermediate (≤105 Da), and low (≤104 Da) average molar mass (MM); nanoparticles crosslinked with adipic dihydrazide (n-HA); and mixed formulations (mixed-HA) containing f-HA and n-HA. MM distribution determined the structure, hydrodynamic diameter, and zeta potential of the f-HAs. Crosslinking changed the physicochemical properties in n-HA. In vitro tack adhesion assays, using mucin tablets or a viable rat intestinal mucosa, showed better mucoadhesion with f-HA (intermediate MM) and mixed-HA (25% n-HA), especially in the jejunum segment. High MM f-HA presented negligible mucoadhesion. n-HA showed the deepest diffusion into the porous of the membranes. In vivo results showed that, except for high MM f-HA, there is an inverse relationship between rheological changes in the intestinal membrane macerates resulting from mucoadhesion and the effective intestinal permeability that led to blood clearance of the structures. We conclude that the n-HA formulations are promising for targeting other tissues, while formulations of f-HA (intermediate MM) and mixed-HA are better for treating dysbiosis.

Toxicity Alleviation of Carbon Dots from Roast Beef after the Formation of Protein Coronas with Human Serum Albumin

The unique properties of nanoparticles produced during food thermal processing have attracted considerable attention. In this study, the formation of protein coronas of fluorescent carbon dots (CDs) in roast beef with human serum albumin (HSA) and the corona effect on toxicity were reported. The CDs were roughly spherical with a size in the range of 1-5 nm, which were mainly composed of carbon (68.68%), nitrogen (10.6%), and oxygen (15.98%). The CDs could readily pass through the intestine wall due to their small size and good water solubility. There was an obvious interaction between HSA and CDs, suggesting that the CDs could form protein coronas. Thermodynamic analysis results of ΔH < 0 (-13.17 ± 3.74 kJ/mol) and ΔS > 0 ( 28.04 J/mol/K) indicated that the binding of HSA-CDs was due to electrostatic interactions or hydrophobic forces. The HSA-CD coronas were distributed in the lysosomes of the cells, alleviated swelling caused by the CDs, and inhibited the decrease of mitochondrial membrane potential caused by CDs. Furthermore, the protein coronas reduced cellular reactive oxygen species production and alleviated the consumption of glutathione by the CDs, thus protecting the cells from damage. This finding provided valuable information about protein coronas in ameliorating cytotoxicity.

Effect of co-administration of Acori Tatarinowii Rhizoma volatile oil on pharmacokinetic fate of xanthotoxol, oxypeucedanin hydrate, and byakangelicin from Angelicae Dahuricae Radix in rat

A combination of Angelicae Dahuricae Radix and Acori Tatarinowii Rhizoma has been widely used as the herb pair in traditional Chinese medicine to treat stroke, migraine, and epilepsy. However, the underlying synergistic mechanism of the herb pair remains unknown. This study was aimed at investigating the effects of Acori Tatarinowii Rhizoma volatile oil on the pharmacokinetic parameters of xanthotoxol, oxypeucedanin hydrate, and byakangelicin from Angelicae Dahuricae Radix in rat, and in vitro absorption behavior of the three compounds using rat everted gut sac, in situ single-pass intestinal perfusion, and Caco-2 cell monolayer models. The pharmacokinetic study exhibited clear changes in the key pharmacokinetic parameters of the three main coumarins through co-administering with Acori Tatarinowii Rhizoma volatile oil (50 mg/kg), the area under curve and the maximum plasma concentration of xanthotoxol increased 1.36 and 1.31 times; the area under curve, the maximum plasma concentration, mean residence time, half-life of elimination, and the time to reach peak concentration of oxypeucedanin hydrate increased by 1.35, 1.18, 1.24, 1.19 and 1.49 times, respectively; the area under curve, mean residence time, half-life of elimination, and time to reach peak concentration of byakangelicin climbed 1.29, 1.27, 1.37, and 1.28 times, respectively. The three coumarin components were absorbed well in the jejunum and ileum in the intestinal perfusion model, when co-administered with Acori Tatarinowii Rhizoma volatile oil (100 μg/mL). The in vivo and in vitro experiments showed good relevance and consistency. The results demonstrated that the three coumarin compounds from Angelicae Dahuricae Radix were absorbed through the active transportation, and Acori Tatarinowii Rhizoma volatile oil could promote the intestinal absorption and transport of these compounds by inhibiting P-glycoprotein (P-gp)-mediated efflux.

Elevated system exposures of baicalin after combinatory oral administration of rhein and baicalin: Mainly related to breast cancer resistance protein (ABCG2), not UDP-glucuronosyltransferases

ETHNOPHARMACOLOGICAL RELEVANCE

A traditional Chinese medicine (TCM) prescription follows the principle of compatibility (peiwu) to achieve the fundamental purpose: to increase efficacy and reduce toxicity. Rhei rhizoma, commonly known as Chinese rhubarb, is the most frequently used herb with Radix Scutellariaee. This classic fixed compatibility is considered for heat-clearing, qi regulation and detoxifying to gain better efficacy and reduce cytotoxicity with respect to unilateral medicine. With this in mind, we propose it is highly promising to find ingredients in rhubarb to increase the bioavailability of baicalin.

AIM OF STUDY

In the present study, effect of rhien on pharmacokinetic profile of baicalin in rat plasma was investigated, and the underlying mechanisms were partly dissected through intestinal absorption, metabolism and biliary excretion with in vivo, in vitro and in situ assays.

MATERIALS AND METHODS

Pharmacokinetic analysis in rats was first performed to provide a general overview of the in vivo exposure of baicalin and rhein after co-administration, while the biliary excretion study provided insight to the effect of rhein on the transport of baicalin from hepatocytes to bile. In vitro incubation and inhibition studies in human/rat liver microsome and human/rat intestinal S9 fraction were conducted to elucidate the role of uridine diphosphate-glucuronosyltransferases (UGTs) on the hepatic and intestinal metabolism of baicalein (the aglycone of baicalin), and to determine whether rhein can affect the UGT-mediated glucuronidation of baicalein. In situ intestinal perfusion study was designed to investigate the effect of rhein on intestinal absorption of baicalin, and breast cancer resistance protein (BCRP) inhibitor was co-perfused as positive control to demonstrate the role of the efflux transporter, while BCRP-MDCK II cell(Madin-Daby canine kidney cell) model was used as an in vitro approach to further confirm the conclusion.

RESULTS

The AUC and C_max of baicalin were increased to 189.93% and 305.73%, respectively, and the clearance of baicalin was significantly decreased from 4.17 ± 2.40 to 1.65 ± 0.79 L/h/kg following oral co-administration of rhein. The AUC of baicalin was markedly increased and the biliary clearance was significantly decreased when baicalin and rhein were co-administered intravenously. The effect of rhein on the glucuronidation of baicalein in various subcellular fractions was examined, and it was found that rhein did not affect the UGT-mediated glucuronidation of baicalein. Results of in situ intestinal perfusion revealed that co-perfusion with Ko143 (a potent BCRP inhibitor) or rhein significantly reduced the cumulative excretion amount of baicalin, from 9.27 ± 2.79 to 2.80 ± 0.97 or 4.84 ± 0.60 nM, respectively. Additionally, the efflux ratio P_app(BL-AP)/P_app(AP-BL) of baicalin in BCRP-MDCK II was decreased significantly in the presence of rhein or Ko143, which meant rhein could inhibit the BCRP-mediated efflux transport of baicalin.

CONCLUSIONS

These results indicated that rhein can increase the bioavailability of baicalin by inhibiting BCRP-mediated efflux transport of baicalin in enterocytes and hepatocytes rather than by affecting the activity of UGT enzyme.

Fabrication of Fine Puerarin Nanocrystals by Box-Behnken Design to Enhance Intestinal Absorption

Puerarin is widely used as a therapeutic agent to cardiovascular diseases in clinics in China through intravenous administration, which could elicit adverse drug reactions caused by cosolvents, hindering its application in clinics. Therefore, the development of oral dosage is urgently needed. In our previous studies, we proved that the bioavailability of puerarin increased as particle sizes of nanocrystals decreased; however, we have not optimized the best process parameters for nanocrystals. In this study, we aim to fabricate fine nanocrystals (with smallest particle size) by Box-Behnken design and study the intestinal permeability of puerarin and its nanocrystals via employing everted gut sac model and in situ perfusion model. The results showed that the Box-Behnken design could be used to optimize the producing parameters of puerarin nanocrystals, and the particle sizes of fine nanocrystals were about 20 nm. Results of everted gut sacs showed that the polyvinylpyrrolidone (PVP) and verapamil had no influence on the absorption of puerarin and nanocrystals, and the nanocrystals could increase the P_app of puerarin for 2.2-, 2.9-, and 2.9-folds, respectively, in duodenum, jejunum, and ileum. Enhanced Ka and Peff were observed on the nanocrystal group, compared with puerarin, and PVP and verapamil had no influence on the absorption of nanocrystals, while the absorption of puerarin was influenced by P-gp efflux. Combining the results mentioned above, we can conclude that the Box-Behnken design benefits the optimization for preparation of nanocrystals, and the nanocrystals could enhance the intestinal absorption of puerarin by enhanced permeability and inhibited P-gp efflux.

Enhanced oral bioavailability of valsartan in rats using a supersaturable self-microemulsifying drug delivery system with P-glycoprotein inhibitors

Valsartan (VST) is a poorly water-soluble drug and a P-glycoprotein (P-gp) substrate. To enhance the dissolution and oral absorption of VST, a novel supersaturable self-microemulsifying drug delivery system (Su-SMEDDS) was formulated. Based on the previously reported Su-SMEDDS composed of Capmul^® MCM (oil), Tween^® 20 (T20; surfactant), Transcutol^® P (cosurfactant), and Poloxamer 407 (supersaturating agent), P-gp inhibitory surfactants including Tween^® 80 (T80) and Cremophor^® EL (CR) were newly introduced to replace T20. All Su-SMEDDS formulations had a droplet size of <200 nm and showed rapid (>90% within 5 min) and pH-independent dissolution characteristics. The effective permeability coefficient (P_eff) in rat jejunum was obtained using an in situ single-pass intestinal perfusion study: P_eff values of Su-SMEDDS-T20, Su-SMEDDS-T80, and Su-SMEDDS-CR were 2.3, 4.1, and 3.4 times greater, respectively, than that of the VST solution. After oral administration of various formulations to rats (equivalent dose of VST 10 mg/kg), plasma drug levels were measured by liquid chromatography-tandem mass spectrometry. The relative bioavailabilities of Su-SMEDDS-T20, Su-SMEDDS-T80, and Su-SMEDDS-CR were 262%, 470%, and 458%, respectively, compared with the VST suspension. Thus, we propose that the Su-SMEDDS-T80 formulation is a good candidate for improving the oral absorption of poorly water-soluble and P-gp substrate drugs such as VST.

Surface stabilized atorvastatin nanocrystals with improved bioavailability, safety and antihyperlipidemic potential

Atorvastatin, a favored option for hyperlipidemia exhibits the problem of poor gastric solubility and low absolute bioavailability (12%) along with higher pre-systemic clearance (>80%). Therefore, to circumvent these limitations, atorvastatin nanocrystals were prepared using poloxamer-188 as stabilizer via high pressure homogenization technique followed by lyophilization. Various variables like drug to poloxamer-188 ratio, homogenization cycle, homogenization pressure, type and concentration of cryoprotectant were optimized to achieve uniform nanosized crystals with good dispersibility. Solid state characterization by ATR-FTIR and DSC revealed no incompatible physicochemical interaction between drug and excipients in formulation while DSC and PXRD collectively corroborated the reduced crystallinity of drug in nanocrystals. Size analysis and SEM confirmed nanometric size range of nanocrystals (225.43 ± 24.36 nm). Substantial improvement in gastric solubility (~40 folds) and dissolution rate of drug in nanocrystals was observed. Pharmacokinetic study in wistar rats revealed significant improvement in oral bioavailability (~2.66 folds) with atorvastatin nanocrystals compared to pure drug. Furthermore, reduction in serum total lipid cholesterol, LDL and triglyceride content justified the effectiveness of formulation at 50% less dose of atorvastatin along with improved plasma safety profile in comparison of pure drug. In conclusion, atorvastatin nanocrystals are safe and efficacious drug delivery system confirming potent competence in treatment of hyperlipidemic conditions with ease of scalability for commercialization.

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.

Preparation and in vitro/in vivo evaluation of azilsartan osmotic pump tablets based on the preformulation investigation

The objective of this study was to design and evaluate azilsartan osmotic pump tablets. Preformulation properties of azilsartan were investigated for formulation design. Azilsartan osmotic pump tablets were prepared by incorporation of drug in the core and subsequent coating with cellulose acetate and polyethylene glycol 4000 as semi-permeable membrane, then drilled an orifice at the center of one side. The influence of different cores, compositions of semipermeable membrane and orifice diameter on azilsartan release were evaluated. The formulation of core tablet was optimized by orthogonal design and the release profiles of various formulations were evaluated by similarity factor (f₂). The optimal formulation achieved to deliver azilsartan at an approximate zero-order up to 14 h. The pharmacokinetic study was performed in beagle dogs. The azilsartan osmotic pump tablets exhibited less fluctuation in blood concentration and higher bioavailability compared to immediate-release tablets. Moreover, there was a good correlation between the in vitro dissolution and in vivo absorption of the tablets. In summary, azilsartan osmotic pump tablets presented controlled release in vitro, high bioavailability in vivo and a good in vitro-in vivo correlation.

Enhanced dissolution/caco-2 permeability, pharmacokinetic and pharmacodynamic performance of re-dispersible eprosartan mesylate nanopowder

Eprosartan mesylate is an angiotensin receptor blocker which suffers from extremely poor bioavailability owing to its poor solubility and poor permeability. The rationale of the present work was to design the drug delivery system capable of overcoming these constraints. Nanoformulation of eprosartan mesylate was developed using ultrasonic wave-assisted liquid-antisolvent technique. Nanoformulation was further freeze dried with the addition of 1% of mannitol resulting in formation of re-dispersible EPM nanopowder. To prove our proof of principle, the re-dispersed nanopowder with z-average particle size 165.2 ± 1.8 nm was evaluated enormously for in-vitro dissolution behaviour and permeability assay through Caco-2 cell model. In-vitro dissolution study was performed at pH 1.2, pH 4.5 and pH 6.8. Result demonstrates enhanced dissolution from EPM nanopowder with negligible pH dependence. Transport studies accomplished using validated Caco-2 based cell model showed 11-fold enhanced apparent permeability of redispersed nanopowder when compared to pure EPM and corresponding physical mixture (p < 0.0001). In-vivo study reveals, exceptionally strong variations in plasma concentration of EPM through nanopowder (62 mg/kg) formulation when compared with physical mixture and pure EPM (62 mg/kg) group. Moreover, study manifests that 5-fold lower dose (12.4 mg/kg) of developed formulation yields higher exposure (4600 ± 36 ng·mL^-1·h) than pure EPM (2349 ± 34 ng·mL^-1·h) and corresponding physical mixture (2456 ± 49 ng·mL^-1·h) at therapeutic dose (62 mg/kg). Further, L-NAME induced hypertensive model was undertaken to investigate effect of reduced dose of EPM nanopowder on systolic blood pressure, biochemical analysis and histopathology of heart. Results revealed pronounced antihypertensive potential of re-dispersed EPM nanopowder at 5-fold lower dose (12.4 mg/kg). In conclusion, our study indicates that nanopowder delivery might be the promising approach for providing enhanced oral bioavailability at lower dose.

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.

Long-term oral administration of Exendin-4 to control type 2 diabetes in a rat model

Exendin-4 is a glucagon-like peptide-1 (GLP-1) receptor agonist and potent insulinotropic agent for type 2 diabetes patients; however, its therapeutic utility is limited due to the frequent injections required. Long-acting agonists reduce the number of injections, but they can compromise potency. In this study, chondroitin sulfate-g-glycocholic acid-coated and Exendin-4 (Ex-4)-loaded liposomes (EL-CSG) were prepared for oral administration of Ex-4. The Ex-4 loading efficiency was 77% and the loading content in the nanoparticles was 1 wt-%. In rat models, a single oral dose (200 μg/kg) of EL-CSG showed a relative oral bioavailability of 19.5%, compared with subcutaneous administration (20 μg/kg), and sustained pharmacokinetics for up to 72 h. The overall long-term pharmacodynamic effects, assessed by hemoglobin A1c (HbA1c), body weight, and blood lipid concentrations, of daily oral EL-CSG (300 μg/kg) for four weeks were equivalent to or better than daily subcutaneous injections of free Ex-4 solution (20 μg/kg).

Hydrolysis and Transport Characteristics of Tyrosol Acyl Esters in Rat Intestine

Lipophenols such as palmitoyl esters of green-tea polyphenols (GTP) have been allowed for use as food additives for oxidation control. However, their digestive absorption remains unexplored. In this paper, the hydrolysis and transport characteristics of tyrosol acyl esters (TYr-Es) with various fatty acids (C12:0, C14:0, C16:0, C18:0, C18:1, and C18:2) were evaluated using the everted-rat-gut-sac model for the first time. HPLC-UV measurements demonstrated that TYr-Es were hydrolyzed to TYr, which contributed significantly to TYr transport across the sacs. The hydrolysis and transport rates correlated negatively with the chain lengths of their lipid moieties but showed a positive correlation with the degree of unsaturation. In general, all TYr-Es exhibited sustained-release behavior; therefore, the production of TYr-Es may serve as a useful way to prolong the duration of action and further improve the bioactivities of TYr.

Oral Nanoparticles Exhibit Specific High-Efficiency Intestinal Uptake and Lymphatic Transport

Herein, we describe a simple and promising nanoparticle oral delivery phenomenon and propose pathways for oral nanoparticle absorption from the gastrointestinal tract (GIT), combining apical sodium-dependent bile acid transporter-mediated cellular uptake and chylomicron transport pathways. This strategy is proven to employ bile-acid-conjugated, solid fluorescent probe nanoparticles (100 nm diameter) to exclude any potential artifacts and instability issues in observing transport pathways and measuring oral bioavailability. The results of the in vitro studies showed that there is no interference from bile acid and no simultaneous uptake of nanoparticles and dextran. The probe nanoparticle exhibited a significantly enhanced average oral bioavailability (47%) with sustained absorption in rats. Particle-size- and dose-dependent oral bioavailability was observed for oral nanoparticle dosing up to 20 mg/kg. The probe nanoparticles appear to be transported to systemic circulation via the gut lymphatic system. Thus, we propose a pathway for oral nanoparticle absorption from the GIT, combining apical bile acid transporter-mediated cellular uptake and chylomicron transport pathways.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.