The effect of quercetin on the pharmacokinetics of chlorzoxazone, a CYP2E1 substrate, in healthy subjects.

PURPOSE: Previous in vitro studies have demonstrated that quercetin inhibits CYP2E1 enzyme, but there are no available data to indicate that quercetin inhibits CYP2E1 enzyme in humans. The purpose of the present study was to assess the effect of quercetin on CYP2E1 enzyme activity in healthy subjects using chlorzoxazone (CHZ) as a CYP2E1 substrate. METHODS: An open-label, two-period, sequential study was conducted in 12 healthy subjects. A single dose of CHZ 250 mg was given to subjects during control phase and after treatment phases. Quercetin at a dose of 500 mg was given to subjects twice daily for a period of 10 days. The blood samples were collected at predetermined time intervals after CHZ dosing and analyzed to determine the concentrations of CHZ and 6-hydroxychlorzoxazone (6-OHCHZ). RESULTS: Treatment with quercetin significantly enhanced the maximum plasma concentration (C max), area under the curve (AUC), and half-life (t 1/2) by 47.8, 69.3, and 36.4%, respectively, while significantly decreased the elimination rate constant (k el) and apparent oral clearance (CL/F) of CHZ by 25.1 and 41.6%, respectively, in comparison with the control. On the other hand, C max and AUC of 6-OHCHZ were decreased by 30.1 and 32.6%, respectively, after quercetin treatment when compared to control. In addition, geometric mean ratios and 90% confidence intervals for C max and AUC of CHZ and 6-OHCHZ were both out of the no-effect boundaries of 0.80-1.25, which indicates a significant pharmacokinetic interaction present between CHZ and quercetin. Furthermore, treatment with quercetin significantly decreased the metabolic ratios of C max and AUC by 57.1 and 60.1%, respectively, as compared to control suggesting that reduced formation of CHZ to 6-OHCHZ. CONCLUSIONS: The results suggest that altered pharmacokinetics of CHZ might be attributed to quercetin-mediated inhibition of CYP2E1 enzyme. Further, the inhibition of CYP2E1 by quercetin may represent a novel therapeutic approach for minimizing the ethanol-induced CYP2E1 enzyme activity and results in reduced hepatotoxicity of ethanol.

Quercetin nanoparticles alter pharmacokinetics of bromocriptine, reflecting its enhanced inhibitory action on liver and intestinal CYP 3A enzymes in rats.

1. Quercetin is a dietary flavonoid has extremely low water solubility and found to possess CYP3A inhibitory activity. The purpose of the present study was to evaluate the effect of quercetin and quercetin nanoparticles (NQC) on the pharmacokinetics of bromocriptine (BRO) in rats. 2. NQC prepared by antisolvent precipitation method and characterized by SEM and dissolution test. The following methods were used in this study i.e. in vitro liver and intestinal CYP3A microsomal activity and in vitro non-everted sac method. To confirm these findings, an in vivo pharmacokinetic study was also performed. 3. The results indicate that quercetin significantly (p < 0.05) inhibited the CYP3A activity in liver and intestinal microsomes. In non-everted sac study, the intestinal transport and Papp of BRO were significantly increased in NQC and quercetin groups. Furthermore, in vivo study revealed that the increased levels of Cmax and AUC were comparatively high in NQC pretreated group than quercetin group. In addition, pretreatment with quercetin and NQC significantly (p < 0.05) decreased the mean CL/F and Vd/F of BRO. 4. NQC pretreatment might be result in higher plasma levels of quercetin that could inhibit the CYP3A enzyme and enhanced the bioavailability of BRO.

Evaluation of the effect of quercetin treatment on CYP2C9 enzyme activity of diclofenac in healthy human volunteers.

The purpose of present study was to evaluate the effect of quercetin on pharmacokinetics of diclofenac sodium (DIC) in healthy volunteers. The open-label, 2 period, sequential study was conducted in 12 healthy volunteers. DIC 100 mg was administered during control and after quercetin phases. Quercetin 500 mg was administered twice daily for 10 days during quercetin phase. Treatment with quercetin significantly enhanced maximum plasma concentration (Cmax ), area under the curve (AUC0-∞ ), and half life, while significantly decreased elimination rate constant (kel ) and apparent oral clearance (CL/F) of DIC compared with control. On the other hand, Cmax and AUC0-∞ of 4-hydroxydiclofenac (4-OHDIC) were decreased after quercetin treatment. In addition, geometric mean ratios and 90% confidence intervals for Cmax and AUC0-∞ of DIC and 4-OHDIC were both out of the no-effect limits of 0.80-1.25, which indicates a significant pharmacokinetic interaction between quercetin and DIC. Furthermore, quercetin treatment significantly decreased metabolic ratios of Cmax and AUC0-∞ suggesting that reduced formation of DIC to 4-OHDIC. The results suggest that quercetin might have inhibited CYP2C9-mediated metabolism of DIC. Accordingly, caution should be taken when quercetin is used in combination with therapeutic drugs metabolized by CYP2C9, and dose adjustment of CYP2C9 substrates may be necessary.

Enhanced Oral Bioavailability of Domperidone with Piperine in Male Wistar Rats: Involvement of CYP3A1 and P-gp Inhibition.

PURPOSE: Domperidone is a commonly used antiemetic drug. The oral bioavailability of domperidone is very low due to its rapid first pass metabolism in the intestine and liver. Piperine, the main alkaloid present in black pepper has been reported to show inhibitory effects on Cytochrome P-450 (CYP-450) enzymes and P-glycoprotein (P-gp). In the present study we investigated the effect of piperine pretreatment on the intestinal transport and oral bioavailability of domperidone in male Wistar rats. METHODS: The intestinal transport of domperidone was evaluated by an in-vitro non-everted sac method and in-situ single pass intestinal perfusion (SPIP) study. The oral pharmacokinetics of domperidone was evaluated by conducting oral bioavailability study in rats. RESULTS: A statistically significant improvement in apparent permeability (Papp) was observed in rats pretreated with piperine compared to the respective control group. The effective permeability (Peff) of domperidone was increased in the ileum of the piperine treated group. Following pretreatment with piperine, the peak plasma concentration (Cmax) and area under the concentration- time curve (AUC) were significantly increased. A significant decrease in time to reach maximum plasma concentration (Tmax), clearance and elimination rate constant (Kel) was observed in rats pretreated with piperine. CONCLUSIONS: Piperine enhanced the oral bioavailability of domperidone by inhibiting CYP3A1 and P-gp in rats. This observation suggests the possibility that the combination of piperine with other CYP3A4 and P-gp dual substrates may also improve bioavailability. Further clinical studies are recommended to verify this drug interaction in human volunteers and patients. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Enhanced Oral Bioavailability of Diltiazem by the Influence of Gallic Acid and Ellagic Acid in Male Wistar Rats: Involvement of CYP3A and P-gp Inhibition.

The oral bioavailability of diltiazem is very low due to rapid first pass metabolism in liver and intestine. The purpose of the study was to investigate the effect of gallic acid and ellagic acid on intestinal transport and oral bioavailability of diltiazem in rats. The intestinal transport and permeability of diltiazem was evaluated by in vitro non-everted sac method and in situ single pass intestinal perfusion study. The oral pharmacokinetics was evaluated by conducting oral bioavailability study. The intestinal transport and apparent permeability of diltiazem were significantly enhanced in duodenum, jejunum, and ileum of gallic and ellagic acid-treated groups. The effective permeability of diltiazem was significantly enhanced in ileum part of gallic and ellagic acid-treated groups. When compared with control group, the presence of these two phytochemicals significantly enhanced the area under plasma concentration-time curve and the peak plasma concentration of diltiazem (Cmax ). Gallic acid and ellagic acid significantly increased the bioavailability of diltiazem due to the inhibition of both CYP3A-mediated metabolism and P-glycoprotein-mediated efflux in the intestine and/or liver. Based on these results, the clinical experiments are warranted for the confirmation to reduce the dose of diltiazem when concomitantly administered with these phytochemicals. Copyright © 2017 John Wiley & Sons, Ltd.

Brain targeted PLGA nanocarriers alleviating amyloid-Β expression and preserving basal survivin in degenerating mice model.

The chronic systemic administration of d-Galactose in C57BL/6J mice showed a relatively high oxidative stress, amyloid-ß expression and neuronal cell death. Enhanced expression of pyknotic nuclei, caspase-3 and reduced expression of neuronal integrity markers further confirmed the aforesaid insults. However, concomitant treatment with the recombinant protein (SurR9-C84A) and the anti-transferrin receptor antibody conjugated SurR9-C84A (SurR9+TFN) nanocarriers showed a significant improvement in the disease status and neuronal health. The beauty of this study is that the biodegradable Food and Drug Administration (FDA) approved poly(lactic-co-glycolic acid) (PLGA) nanocarriers enhanced the biological half-life and the efficacy of the treatments. The nanocarriers were effective in lowering the amyloid-ß expression, enhancing the neuronal integrity markers and maintaining the basal levels of endogenous survivin that is essential for evading the caspase activation and apoptosis. The current study herein reports for the first time that the brain targeted SurR9-C84A nanocarriers alleviated the d-Galactose induced neuronal insults and has potential for future brain targeted nanomedicine application.

Resveratrol Pretreatment Affects CYP2E1 Activity of Chlorzoxazone in Healthy Human Volunteers.

The purpose of the present study was to investigate the effect of resveratrol (RSV) pretreatment on CYP2E1 enzyme activity and pharmacokinetics of chlorzoxazone (CHZ) in healthy human volunteers. The open-label, two period, sequential study was conducted in 12 healthy human volunteers. A single dose of RSV 500 mg was administered once daily for 10 days during treatment phase. A single dose of CHZ 250 mg was administered during control and after treatment phases under fasting conditions. The blood samples were collected after CHZ dosing at predetermined time intervals and analyzed by HPLC. RSV pretreatment significantly enhanced the maximum plasma concentration (Cmax), area under the curve (AUC) and half life (T1/2) and significantly decreased elimination rate constant (Kel), apparent oral clearance (CL/F) and apparent volume of distribution (Vd/F) of CHZ as compared to that of control. In addition, RSV pretreatment significantly decreased the metabolite to parent (6-OHCHZ/CHZ) ratios of Cmax, AUC and T1/2 and significantly increased the Kel ratio of 6-OHCHZ/CHZ, which indicated the reduced formation of CHZ to 6-OHCHZ. The results suggest that the altered CYP2E1 enzyme activity and pharmacokinetics of CHZ might be attributed to RSV mediated inhibition of CYP2E1 enzyme. Thus, there is a potential pharmacokinetic interaction between RSV and CHZ. The inhibition of CYP2E1 by RSV may provide a novel approach for minimizing the hepatotoxicity of ethanol.

Effect of Resveratrol Treatment on the Pharmacokinetics of Diclofenac in Healthy Human Volunteers.

The purpose of the present study was to assess the effect of resveratrol (RSV) treatment on the pharmacokinetics of diclofenac (DIC) in healthy human volunteers. The open-label, two period, sequential study was conducted in 12 healthy human volunteers. A single dose of RSV 500 mg was administered daily for 10 days during treatment phase. A single dose of DIC 100 mg was administered during control and after treatment phases under fasting conditions. The blood samples were collected after DIC dosing and analyzed by HPLC. Treatment with RSV significantly enhanced maximum plasma concentration (Cmax) (1.73 to 2.91 µg/mL), area under the curve (AUC) (5.05 to 9.95 g h/mL), half life (T1/2) (1.12 to 1.76 h) and significantly decreased elimination rate constant (Kel ) (0.71 to 0.41 h(-1)), apparent oral clearance (CL/F) (14.58 to 6.48 L/h) of DIC as compared to control. The geometric mean ratios for Cmax, AUC, T1/2, Kel and CL/F of DIC were 1.75, 2.12, 1.65, 0.61 and 0.47, respectively were outside the limits of 0.8-1.25, which indicates clinically significant interaction between DIC and RSV. The results suggest that the altered pharmacokinetics of DIC might be attributed to RSV mediated inhibition of CYP2C9 enzyme. Therefore, combination therapy of DIC along with RSV may represent a novel approach to reduce dosage and results in reduced gastrointestinal side effects of DIC.

Evaluation of the effect of curcumin capsules on glyburide therapy in patients with type-2 diabetes mellitus.

This study aimed to assess the possible beneficial effects of curcumin capsules as lipid-lowering effects and as a permeability glycoprotein (P-gp) inhibitor on the pharmacokinetics and pharmacodynamics of glyburide and as a P-gp substrate with glyburide in patients with type-2 diabetes mellitus. Open-label, randomized control trial was carried out for 11 days on eight type-2 diabetic patients on glyburide therapy. On the first day of the study, following the administration of 5 mg of glyburide, blood samples were collected from the patients at various time intervals ranging from 0.5 to 24 h. Blood sampling was repeated on the 11th day of the study, after treating the patients with curcumin for ten consecutive days. Glyburide concentrations changed at the second hour, Cmax was unchanged, the glucose levels were decreased, Area Under first Movement Curre (AUMC) was increased, and no patient has experienced the hypoglycaemia. The low-density lipoprotein, very-low-density lipoprotein and triglycerides were decreased significantly, and the high-density lipoprotein content increased. The co-administration of curcumin capsules with glyburide may be beneficial to the patients in better glycaemic control. The lipid lowering and antidiabetic properties of the curcumin show as a potential future drug molecule.

Novel Indole Derivative as the First P-glycoprotein Inhibitor from the Skin of Indian Toad (Bufo melanostictus)

Objectives: To study the inhibitory effect of novel indole derivative (NID) from Indian toad skin (Bufo melanostictus) on permeability glycoprotein (P-gp). Materials and Methods: Dried Indian toad skin was used to isolate NID with column chromatography, and its structure was elucidated by infrared spectra, 13C nuclear magnetic resonance (NMR), 1H NMR spectra, and liquid chromatography-mass spectrometry. Female Wistar rats were used to determine LD50, in vitro permeability studies were done with the intestinal sac method, and in vivo pharmacokinetic studies were carried out to prove the P-gp inhibition using the rat model. Results: The NID has shown increased clear permeability Papp (x10-6 cm/sec) significantly (p<0.001) from 1.04±0.11 to 2.90±0.08 in ileum 1.44±0.14 to 3.92±0.13 in jejunum this in vitro results confirmed that P-gp inhibited, this was further confirmed by in vivo studies in in vivo studies observed increased oral bioavailability of digoxin (DIG) significantly in NID treated groups from 3.26±0.25 to 7.47±0.18 ng/mL, the volume of distribution decreased from 232.56±64.59 to 86.57±7.04 L/kg. Area under the curve increased from 37.89±1.13 to 64.62±0.70 ng/mL/hr. This demonstrates NID increased the oral bioavailability of DIG significantly. Conclusion: Many compounds were isolated from the Indian toad skin. This NID was not reported earlier. Results demonstrate NID increased the oral bioavailability of DIG significantly. The isolated NID from Indian toad skin proved as a potent P-gp inhibitor in both in vitro and in vivo studies, and further studies are needed to develop as a possible new drug candidate.

Improved neuroprotective effect of resveratrol nanoparticles as evinced by abrogation of rotenone-induced behavioral deficits and oxidative and mitochondrial dysfunctions in rat model of Parkinson's disease.

The objective of the present study was to evaluate the protective effect of resveratrol nanoparticles (NRSV) against rotenone-induced neurodegeneration in rats. NRSV were prepared by temperature-controlled antisolvent precipitation method and characterized for its particle size, shape, and dissolution properties. Moreover, NRSV effects compared with the free resveratrol (RSV). Animals were divided into four groups: (I) control, (II) rotenone (2 mg/kg s.c.), (III) RSV (40 mg/kg, p.o.) + rotenone, and (IV) NRSV (40 mg/kg, p.o.) + rotenone. Animals received treatments 30 min before rotenone administration for a period of 35 days. Behavioral quantifications were done using rota rod test and rearing behavior after 24 h of last dose. Animals were euthanized, and mid brains were isolated for the estimation of tricarboxylic acid cycle enzymes, oxidative measures (lipid peroxidation (LPO), glutathione (GSH), and catalase), and complex-I activity. In addition, histopathological studies were also performed. Our results showed that chronic rotenone treatment causes motor deficits, decreased rearing behavior, mitochondrial dysfunction, and oxidative stress. Furthermore, histological analysis demonstrated neuronal degeneration in rotenone-treated rats. An important finding of the present study was NRSV showed comparatively better efficacy than the RSV treatment in attenuating the rotenone-induced Parkinson's like behavioral alterations, biochemical and histological changes, oxidative stress, and mitochondrial dysfunction in rats.

Modulation of CYP3A enzyme activity by diosmin and its consequence on carbamazepine pharmacokinetics in rats.

Diosmin is a widely used flavonoid for the treatment of varicose veins and hemorrhoids. Epileptic patients with hemorrhoids and varicose veins may use diosmin along with carbamazepine (CBZ) therapy, which leads to pharmacokinetic interaction between diosmin and CBZ. Therefore, the present study was performed to evaluate the effect of diosmin on the pharmacokinetics of CBZ in rats. Diosmin-mediated altered CYP3A enzyme activity in human and rat liver microsomes was examined using CYP3A dependent erythromycin N-demethylase assay. Further, an in vivo pharmacokinetic study of oral administered CBZ in rats with and without diosmin pretreatment was performed. The CYP3A enzyme activity in human and rat liver microsomes was significantly (p < 0.05) decreased by diosmin when compared to control. Pretreatment with diosmin significantly (p < 0.05) enhanced maximum plasma concentration (C max), area under the curve (AUC), and half life (t 1/2), while significantly (p < 0.05) decreased elimination rate constant (k el) and apparent oral clearance (CL/F) of CBZ as compared to control rats. On the other hand, C max, AUC, and t 1/2 of carbamazepine 10, 11-epoxide (CBZE) were significantly (p < 0.05) decreased after diosmin pretreatment. Furthermore, diosmin pretreatment significantly (p < 0.05) decreased metabolic ratios of C max and AUC when compared to control, suggesting reduced formation of CBZ to CBZE. The results suggest that diosmin pretreatment might have inhibited CYP3A-mediated metabolism of CBZ. Accordingly, caution should be taken when diosmin is used in combination with therapeutic drugs metabolized by CYP3A enzyme in addition to CBZ.

Corrigendum: Topical Ophthalmic Formulation of Trichostatin A and SurR9-C84A for Quick Recovery Post-alkali Burn of Corneal Haze.

[This corrects the article DOI: 10.3389/fphar.2017.00223.].

Enhancement of oral bioavailability of rivastigmine with quercetin nanoparticles by inhibiting CYP3A4 and esterases.

BACKGROUND: Quercetin is a well-known flavonoid, has pharmacokinetic interaction with ester drugs due to its capability of esterase inhibition in the gut and liver. However, the interaction between quercetin nanoparticles (NQC) and rivastigmine has not been reported. Hence, the present study was performed to evaluate the effect of quercetin alone and its nanoparticles on the pharmacokinetics of rivastigmine in rats. METHODS: NQC prepared by antisolvent precipitation method. The influence of quercetin on the pharmacokinetics of rivastigmine was evaluated by following methods i.e. in vitro inhibitory effect on esterase enzyme in rat liver microsomes and in vitro assessment of CYP3A activity using erythromycin-N-demethylase (EMD) assay. To confirm these findings, an in vivo pharmacokinetic study of orally administered rivastigmine in rats with quercetin and NQC pretreatments was performed. RESULTS: The size of NQC was observed below 300nm. Quercetin significantly (p<0.05) inhibited the esterase-mediated metabolism of rivastigmine. In in vitro assessment of CYP3A activity model the erythromycin-N-demethylation (EMD) levels in quercetin treated group were significantly reduced (p<0.05). Cmax, AUC0-t and AUC0- ∞ of rivastigmine were found to be increased in quercetin and NQC pretreated groups. Further, the CL/F and Vd/F of rivastigmine were significantly decreased. CONCLUSIONS: The results revealed that enhanced bioavailability of rivastigmine might be caused by the combination of their effects due to CYP3A and esterase inhibition, Therefore, concomitant administration of NQC influences the bioavailability of rivastigmine and also has synergetic effect in the treatment of Alzheimer's disease.

Topical Ophthalmic Formulation of Trichostatin A and SurR9-C84A for Quick Recovery Post-alkali Burn of Corneal Haze.

Alkali burn injury is a true ocular emergency of the conjunctiva and cornea that requires immediate precision. Lack of an immediate therapy can lead to a substantial damage in the ocular surface and anterior segment further causing visual impairment and disfigurement. We explored the regenerative capability of dominant negative survivin protein (SurR9-C84A) and histone deacetylase inhibitor trichostatin-A (TSA) in vivo, in a rat alkali burn model. A topical insult in rat eyes with NaOH led to degradation of the conjunctival and corneal epithelium. The integrity of the conjunctival and corneal tissue was increased by TSA and SurR9-C84A by improving the clathrin and claudin expressions. Wound healing was initiated by an increase in TGF-beta-1 and, increased endogenous survivin which inhibited apoptosis post-TSA and SurR9-C84A treatments. Protein expressions of fibronectin and alpha-integrin 5 were found to increase promoting corneal integrity. The cytokine analysis confirmed increased expressions of IL-1beta, IL-6, IL-12, IL-13, IFN-gamma, TNF-alpha, GMCSF, Rantes, and MMP-2 in injured cornea, which were found to be significantly downregulated by the combined treatment of SurR9-C84A and TSA. The ocular and systemic pharmacokinetic (PK) parameters were measured post-topical ocular administration of TSA and SurR9-C84A. The SurR9-C84A and TSA sustained relatively longer in the cornea, conjunctiva, and aqueous humor than in the tear fluid and plasma. Our results confirmed that a combination of TSA with SurR9-C8A worked in synergy and showed a promising healing and anti-inflammatory effect in a very short time against alkali burn. Therefore, a combination of TSA and SurR9-C84A can fulfill the need for an immediate response to wound healing in alkali burnt cornea. We also synthesized ultra-small chitosan nanoparticles (USC-NPs) targeted with alpha-SMA antibodies that can be used for delivery of TSA and SurR9-C84A specifically to the ocular burn site.

Enhanced oral bioavailability of metoprolol with gallic acid and ellagic acid in male Wistar rats: involvement of CYP2D6 inhibition.

BACKGROUND: Cytochrome P450-2D6 (CYP2D6), a member of the CYP450 mixed function oxidase system, is an important CYP isoform with regard to herbal-drug interactions and is responsible for the metabolism of nearly 25% of drugs. Until now, studies on the effects of various phytochemicals on CYP2D6 activity in vivo have been very rare. Gallic acid and ellagic acid are natural polyphenols which are widely distributed in fruits and medicinal plants. In the present study, the effects of gallic acid and ellagic acid pretreatment on intestinal transport and oral bioavailability of metoprolol were investigated. METHODS: The intestinal transport of metoprolol was assessed by conducting an in situ single pass intestinal perfusion (SPIP) study. The bioavailability study was conducted to evaluate the pharmacokinetic parameters of orally administered metoprolol in rats. RESULTS: After pretreatment with gallic acid and ellagic acid, no significant change in effective permeability of metoprolol was observed at the ileum part of rat intestine. A significant improvement in the peak plasma concentration (Cmax) and area under the serum concentration-time profile (AUC) and decrease in clearance were observed in rats pretreated with gallic acid and ellagic acid. CONCLUSIONS: Gallic acid and ellagic acid significantly enhanced the oral bioavailability of metoprolol by inhibiting CYP2D6-mediated metabolism in the rat liver. Hence, adverse herbal-drug interactions may result with concomitant ingestion of gallic acid and ellagic acid supplements and drugs that are CYP2D6 substrates. The clinical assessment of these interactions should be further investigated in human volunteers.

Effect of resveratrol on the pharmacokinetics of fexofenadine in rats: Involvement of P-glycoprotein inhibition.

BACKGROUND: Resveratrol (RSV) is a natural occurring antioxidant has been found to possess P-glycoprotein (P-gp) inhibition activity in vitro and in vivo, which may have the potential to cause drug-phytochemical interactions. The purpose of the present study was to evaluate the effect of RSV on the pharmacokinetics of fexofenadine (FEX), P-gp substrate in rats. METHODS: A mechanistic evaluation was undertaken using in vitro non-everted sac and in situ intestinal perfusion studies to determine the FEX intestinal transport and permeability. These results were confirmed by an in vivo pharmacokinetic study of oral administered FEX (10mg/kg) in rats. RESULTS: The intestinal transport and apparent permeability (Papp) of FEX were increased significantly in duodenum, jejunum and ileum of RSV and verapamil (VER) pretreated groups when compared to FEX alone group. Similarly absorption rate constant (Ka), fraction absorbed (Fab) and effective permeability (Peff) of FEX were increased significantly in ileum of RSV and VER pretreated groups when compared to FEX alone group. In comparison with FEX alone, RSV pretreatment significantly increased maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC), while there was no significant change was observed in T1/2 and Tmax of FEX. CONCLUSIONS: RSV significantly enhanced the exposure of FEX in rats likely by the inhibition of P-glycoprotein (P-gp) mediated efflux during the intestinal absorption, suggesting that there is a potential pharmacokinetic interaction between RSV and FEX. Therefore, further studies are recommended to evaluate the potential drug-phytochemical interactions in humans.

Detection of antidiabetic activity by crude paratoid gland secretions from common Indian toad (bufomelano stictus).

BACKGROUND: Amphibians have provided a remarkable array of biological active compounds, which are secreted from socalled granular skin glands which serve to protect the amphibians from predators due to its noxious effects on buccal tissue and at least in the case of some peptides, to protect from bacterial (or) protozoan infections. Given the respiratory and antimicrobial functions of amphibian skin, it is likely that some of the novel molecules found in amphibian granular gland secretions might be of use in the treatment of skin and respiratory infections. Secretions from common Indian toad (Bufo melanostictus) a member of Bufonidae family has the history of medicinal use however the anti-diabetic activity is not reported. The present study is aimed to determine whether paratoid gland extract have any influence on the diabetes and the pharmacokinetics and pharmacodynamics of glimepiride (GLM) in normal and diabetic rats. MATERIALS AND METHODS: An aqueous and methanolic extracts of paratoid glandular secretions were prepared, air dried and used to determine the antidiabetic activity in rats. The blood sampling was done at preset time intervals between 0, 0.5, 1, 2, 4, 6, 8 and 12 h, using heparinized capillaries. The blood glucose levels are estimated by glucose oxidase-peroxidase method, and reversed-phase high-performance liquid chromatography is used to determine the pharmacokinetic parameters of GLM using glibenclamide as an internal standard. RESULTS: Both the aqueous and methanolic extracts produced better glycemic control in diabetic rats, and methanolic extract is better than the aqueous extract. Serum concentrations of GLM increased at 2(nd) h, and the percentage glucose reduction is maximal at the 4(th) h with both aqueous and methanolic extracts of paratoid secretions of common Indian toad. CONCLUSIONS: Paratoid gland secretions of the common Indian toad is antidiabetic, in addition it has beneficial effects in combination with GLM. Further, it requires the systematic structure elucidation of the compounds and pharmacokinetic studies to explore the beneficial effects.

Effect of diosmin on the intestinal absorption and pharmacokinetics of fexofenadine in rats.

BACKGROUND: Diosmin is a natural flavone glycoside, a potent P-glycoprotein (P-gp) inhibitor in cultured cells and have the potential to alter the bioavailability of P-gp substrate drugs. However, the interaction between diosmin and fexofenadine is unreported. Hence, the present study was performed to investigate the effect of diosmin on the intestinal absorption and pharmacokinetics of fexofenadine, a P-gp substrate in rats. METHODS: Fexofenadine intestinal transport and permeability were evaluated by in vitro non-everted sac and in situ single pass intestinal perfusion (SPIP) studies. These results were confirmed by an in vivo pharmacokinetic study of oral administered fexofenadine (10mg/kg) in rats. RESULTS: The intestinal transport and apparent permeability (Papp) of fexofenadine were significantly increased in duodenum, jejunum and ileum of diosmin pretreated group as compared with the control. Similarly effective permeability (Peff) of fexofenadine was increased significantly in ileum of diosmin pretreated group as compared with control. In comparison with control, pretreatment with diosmin significantly increased peak plasma concentration (Cmax) and area under the concentration-time curve (AUC), while there was no significant change was observed in half life (T1/2), time to reach peak plasma concentration (Tmax) and elimination rate constant (Kel) of fexofenadine. CONCLUSIONS: Diosmin significantly enhanced the oral bioavailability of fexofenadine by the inhibition of P-gp mediated drug efflux during the intestinal absorption. Co-administration of diosmin with fexofenadine can reduce the dosage and results in reduced side effects of fexofenadine. The clinical relevance of this interaction should be further evaluated in human subjects.