Oral Absorption In Rats Research Articles

Phytic acid enhances the oral absorption of isorhamnetin, quercetin, and kaempferol in total flavones of Hippophae rhamnoides L.

AimTotal flavones of Hippophae rhamnoides L. (TFH) have a clinical use in the treatment of cardiac disease. The pharmacological effects of TFH are attributed to its major flavonoid components, isorhamnetin, kaempferol, and quercetin. However, poor oral bioavailability of these flavonoids limits the clinical applications of TFH. This study explores phytic acid (IP6) enhancement of the oral absorption in rats of isorhamnetin, kaempferol, and quercetin in TFH. MethodsIn vitro Caco-2 cell experiments and in vivo pharmacokinetic studies were performed to investigate the effects of IP6. The aqueous solubility and lipophilicity of isorhamnetin, quercetin, and kaempferol were determined with and without IP6, and mucosal epithelial damage resulting from IP6 addition was evaluated by MTT assays and morphology observations. ResultsThe Papp of isorhamnetin, kaempferol, and quercetin was improved 2.03-, 1.69-, and 2.11-fold in the presence of 333μg/mL of IP6, respectively. Water solubility was increased 22.75-, 15.15-, and 12.86-fold for isorhamnetin, kaempferol, and quercetin, respectively, in the presence of 20mg/mL IP6. The lipophilicity of the three flavonoids was slightly decreased, but their hydrophilicity was increased after the addition of IP6 in the water phase as the logP values of isorhamnetin, kaempferol, and quercetin decreased from 2.38±0.12 to 1.64±0.02, from 2.57±0.20 to 2.01±0.04, and from 2.39±0.12 to 1.15±0.01, respectively. The absorption enhancement ratios were 3.21 for isorhamnetin, 2.98 for kaempferol, and 1.64 for quercetin with co-administration of IP6 (200mg/kg) in rats. In addition, IP6 (200mg/kg, oral) caused neither significant irritation to the rat intestines nor cytotoxicity (400μg/mL) in Caco-2 cells. ConclusionsThe oral bioavailability of isorhamnetin, kaempferol, and quercetin in TFH was enhanced by the co-administration of IP6. The main mechanisms are related to their enhanced aqueous solubility and permeability in the presence of IP6. In summary, IP6 is a potential absorption enhancer for pharmaceutical formulations that is both effective and safe.

Discovery of a Rapidly Metabolized, Long-Acting β2 Adrenergic Receptor Agonist with a Short Onset Time Incorporating a Sulfone Group Suitable for Once-Daily Dosing

A series of novel, potent, and selective human β2 adrenoceptor agonists incorporating a sulfone moiety on the terminal right-hand-side phenyl ring of (R)-salmeterol is presented. Sulfone 10b had salmeterol-like potency and selectivity profile, long duration of action on guinea pig trachea, and longer than salmeterol duration of action in vivo, suitable for once-daily dosing. It had lower than salmeterol oral absorption in rat, lower bioavailability in rat and dog, and a high turnover in human hepatocytes. It was metabolized in human hepatocytes by hydroxylation, oxidation, cleavage, and conjugation; most of the metabolites would be expected to have reduced or no β2 activity. The 4-biphenylsulfonic acid was identified as a crystalline, non-hygroscopic salt of 10b, suitable for inhaled delivery. Furthermore, it was free of any genetic toxicity issues and was considered as a backup to vilanterol.

Novel formulation strategies for enhancing oral delivery of methoxyflavones in Kaempferia parviflora by SMEDDS or complexation with 2-hydroxypropyl-β-cyclodextrin

The Kaempferia parviflora (KP) plant contains several methoxyflavones including 5,7-dimethoxyflavone (DMF), 5,7,4'-trimethoxyflavone (TMF), and 3,5,7,3',4'-pentamethoxyflavone (PMF). Ethanolic extracts of KP have shown various pharmacological effects and have been used as an aphrodisiac, a antimicrobial agent and for the treatment of inflammation, and peptic ulcers. Given its poor water solubility and low oral bioavailability (1-4%), there are limitations to the utilization of KP. Accordingly, self-microemulsifying drug delivery system (SMEDDS) and cyclodextrin (CD) complex formulations were developed to improve the oral absorption of methoxyflavones. Polyoxyethylene castor oil (53.3%), propylene glycol (26.7%), and triglyceride of coconut oil (20%) were combined to form KP-SMEDDS. A complex of 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) and KP was prepared by lyophilization. The developed formulations were then evaluated for their physicochemical properties, in vitro dissolution tests, permeability through Caco-2 cells, and in vivo oral absorption in rats by using PMF, TMF, and DMF as the markers for quantitation. The results showed that KP-SMEDDS and KP-2-HP-β-CD complex improved the dissolution rate of methoxyflavones in both 0.1N HCl and 0.2M PBS pH 6.8 compared to KP dissolved in a solution of propylene glycol, PEG 400, ethanol, and water. KP-SMEDDS and KP-2-HP-β-CD formulations showed about 10- and 3.5-fold greater Papp values of methoxyflavones in Caco-2 cells. The oral bioavailability values of KP-SMEDDS formulations were higher than those of KP (25.38-, 42.00-, and 26.01-fold for PMF, TMF, and DMF, respectively). For the KP-2-HP-β-CD complex, oral bioavailability values were 21.63-, 34.20-, and 22.90-fold greater than those of KP, respectively. Therefore, these two novel formulations, KP-SMEDDS and KP-2-HP-β-CD, were successfully developed to improve the dissolution rate, drug permeability through Caco-2 cells and oral bioavailability of methoxyflavones in KP.

Solid-state dependent dissolution and oral bioavailability of piroxicam in rats

The aim of this study was to gain understanding about the effects of different solid-state forms of a poorly water-soluble piroxicam on drug dissolution and oral bioavailability in rats. Three different solid-state forms of piroxicam were studied: anhydrate I (AH), monohydrate (MH), and amorphous form in solid dispersion (SD). In addition, the effect of a new polymeric excipient Soluplus® (polyvinyl caprolactam–polyvinyl acetate–polyethylene glycol graft copolymer) on oral bioavailability of piroxicam was investigated. Significant differences in the dissolution and oral bioavailability were found between the solid-state forms of piroxicam. Amorphous piroxicam in SD showed the fastest dissolution in vitro and a solid-state transformation to MH in the dissolution medium. Despite the presence of solid-state transformation, SD exhibited the highest rate and extent of oral absorption in rats. Oral bioavailability of other two solid-state forms decreased in the order AH and MH. The use of Soluplus® was found to enhance the dissolution and oral bioavailability of piroxicam in rats. The present study shows the importance of solid-state form selection for oral bioavailability of a poorly water-soluble drug.

Discovery of the First Thumb Pocket 1 NS5B Polymerase Inhibitor (BILB 1941) with Demonstrated Antiviral Activity in Patients Chronically Infected with Genotype 1 Hepatitis C Virus (HCV)

Combinations of direct acting antivirals (DAAs) that have the potential to suppress emergence of resistant virus and that can be used in interferon-sparing regimens represent a preferred option for the treatment of chronic HCV infection. We have discovered allosteric (thumb pocket 1) non-nucleoside inhibitors of HCV NS5B polymerase that inhibit replication in replicon systems. Herein, we report the late-stage optimization of indole-based inhibitors, which began with the identification of a metabolic liability common to many previously reported inhibitors in this series. By use of parallel synthesis techniques, a sparse matrix of inhibitors was generated that provided a collection of inhibitors satisfying potency criteria and displaying improved in vitro ADME profiles. "Cassette" screening for oral absorption in rat provided a short list of potential development candidates. Further evaluation led to the discovery of the first thumb pocket 1 NS5B inhibitor (BILB 1941) that demonstrated antiviral activity in patients chronically infected with genotype 1 HCV.

Deletion ofAbcg2Has Differential Effects on Excretion and Pharmacokinetics of Probe Substrates in Rats

This study was designed to characterize breast cancer resistance protein (Bcrp) knockout Abcg2(-/-) rats and assess the effect of ATP-binding cassette subfamily G member 2 (Abcg2) deletion on the excretion and pharmacokinetic properties of probe substrates. Deletion of the target gene in the Abcg2(-/-) rats was confirmed, whereas gene expression was unaffected for most of the other transporters and metabolizing enzymes. Biliary excretion of nitrofurantoin, sulfasalazine, and compound A [2-(5-methoxy-2-((2-methyl-1,3-benzothiazol-6-yl)amino)-4-pyridinyl)-1,5,6,7-tetrahydro-4H-pyrrolo[3,2-c]pyridin-4-one] accounted for 1.5, 48, and 48% of the dose in the Abcg2(+/+) rats, respectively, whereas it was decreased by 70 to 90% in the Abcg2(-/-) rats. Urinary excretion of nitrofurantoin, a significant elimination pathway, was unaffected in the Abcg2(-/-) rats, whereas renal clearance of sulfasalazine, a minor elimination pathway, was reduced by >90%. Urinary excretion of compound A was minimal. Systemic clearance in the Abcg2(-/-) rats decreased 22, 43 (p<0.05), and 57%, respectively, for nitrofurantoin, sulfasalazine, and compound A administered at 1 mg/kg and 27% for compound A administered at 5 mg/kg. Oral absorption of nitrofurantoin, a compound with high aqueous solubility and good permeability, was not limited by Bcrp. In contrast, the absence of Bcrp led to a 33- and 11-fold increase in oral exposure of sulfasalazine and compound A, respectively. These data show that Bcrp plays a crucial role in biliary excretion of these probe substrates and has differential effects on systemic clearance and oral absorption in rats depending on clearance mechanisms and compound properties. The Abcg2(-/-) rat is a useful model for understanding the role of Bcrp in elimination and oral absorption.

Design and Synthesis of Novel DFG-Out RAF/Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) Inhibitors. 1. Exploration of [5,6]-Fused Bicyclic Scaffolds

To develop RAF/VEGFR2 inhibitors that bind to the inactive DFG-out conformation, we conducted structure-based drug design using the X-ray cocrystal structures of BRAF, starting from an imidazo[1,2-b]pyridazine derivative. We designed various [5,6]-fused bicyclic scaffolds (ring A, 1-6) possessing an anilide group that forms two hydrogen bond interactions with Cys532. Stabilizing the planarity of this anilide and the nitrogen atom on the six-membered ring of the scaffold was critical for enhancing BRAF inhibition. The selected [1,3]thiazolo[5,4-b]pyridine derivative 6d showed potent inhibitory activity in both BRAF and VEGFR2. Solid dispersion formulation of 6d (6d-SD) maximized its oral absorption in rats and showed significant suppression of ERK1/2 phosphorylation in an A375 melanoma xenograft model in rats by single administration. Tumor regression (T/C = -7.0%) in twice-daily repetitive studies at a dose of 50 mg/kg in rats confirmed that 6d is a promising RAF/VEGFR2 inhibitor showing potent anticancer activity.

Revisiting the Rule of Five on the Basis of Pharmacokinetic Data from Rat

Physicochemical requirements for oral absorption: The Rule of Five (Ro5) and an alternative set of less stringent rules were evaluated with a large dataset of oral absorption in rat. A combined classification scheme is proposed in which the Ro5 (green area) is used to identify compounds with good oral absorption, whereas less stringent rules (yellow area) are used to differentiate the remaining compounds into medium and low absorption.

In vitro– in vivo study of CoQ10-loaded lipid nanoparticles in comparison with nanocrystals

The present work described the effect of CoQ10 dissolution characteristics in nanocrystals and lipid nanoparticles (LNs) on its oral absorption in rats. Nanocrystals and LNs were prepared by melt-high pressure homogenization and sucrose monolaurate was used as a stabilizer in all formulations. Witepsol ®W35 and medium-chain triglycerides (MCT) were selected as lipid additives to form LN CoQ10+W35 and LN CoQ10+MCT, respectively. From the results obtained, the particle size of CoQ10 nanocrystals was 285 nm, while it was reduced to 150 nm by mixture with an equal amount of lipid additives due to their lower melting points. In vitro dissolution results indicated that the drug release from two LNs was delayed compared with that from nanocrystals, and LN CoQ10+W35 exhibited the highest drug release over 4 h. Finally, in vivo evaluation demonstrated that the oral absorption of CoQ10 was markedly increased by using nanocrystals and LNs compared with a coarse suspension. A good relationship was found between the in vitro dissolution and in vivo evaluation. The enhanced oral absorption of CoQ10 by nanocrystals and LNs was due to improved dissolution. In conclusion, Witepsol ®W35 was shown to be a better lipid additive for the preparation of LNs to increase the oral absorption of CoQ10.

2-Acyl-tetrahydroisoquinoline-3-carboxylic Acids: Lead Compounds with Triple Actions, Peroxisome Proliferator-Activated Receptor .ALPHA./.GAMMA. Agonist and Protein-Tyrosine Phosphatase 1B Inhibitory Activities

2-Acyl-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and biologically evaluated. (S)-2-(2,4-Hexadienoyl)-7-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14) showed peroxisome proliferator-activated receptor γ (PPARγ) and PPARα agonist activities and protein-tyrosine phosphatase 1B (PTP-1B) inhibitory activities. PPARγ agonist activity of 14 was comparable to that of rosiglitazone, and PTP-1B inhibitory activity was about 10-fold weaker than that of ertiprotafib, a PTP-1B inhibitor. Compound 14 showed high oral absorption in rats and potent hypoglycemic effects in KK-A(y) mice. In conclusion, 14 would be an excellent lead compound for a new type of anti-diabetic drug with triple actions.

Enhancement by adrenaline of ginsenoside Rg1 transport in Caco-2 cells and oral absorption in rats

The purpose of this research was to evaluate the ability of adrenaline (epinephrine) to stimulate the uptake of ginsenoside Rg1 (Rg1) by Caco-2 cells. Rg1 uptake was measured using Caco-2 cell monolayers. The Rg1 uptake medium with adrenaline at different concentrations was added to each well and incubated for different time intervals. Adrenergic antagonists such as phentolamine and propranolol were added to the incubation medium to investigate their effects on Rg1 uptake. The Rg1 concentration in the monolayers was determined by high-performance liquid chromatography. Transport of Rg1 across Caco-2 cells was also studied and an oral bioavailability study of Rg1 was carried out in rats. The incubation medium with adrenaline remarkably increased the amount of Rg1 uptake by Caco-2 cells. Adrenaline-induced Rg1 transport increased in a dose- and time-dependent manner. The effect of adrenergic antagonists on adrenaline-induced uptake of Rg1 was investigated and it was found that the enhancement effect was attenuated by the co-treatment with propranolol but not phentolamine. The transport amount of Rg1 by Caco-2 cells increased in response to 1 mM adrenaline, isoproterenol or salbutamol. In contrast, 1 mM phenylephrine had no effect on Rg1 transport in Caco-2 cells. The effect of adrenaline on the absorption of Rg1 was further investigated in vivo in rats. The co-administration with adrenaline in rats showed that the oral bioavailability was increased remarkably relative to the aqueous solution. The area under the plasma concentration-time curve of Rg1 after co-administration with 1 mM adrenaline was 79.1 +/- 31.04 microg/ml/h compared with 2.81 +/- 1.13 microg/ml/h for its aqueous solution. Adrenaline is effective for the stimulation of intestinal absorption of Rg1 and the enhanced absorption is mediated mainly by the interaction of adrenaline with beta2-adrenoceptors.

Enhancement by adrenaline of ginsenoside Rg1 transport in Caco-2 cells and oral absorption in rats

Objectives The purpose of this research was to evaluate the ability of adrenaline (epinephrine) to stimulate the uptake of ginsenoside Rg1 (Rg1) by Caco-2 cells. Methods Rg1 uptake was measured using Caco-2 cell monolayers. The Rg1 uptake medium with adrenaline at different concentrations was added to each well and incubated for different time intervals. Adrenergic antagonists such as phentolamine and propranolol were added to the incubation medium to investigate their effects on Rg1 uptake. The Rg1 concentration in the monolayers was determined by high-performance liquid chromato-graphy. Transport of Rg1 across Caco-2 cells was also studied and an oral bioavailability study of Rg1 was carried out in rats. Key findings The incubation medium with adrenaline remarkably increased the amount of Rg1 uptake by Caco-2 cells. Adrenaline-induced Rg1 transport increased in a dose- and time-dependent manner. The effect of adrenergic antagonists on adrenaline-induced uptake of Rg1 was investigated and it was found that the enhancement effect was attenuated by the co-treatment with propranolol but not phentolamine. The transport amount of Rg1 by Caco-2 cells increased in response to 1 mM adrenaline, isoproterenol or salbutamol. In contrast, 1 mM phenylephrine had no effect on Rg1 transport in Caco-2 cells. The effect of adrenaline on the absorption of Rg1 was further investigated in vivo in rats. The co-administration with adrenaline in rats showed that the oral bioavailability was increased remarkably relative to the aqueous solution. The area under the plasma concentration-time curve of Rg1 after co-administration with 1 mM adrenaline was 79.1 ± 31.04 μg/ml/h compared with 2.81 ± 1.13 μg/ml/h for its aqueous solution. Conclusions Adrenaline is effective for the stimulation of intestinal absorption of Rg1 and the enhanced absorption is mediated mainly by the interaction of adrenaline with β2-adrenoceptors.

Triterpene based compounds with potent anti-maturation activity against HIV-1

Efforts towards developing orally bioavailable HIV-1 maturation inhibitors starting from betulinic acid 1 are described. SAR resulted in improved potency, physicochemical properties, and enhanced oral absorption in rats.

Permeability evaluation of peptidic HCV protease inhibitors in Caco-2 cells-correlation with in vivo absorption predicted in humans

The permeability of six peptidic hepatitis C virus (HCV) protease inhibitors, with molecular weights ranging from 500 to 780, was examined in the Caco-2 cell system. All six compounds permeated the cells transcellularly; paracellular permeability, evaluated in the Caco-2 cell system by reducing the calcium concentration in the media to increase the pore size of the tight junctions, most likely contributes only minimally to the oral absorption of the compounds. All six compounds were shown to be efflux substrates displaying concentration-dependent saturation of efflux. The efflux could be blocked by cyclosporine A, a specific P-glycoprotein (P-gp) inhibitor, suggesting that P-gp may be the responsible transporter. Oral absorption in rats was calculated using in vivo oral bioavailability and hepatic extraction ratios. Human oral absorption was projected to be similar to that of rats, as reported previously by comparing rat and human absorption values for 23 marketed drugs. Upon comparison of human oral absorption predicted by Caco-2 permeability and by rat pharmacokinetics, we show a better correlation with Caco-2 permeability obtained at higher compound concentrations, where efflux is saturated, than at lower concentrations. The higher concentrations are likely reflecting the lumen concentrations after in vivo oral dosing. The results presented in this study demonstrate that, when tested at relevant compound concentrations, Caco-2 permeability is useful for predicting the oral absorption of peptidic compounds.

In Vivo Effects of Glycyl-Glutamate and Glycyl-Sarcosine on Gabapentin Oral Absorption in Rat

The objective of this study was to evaluate the in vivo consequences of glycyl-glutamate coadministration on gabapentin oral absorption. Rats were administered gabapentin (10 mg/kg plus radiotracer) by gastric gavage, in the absence and presence of dipeptides, and by intravenous administration. Serial blood samples were obtained over 6 h and the pharmacokinetics of gabapentin were determined by noncompartmental analysis. Glycyl-glutamate coadministration increased the Cmax of gabapentin by 86% as compared to gabapentin alone. In agreement, the oral absorption of gabapentin, relative to the intravenous dose, was 79% after glycyl-glutamate loading but only 47% when drug was administered alone. However, when glycyl-sarcosine was added to the orally administered admixture of gabapentin plus glycyl-glutamate, values for Cmax and AUC(0-6 h) reverted back to that of control. In contrast, the tmax and terminal half-life of gabapentin did not change after oral dosing for all treatments. These findings are unique in demonstrating that under physiologic, in vivo conditions, the luminal presence of glycyl-glutamate could dramatically enhance the Cmax and AUC(0-6 h) of gabapentin. The results are consistent with previous in situ intestinal perfusion studies in rat, and establish a functional interaction between the activities of PEPT1 and amino acid exchangers.

Efforts toward oral bioavailability in factor VIIa inhibitors

Efforts toward developing orally bioavailable factor VIIa inhibitors starting from parenteral lead compound 1 are described. SAR resulted in improved physicochemical properties, leading to enhanced oral absorption in rat.

Ubidecarenone nanoemulsified composite systems

The nanoemulsified composite (NEC ™) delivery system is a patented technology based on the incorporation of a double microemulsion into microporous carrier. This approach was applied on the very water insoluble ubidecarenone drug. The resulting composite powder showed good technological properties such as flowability; also good stability was evidentiated, with size of the nano-droplets released from the systems maintained equal to the starting size also after a long storage. Furthermore very good biopharmaceutical properties were originated, with water solubility concentrations up to 50-fold higher than pure ubidecarenone and oral absorption in rats up to three-fold greater than standard commercial products in terms of plasma levels and AUC.

Venoruton metabolites: pharmacological activity and kinetics

Objective: This study was undertaken to further elucidate the mechanism of action of the phlebotonic drug Venoruton®, which is a standardized mixture of hydroxyethylrutosides (HR). Methods: First, its oral absorption in rats was compared with that of hydroxyethylquercetins (HQ), which are the hydrolysed aglycones of HR. Second, the pharmacological activity of the major HR metabolites in humans, mono-3′-hydroxyethylquercetin (mono-3′HQ) and a mixture with mono-4′HQ, were further evaluated in vitro. Results: Time to reach the maximal plasma concentration of its marker metabolite mono-4′HQ was significantly shorter after HQ than after HR administration, with an eightfold higher maximal concentration. The rapid absorption of HQ and the increased plasma levels confirm the theory that rutosides need to be hydrolysed by the intestinal microflora prior to absorption. Mono-3′HQ and, even more so, the mixture with mono-4′HQ inhibited xanthine oxidase, an enzyme responsible for the formation of reactive oxygen species, at concentrations comparable to those found in human plasma. The metabolites also inhibited the formation of superoxide radicals induced by the respiratory burst of activated HL-60 neutrophils. Both HR metabolites decreased the degree of cell death of human umbilical vein endothelial cells that were exposed to hypoxia/reoxygenation conditions, probably by scavenging destructive superoxide radicals. Conclusions: These results demonstrated new pharmacological activities, which contribute to the understanding of the mechanisms of action of HR in chronic venous insufficiency.

Prodrugs of 9‐Benzyl‐8‐hydroxy‐2‐(2‐hydroxyethylthio)adenine: Potent Interferon Inducing Agents in Monkeys.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The influence of enaminones on the transport and oral bioavailability of P-glycoprotein substrate therapeutic agents

Objective: The enaminones have shown high P-gp affinity and may act as P-gp modulators. This study investigated the potential inhibition of the enaminones on paclitaxel efflux in vitro compared to cyclosporin A, a known P-gp inhibitor, and the effectiveness of select enaminones on paclitaxel oral absorption in rats. Methods: Caco-2 transport of [ 14 C ]paclitaxel was evaluated in presence of various enaminones at 10 −5 M. Concentration–effect (10 −10 M to 10 −4 M) profiles for the enaminones, DM27 and/or DM40, with paclitaxel and cyclosporin A were determined. Male Sprague–Dawley (250–275 g) rats were orally administered either [ 14 C ]paclitaxel (30 μCi/kg) or [ 14 C ]paclitaxel/DM27 (7 mg/kg) and blood samples were collected. Paclitaxel brain concentrations were measured. Results: Papp (A–B) of [ 14 C ]paclitaxel, with DM27 and DM40 at 10 −5 M, was significantly ( P<0.05) higher versus control. DM27 produced a 360% and a 139% increase in Papp (A–B)Paclitaxel and Papp (A–B)Cyclosporin, respectively. DM40 displayed a 131% increase in Papp (A–B)Paclitaxel whereas cyclosporin A produced a 213% increase in Papp (A–B)Paclitaxel. Rats in the DM27 group displayed large Vd ss/ F values (23.35 liters/kg versus 14.62 liters/kg) and lower AUC (5.47 μg/ml min versus 8.74 μg/ml min) versus control. However, significantly higher levels (2.25-fold) of paclitaxel were observed in the brains of the DM27 group. Conclusion: This study presents the enaminones as promising P-gp inhibitors with comparable potency to other P-gp inhibitors. Furthermore, the enaminones may improve conventional therapy when used in combination with P-gp substrate drugs.