Gas chromatography/negative chemical ionization mass spectrometry of transfluthrin in rat plasma and brain.

RATIONALE: Transfluthrin is a relatively non-toxic rapid-acting synthetic pyrethroid insecticide. It is widely used in household and hygiene products. A sensitive and accurate bioanalytical method is required for quantification of its concentration in plasma and its potential target organ, the brain for studies to assess its health effects and toxicokinetics in mammals. METHODS: The samples were prepared by liquid-liquid extraction. Gas chromatography mass spectrometry (GC/MS) analysis was performed for the determination of transfluthrin in biological samples with an overall method run time of 15 min. Transfluthrin was quantified using selected-ion monitoring (SIM) in the negative chemical ionization (NCI) mode. Chromatographic separation was achieved using a Zebron® ZB5-MS GC column operating with 1 mL/min constant flow helium. Cis-Permethrin was used as the internal standard. RESULTS: The method was validated to be precise and accurate within the linear range of 1.0-400.0 ng/mL in plasma and 4.0-400.0 ng/mL in brain homogenate, based on a 100 µL sample volume for both matrices. This method was applied to samples following administration of a 10 mg/kg oral dose to male adult rats. The plasma concentrations were observed to be 11.70 ± 5.69 ng/mL and brain concentrations 12.09 ± 3.15 ng/g when measured 2 h post-dose. CONCLUSIONS: A rapid GC/NCI-MS method was demonstrated to be sensitive, specific, precise and accurate for the quantification of transfluthrin in rat plasma and brain. The optimized method was successfully used to quantify the rat plasma and brain concentrations of transfluthrin 2 h after the oral dosing of Sprague-Dawley rats.

Plasma Drug Concentrations of Orally Administered Rosuvastatin in Hispaniolan Amazon Parrots (Amazona ventralis).

Atherosclerotic diseases are common in pet psittacine birds, in particular Amazon parrots. While hypercholesterolemia and dyslipidemia have not definitely been associated with increased susceptibility to atherosclerosis in parrots, these are important and well-known risk factors in humans. Therefore statin drugs such as rosuvastatin constitute the mainstay of human treatment of dyslipidemia and the prevention of atherosclerosis. No pharmacologic studies have been performed in psittacine birds despite the high prevalence of atherosclerosis in captivity. Thirteen Hispaniolan Amazon parrots were used to test a single oral dose of 10 mg/kg of rosuvastatin with blood sampling performed according to a balanced incomplete block design over 36 hours. Because low plasma concentrations were produced in the first study, a subsequent pilot study using a dose of 25 mg/kg in 2 Amazon parrots was performed. Most plasma samples for the 10 mg/kg dose and all samples for the 25 mg/kg dose had rosuvastatin concentration below the limits of quantitation. For the 10 mg/kg study, the median peak plasma concentration and time to peak plasma concentration were 0.032 µg/mL and 2 hours, respectively. Our results indicate that rosuvastatin does not appear suitable in Amazon parrots as compounded and used at the dose in this study. Pharmacodynamic studies investigating lipid-lowering effects of statins rather than pharmacokinetic studies may be more practical and cost effective in future studies to screen for a statin with more ideal properties for potential use in psittacine dyslipidemia and atherosclerotic diseases.

Evaluation of a potential transporter-mediated drug interaction between rosuvastatin and pradigastat, a novel DGAT-1 inhibitor.

OBJECTIVE: An in vitro drugdrug interaction (DDI) study was performed to assess the potential for pradigastat to inhibit breast cancer resistance protein (BCRP), organic anion-transporting polypeptide (OATP), and organic anion transporter 3 (OAT3) transport activities. To understand the relevance of these in vitro findings, a clinical pharmacokinetic DDI study using rosuvastatin as a BCRP, OATP, and OAT3 probe substrate was conducted. METHODS: The study used cell lines that stably expressed or over-expressed the respective transporters. The clinical study was an open-label, single sequence study where subjects (n = 36) received pradigastat (100 mg once daily x 3 days thereafter 40 mg once daily) and rosuvastatin (10 mg once daily), alone and in combination. RESULTS: Pradigastat inhibited BCRP-mediated efflux activity in a dose-dependent fashion in a BCRP over-expressing human ovarian cancer cell line with an IC(50) value of 5 µM. Similarly, pradigastat inhibited OATP1B1, OATP1B3 (estradiol 17ß glucuronide transport), and OAT3 (estrone 3 sulfate transport) activity in a concentrationdependent manner with estimated IC(50) values of 1.66 ± 0.95 µM, 3.34 ± 0.64 µM, and 0.973 ± 0.11 µM, respectively. In the presence of steady state pradigastat concentrations, AUC(τ, ss) of rosuvastatin was unchanged and its Cmax,ss decreased by 14% (5.30 and 4.61 ng/mL when administered alone and coadministered with pradigastat, respectively). Pradigastat AUC(τ, ss) and C(max, ss) were unchanged when coadministered with rosuvastatin at steady state. Both rosuvastatin and pradigastat were well tolerated. CONCLUSION: These data indicate no clinically relevant pharmacokinetic interaction between pradigastat and rosuvastatin.

Interaction of novel platelet-increasing agent eltrombopag with rosuvastatin via breast cancer resistance protein in humans.

Eltrombopag (ELT), an orally available thrombopoietin receptor agonist, is a substrate of organic anion transporting polypeptide 1B1 (OATP1B1), and coadministration of ELT increases the plasma concentration of rosuvastatin in humans. Since the pharmacokinetic mechanism(s) of the interaction is unknown, the present study aimed to clarify the drug interaction potential of ELT at transporters. The OATP1B1-mediated uptake of ELT was inhibited by several therapeutic agents used to treat lifestyle diseases. Among them, rosuvastatin was a potent inhibitor with an IC(50) of 0.05 µM, which corresponds to one-seventh of the calculated maximum unbound rosuvastatin concentration at the inlet to the liver. Nevertheless, a simulation study using a physiologically based pharmacokinetic model predicted that the effect of rosuvastatin on the pharmacokinetic profile of ELT in vivo would be minimal. On the other hand, ELT potently inhibited uptake of rosuvastatin by OATP1B1 and human hepatocytes, with an IC(50) of 0.1 µM. However, the results of the simulation study indicated that inhibition of OATP1B1 by ELT can only partially explain the clinically observed interaction with rosuvastatin. ELT also inhibited transcellular transport of rosuvastatin in MDCKII cells stably expressing breast cancer resistance protein (BCRP), and was found to be a substrate of BCRP. The interaction of ELT with rosuvastatin can be almost quantitatively explained on the assumption that intestinal secretion of rosuvastatin is essentially completely inhibited by ELT. These results suggest that BCRP in small intestine may be the major target for interaction between ELT and rosuvastatin in humans.

A mechanistic framework for in vitro-in vivo extrapolation of liver membrane transporters: prediction of drug-drug interaction between rosuvastatin and cyclosporine.

BACKGROUND AND OBJECTIVES: The interplay between liver metabolising enzymes and transporters is a complex process involving system-related parameters such as liver blood perfusion as well as drug attributes including protein and lipid binding, ionisation, relative magnitude of passive and active permeation. Metabolism- and/or transporter-mediated drug-drug interactions (mDDIs and tDDIs) add to the complexity of this interplay. Thus, gaining meaningful insight into the impact of each element on the disposition of a drug and accurately predicting drug-drug interactions becomes very challenging. To address this, an in vitro-in vivo extrapolation (IVIVE)-linked mechanistic physiologically based pharmacokinetic (PBPK) framework for modelling liver transporters and their interplay with liver metabolising enzymes has been developed and implemented within the Simcyp Simulator(®). METHODS: In this article an IVIVE technique for liver transporters is described and a full-body PBPK model is developed. Passive and active (saturable) transport at both liver sinusoidal and canalicular membranes are accounted for and the impact of binding and ionisation processes is considered. The model also accommodates tDDIs involving inhibition of multiple transporters. Integrating prior in vitro information on the metabolism and transporter kinetics of rosuvastatin (organic-anion transporting polypeptides OATP1B1, OAT1B3 and OATP2B1, sodium-dependent taurocholate co-transporting polypeptide [NTCP] and breast cancer resistance protein [BCRP]) with one clinical dataset, the PBPK model was used to simulate the drug disposition of rosuvastatin for 11 reported studies that had not been used for development of the rosuvastatin model. RESULTS: The simulated area under the plasma concentration-time curve (AUC), maximum concentration (C max) and the time to reach C max (t max) values of rosuvastatin over the dose range of 10-80 mg, were within 2-fold of the observed data. Subsequently, the validated model was used to investigate the impact of coadministration of cyclosporine (ciclosporin), an inhibitor of OATPs, BCRP and NTCP, on the exposure of rosuvastatin in healthy volunteers. CONCLUSION: The results show the utility of the model to integrate a wide range of in vitro and in vivo data and simulate the outcome of clinical studies, with implications for their design.

Pharmacokinetics of cobicistat boosted-elvitegravir administered in combination with rosuvastatin.

Statins are commonly used medications by HIV-1 patients. Elvitegravir/cobicistat/emtricitabine/tenofovir DF is a single tablet regimen for the treatment of HIV. The pharmacokinetic interaction between cobicistat-boosted elvitegravir (EVG/co) and rosuvastatin was evaluated. Breast cancer resistance protein (BCRP) and organic anion transporting polypeptide (OATP) 1B1 and 1B3 inhibition were assessed in vitro. Healthy subjects (N = 12) received a single dose of rosuvastatin 10 mg alone and in combination with EVG/co. Intensive pharmacokinetic sampling was conducted and safety was assessed throughout the study. Rosuvastatin pharmacokinetic exposure parameters were evaluated using 90% confidence intervals (CI) of the geometric mean ratio (GMR) of the test (combination) versus reference (rosuvastatin alone) using equivalence boundaries of 70-143% for AUCinf and 70-175% for Cmax . Elvitegravir and cobicistat inhibited BCRP and OATP in vitro, emtricitabine and TDF did not. Clinically, study treatments were well tolerated, with adverse events generally mild. Upon coadministration, rosuvastatin plasma concentrations increased (Cmax 89% higher), while AUCinf changes were modest (38% higher) and clinically nonrelevant, potentially driven by moderate inhibition of intestinal efflux by BCRP, and/or hepatic uptake by OATPs by EVG/co. Elvitegravir and cobicistat pharmacokinetics were comparable to historical data. Rosuvastatin may be coadministered with EVG/COBI/FTC/TDF without dose adjustment.

Opposite regulation of hepatic breast cancer resistance protein in type 1 and 2 diabetes mellitus.

Previous studies on diabetes have reported controversial results with regard to transporters in liver. The present study aimed to explore changes in hepatic breast cancer resistance protein (BCRP) expression and functions, as well as the possible underlying mechanisms, in type 2 diabetic patients, type 1 (streptozotocin-induced), and type 2 (Goto Kakizaki) diabetic rats. Protein and mRNA levels of human (h) and rat (r) BCRP were investigated using Western blot and quantitative polymerase chain reaction analyses. Functions of liver rBCRP were evaluated using rosuvastatin. Sandwich cultured rat hepatocytes (SCRH) were cultured with d-glucose, insulin, or oleic acid for 72 h, and rBCRP mRNA was detected. The effect of oleic acid on rBCRP function in SCRH was also investigated using rosuvastatin. Results showed that liver rBCRP mRNA levels decreased to 20% in type 1 diabetic rats, whereas that in diabetic patients and GK rats significantly increased threefold and twentyfold, respectively. No changes were observed in h/rBCRP protein levels of type 2 diabetic patients and GK rats. The functions of rBCRP significantly declined in type 1 diabetic rats but showed no significant changes in GK rats. The data from SCRH indicated that d-glucose decreased rBCRP mRNA level to 60%. Oleic acid increased rBCRP mRNA in SCRH by approximately eightfold but decreased rBCRP function to 50%. Therefore, h/rBCRP expression and functions were oppositely regulated in type 1 and type 2 diabetes mellitus subjects. Alternations in d-glucose, insulin, and free fatty acid levels in plasma might contribute to the changes in h/rBCRP expression and functions.

Effects of vercirnon on the activity of CYP3A4, CYP2C19 and CYP2C8 enzymes and BCRP and OATP1B1 transporters using probe substrates.

PURPOSE: Vercirnon is a CCR9 chemokine receptor antagonist being developed for the treatment of Crohn's disease. As a variety of concomitant medications are often required for the treatment of Crohn's disease, it is important to characterise the drug interaction profile of vercirnon. To confirm the results of previous in vitro inhibition studies, this study assessed the in vivo effect of vercirnon on the activity of cytochrome P450 enzymes (CYP3A4, CYP2C19 and CYP2C8) and drug transport proteins (BCRP and OATP1B1) using probe substrates. METHODS: This was an open-label, single-sequence, repeat-dose study conducted in 24 healthy adult subjects. On days 1-4, subjects received probe substrates (midazolam, pioglitazone, omeprazole and rosuvastatin; in that order), followed by administration of vercirnon 500 mg twice daily (BID) on days 5-14. On days 11-14, in addition to vercirnon 500 mg BID, subjects also received probe substrates as on days 1-4. Blood samples were collected for pharmacokinetic analysis of probe substrates, vercirnon and two of its metabolites. RESULTS: Geometric least-squares mean ratios (90 % confidence interval) of area under the concentration-time curve from time zero to infinity for probe administered with vercirnon (test) compared with probe alone (reference) for midazolam, pioglitazone, omeprazole and rosuvastatin were 0.92 (0.85, 0.99), 1.01 (0.95, 1.07), 0.99 (0.76,1.31) and 0.98 (0.88, 1.09), respectively. CONCLUSIONS: Co-administration of probe substrates midazolam, pioglitazone, omeprazole, and rosuvastatin following repeat dosing of vercirnon 500 mg BID demonstrated vercirnon had no clinically significant effect on CYP3A4, CYP2C8, CYP2C19 enzyme activity or BCRP or OATP1B1 transporter activity.

Hepatic basolateral efflux contributes significantly to rosuvastatin disposition II: characterization of hepatic elimination by basolateral, biliary, and metabolic clearance pathways in rat isolated perfused liver.

Basolateral efflux clearance (CLBL) contributes significantly to rosuvastatin (RSV) elimination in sandwich-cultured hepatocytes (SCH). The contribution of CLBL to RSV hepatic elimination was determined in single-pass isolated perfused livers (IPLs) from wild-type (WT) and multidrug resistance-associated protein 2 (Mrp2)-deficient (TR(-)) rats in the absence and presence of the P-glycoprotein and breast cancer resistance protein (Bcrp) inhibitor, elacridar (GF120918); clearance values were compared with SCH. RSV biliary clearance (CLBile) was ablated almost completely by GF120918 in TR(-) IPLs, confirming that Mrp2 and Bcrp primarily are responsible for RSV CLBile. RSV appearance in outflow perfusate was attributed primarily to CLBL, which was impaired in TR(-) IPLs. CLBL was ≈ 6-fold greater than CLBile in the linear range in WT IPLs in the absence of GF120918. Recovery of unchanged RSV in liver tissue increased in TR(-) compared with WT (≈ 25 versus 6% of the administered dose) due to impaired CLBL and CLBile. RSV pentanoic acid, identified by high-resolution liquid chromatography-tandem mass spectroscopy, comprised ≈ 40% of total liver content and ≈ 16% of the administered dose in TR(-) livers at the end of perfusion, compared with ≈ 30 and 3% in WT livers, consistent with impaired RSV excretion and "shunting" to the metabolic pathway. In vitro-ex vivo extrapolation between WT SCH and IPLs (without GF120918) revealed that uptake clearance and CLBL were 4.2- and 6.4-fold lower, respectively, in rat SCH compared with IPLs; CLBile translated almost directly (1.1-fold). The present IPL data confirmed the significant role of CLBL in RSV hepatic elimination, and demonstrated that both CLBL and CLBile influence RSV hepatic and systemic exposure.

Effects of polymorphisms in ABCG2, SLCO1B1, SLC10A1 and CYP2C9/19 on plasma concentrations of rosuvastatin and lipid response in Chinese patients.

AIM: This study examined whether the ABCG2 421C>A polymorphism and variants in other genes potentially related to the pharmacokinetics of rosuvastatin influenced the plasma concentration of rosuvastatin in Chinese patients with hypercholesterolemia. PATIENTS & METHODS: Overnight fasting blood samples were collected from 291 patients who had received a rosuvastatin 10 mg night-time dose for at least 4 weeks. Plasma concentrations of rosuvastatin and N-desmethyl rosuvastatin were quantified using liquid chromatography tandem mass spectrometry. RESULTS: In subjects with the ABCG2 421AA genotype (n = 39), the mean plasma concentrations of rosuvastatin and its metabolite were 63 and 41% greater than the values in those with the 421CA genotype (n = 108) and 120 and 99% greater than in those with the 421CC genotype (n = 129). The plasma concentrations of rosuvastatin were associated (r = -0.194; p = 0.001) with the percentage reduction in low-density lipoprotein cholesterol with rosuvastatin, but the association was not significant after adjusting for the ABCG2 421C>A polymorphism. The SLCO1B1 521T>C polymorphism was associated with increased plasma concentrations of rosuvastatin and impaired N-demethylation of rosuvastatin, but had no impact on its lipid-lowering effect. Polymorphisms in CYP2C9, CYP2C19 and SLC10A1 had minimal effects. CONCLUSION: These findings suggest that the increased plasma concentrations of rosuvastatin in Chinese patients are associated with increased lipid-lowering effects and lower doses of rosuvastatin should be effective in subjects with the ABCG2 421C>A variant.

Clinical and pharmacogenetic predictors of circulating atorvastatin and rosuvastatin concentrations in routine clinical care.

BACKGROUND: A barrier to statin therapy is myopathy associated with elevated systemic drug exposure. Our objective was to examine the association between clinical and pharmacogenetic variables and statin concentrations in patients. METHODS AND RESULTS: In total, 299 patients taking atorvastatin or rosuvastatin were prospectively recruited at an outpatient referral center. The contribution of clinical variables and transporter gene polymorphisms to statin concentration was assessed using multiple linear regression. We observed 45-fold variation in statin concentration among patients taking the same dose. After adjustment for sex, age, body mass index, ethnicity, dose, and time from last dose, SLCO1B1 c.521T>C (P<0.001) and ABCG2 c.421C>A (P<0.01) were important to rosuvastatin concentration (adjusted R(2)=0.56 for the final model). Atorvastatin concentration was associated with SLCO1B1 c.388A>G (P<0.01) and c.521T>C (P<0.05) and 4ß-hydroxycholesterol, a CYP3A activity marker (adjusted R(2)=0.47). A second cohort of 579 patients from primary and specialty care databases were retrospectively genotyped. In this cohort, genotypes associated with statin concentration were not differently distributed among dosing groups, implying providers had not yet optimized each patient's risk-benefit ratio. Nearly 50% of patients in routine practice taking the highest doses were predicted to have statin concentrations greater than the 90th percentile. CONCLUSIONS: Interindividual variability in statin exposure in patients is associated with uptake and efflux transporter polymorphisms. An algorithm incorporating genomic and clinical variables to avoid high atorvastatin and rosuvastatin levels is described; further study will determine whether this approach reduces incidence of statin myopathy.

RP-LC simultaneous quantitation of co-administered drugs for (non-insulin dependent) diabetic mellitus induced dyslipidemia in active pharmaceutical ingredient, pharmaceutical formulations and human serum with UV-detector.

BACKGROUND: Rapid, efficient and accurate RP-HPLC-UV method for the simultaneous determination and quality control of active pharmaceutical ingredient (API), pharmaceutical formulations and human serum containing drugs as rosuvastatin together with metformin, glimepiride and gliquidone has been proposed. METHODS: The chromatographic system comprised mobile phase of methanol:water 90:10 v/v; pH adjusted to 3.0 with o-phosphoric acid, at 1 ml/min through Prepacked Purospher Star C18 (5 µm, 25×0.46 cm) column with UV detection at isosbestic point 231 nm. RESULTS: The method showed good linearity in the range 0.25-25 µg/ml for metformin and 0.5-50 µg/ml for rosuvastatin, glimepiride and gliquidone with correlation co-efficient ≥ 0.998; (precision %RSD<2) for all drugs in API, formulations and human serum. The recovery of all drugs was 98.9-101.91% in API and formulations and 99.92-102.08% in human serum. The sensitivity of method increased when drugs were analyzed after programming the detector at their individual λmax where their LODs shifted down to 5, 3, 10 and 9 ng/ml from 10, 17, 15 and 14 ng/ml when calculated at their isosbestic point respectively at least concentration 0.125 µg/ml for metformin and 0.25 µg/ml for rosuvastatin, glimepiride and gliquidone with correlation co-efficient ≥ 0.998 in each case. CONCLUSIONS: The proposed drugs can be analyzed by this method for routine analysis and clinical studies with sensitivity at nanoscale with small sample volume.

Enhancement of human oral bioavailability and in vitro antitumor activity of rosuvastatin via spray dried self-nanoemulsifying drug delivery system.

The purpose of this study was to develop spray dried self-nanoemulsifying drug delivery system (SNEDDS) tablets of rosuvastatin using mannitol as a carrier. SNEDDS were prepared using Capryol 90, poloxamer 407 and Transcutol P or triacetin as oil, surfactant and cosurfactants, respectively. The prepared systems were characterized and their cytotoxicity was evaluated using Caco-2 cell lines. A comparative bioavailability study was performed in human volunteers relative to the conventional commercial product. Results showed better self-nanoemulsifying ability of systems containing triacetin compared to Transcutol P. SNEDDS formed uni-modal nanoemulsion droplet size distributions with droplet size less than 50 nm and polydispersity index values ranging from 0.127 to 0.275. The solubilizing capacity of rosuvastatin was affected by both surfactant and cosurfactant concentrations. Upon spray drying, systems prepared using Transcutol P tended to be soft and tacky and were sticking to the walls of the dryer. The redispersion of rosuvastatin from solid SNEDDS was very fast (100% within 5 minutes). Optimized SNEDDS prepared with triacetin were safe with no cytotoxic effect on Caco-2 cells. The anticancer effect of rosuvastatin was enhanced when incorporated in SNEDDS (IC50 value decreased from 4 to 3 microg/ml) due to the increase in penetration of SNEDDS inside the cells. The relative bioavailability for SNEDDS tablets compared to the commercial tablets was 167%. The effective solubilization, penetration and enhancement in bioavailability of SNEDDS tablets proves their potential as a safe, and effective drug delivery system for poorly-soluble drugs.

Metabolism of bis(4-fluorobenzyl)trisulfide and its formation of hemoglobin adduct in rat erythrocytes.

Bis(4-fluorobenzyl)trisulfide (BFBTS) is a promising new antitumor agent under investigation. It was metabolized rapidly in vivo in rat, but the metabolic fate and primary site of metabolism have not been clarified. In this study, we investigated the role of blood in the metabolism of BFBTS and compared the BFBTS metabolic potencies in whole blood, plasma, and red blood cells (RBCs) in vitro. Three major metabolites of BFBTS [bis(4-fluorobenzyl)disulfide, para-fluorobenzyl-mercaptan, and para-fluorobenzoic acid] were detected in RBCs and whole blood. Significant metabolism of BFBTS was observed in RBCs that were identified as the primary site of BFBTS metabolism. Thiols, including endogenous thiols and hemoglobin, were proven to be the critical factor in BFBTS metabolism. S-Fluorobenzylmercaptocysteine Hb (hemoglobin) adducts were characterized in vitro at BFBTS concentration of 250 µM and higher, whereas such Hb adducts were not detected in RBCs from Sprague-Dawley rats receiving a single intravenous injection of BFBTS at a high dose of 50 mg/kg. Liquid chromatography-tandem mass spectrometry results revealed that adduction induced by BFBTS was prone to take place at Cys125 of globin ß chains. Otherwise, glutathionylation of Hb was also observed that may be attributed to the oxidative effect of BFBTS. In summary, BFBTS was unstable when it met with thiols, and RBCs were the main site of BFBTS metabolism. Hb adducts induced by BFBTS could be detected in vitro at high concentration but not in vivo even at high dose.

Effects of piperine, cinnamic acid and gallic acid on rosuvastatin pharmacokinetics in rats.

The purpose of this study was to investigate the potential pharmacokinetic interactions with natural products (such as piperine (PIP), gallic acid (GA) and cinnamic acid (CA)) and rosuvastatin (RSV) (a specific breast cancer resistance protein, BCRP substrate) in rats. In Caco2 cells, the polarized transport of RSV was effectively inhibited by PIP, CA and GA at concentration of 50 µM. After per oral (p.o.) coadministration of PIP, CA and GA (10 mg/kg) significantly increased intravenous exposure (AUC(last)) of RSV (1 mg/kg) by 73.5%, 62.9% and 53.3% (p < 0.05), respectively than alone group (control). Compared with the control (alone) group, p.o. coadministration of PIP, CA and GA (10 mg/kg) significantly increased the oral exposure (AUC(last)) of RSV (5 mg/kg) by 2.0-fold, 1.83-fold (p < 0.05) and 2.34 -fold (p < 0.05), respectively. Moreover, the cumulative biliary excretion of RSV (5 mg/kg, p.o.) was significantly decreased by 53.3, 33.4 and 39.2% at the end of 8 h after p.o. co-administration of PIP, CA and GA (10 mg/kg), respectively. Taken together, these results indicate that the natural products such as PIP, CA and GA significantly inhibit RSV transport in to bile and increased the plasma exposure (AUC(last)) of RSV.

Disposition of atorvastatin, rosuvastatin, and simvastatin in oatp1b2-/- mice and intraindividual variability in human subjects.

Response to statin therapy is often unpredictable because of variability in metabolism and transport. In the recently created organic anion transporting-polypeptide 1b2 (Oatp1b2/Slco1b2)-null mice, the investigators found significantly lower liver-to-plasma ratios compared with controls for atorvastatin (16.0 ± 5.1 vs 43.5 ± 13.7, P = .002) and rosuvastatin (15.2 ± 3.3 vs 28.4 ± 9.3, P = .03), but not simvastatin (5.2 ± 1.1 vs 6.3 ± 2.9, P = .49), following tail vein injection of 1 mg/kg of each drug. In addition, the investigators examined intraindividual variation in atorvastatin, rosuvastatin, and simvastatin pharmacokinetics in healthy human subjects in a crossover study design. Areas under the plasma concentration-time curve of atorvastatin and simvastatin acid were significantly related (Spearman r = 0.68; P = .035), whereas rosuvastatin profile was not related to atorvastatin or simvastatin exposure. Together, these results in mice and humans demonstrate that predictability of exposure to one statin based on another is dependent on the specific statin pairs and the context in which they are compared.

[Effect of OATP1B1 521T --> C heterogenesis on pharmacokinetic characterstics of rosuvastatin in Chinese volunteers].

This study is to report the effect of OATP1B1 gene mutation in the 521T --> C in Chinese human on the pharmacokinetics of rosuvastatin and guide the reasonable clinical application of rosuvastatin by the feature of genetic polymorphism of OATP1B1. Plasma samples were determined with LC-MS: the analyte and internal standard pitavastatin were both analyzed by MS in the ESI, m/z was 480.0 for rosuvastatin and 420.0 for the IS, separately. Genotyping of OATP1B1 was determined with the method of polymerase chain reaction--amplification refractory mutation system targeted at 40 healthy volunteers and showed that there were 7 subjects with 521T --> C mutant, accounting to 17.5% of total and wild type homozygote accounted to 82.5%. It was found that there were significant differences between OATP1B1 mutation in the 521T --> C and wild type homozygote for rosuvastatin pharmacokinetic process in Chinese human. In contrast to OATP1B1 wild type group, OATP1B1 mutation group's absorption degree increased, elimination process decreased. The OATP1B1 mutation should be noted for guiding the reasonable application of rosuvastatin during its clinical use.

Functional characterization of mouse organic anion transporting peptide 1a4 in the uptake and efflux of drugs across the blood-brain barrier.

This study investigated the role of a multispecific organic anion transporter, Oatp1a4/Slco1a4, in drug transport across the blood-brain barrier. In vitro transport studies using human embryonic kidney 293 cells expressing mouse Oatp1a4 identified the following compounds as Oatp1a4 substrates: pitavastatin (K(m) = 8.3 microM), rosuvastatin (K(m) = 12 microM), pravastatin, taurocholate (K(m) = 40 microM), digoxin, ochratoxin A, and [d-penicillamine(2,5)]-enkephalin. Double immunohistochemical staining of Oatp1a4 with P-glycoprotein (P-gp) or glial fibrillary acidic protein demonstrated that Oatp1a4 signals colocalized with P-gp signals partly but not with glial fibrillary acidic protein, suggesting that Oatp1a4 is expressed in both the luminal and the abluminal membranes of mouse brain capillary endothelial cells. The brain-to-blood transport of pitavastatin, rosuvastatin, pravastatin, and taurocholate after microinjection into the cerebral cortex was significantly decreased in Oatp1a4(-/-) mice compared with that in wild-type mice. The blood-to-brain transport of pitavastatin, rosuvastatin, taurocholate, and ochratoxin A, determined by in situ brain perfusion, was significantly lower in Oatp1a4(-/-) mice than in wild-type mice, whereas transport of pravastatin and [D-penicillamine(2,5)]-enkephalin was unchanged. The blood-to-brain transport of digoxin was significantly lower in Oatp1a4(-/-) mice than in wild-type mice only when P-gp was inhibited by N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918). Taken together, these results show that Oatp1a4 can mediate the brain-to-blood and blood-to-brain transport of its substrate drugs across the blood-brain barrier. The brain-to-plasma ratio of taurocholate, pitavastatin, and rosuvastatin was close to the capillary volume in wild-type mice, and it was not affected by Oatp1a4 dysfunction. Whether Oatp1a4 can deliver drugs from the blood to the brain remains controversial.

Enterohepatic disposition of rosuvastatin in pigs and the impact of concomitant dosing with cyclosporine and gemfibrozil.

The hepatobiliary transport and local disposition of rosuvastatin in pig were investigated, along with the impact of concomitant dosing with two known multiple transport inhibitors; cyclosporine and gemfibrozil. Rosuvastatin (80 mg) was administered as an intrajejunal bolus dose in treatments I, II, and III (TI, TII, and TIII, respectively; n = 6 per treatment). Cyclosporine (300 mg) and gemfibrozil (600 mg) were administered in addition to the rosuvastatin dose in TII and TIII, respectively. Cyclosporine was administered as a 2-h intravenous infusion and gemfibrozil as an intrajejunal bolus dose. In treatment IV (TIV, n = 4) 5.9 mg of rosuvastatin was administered as an intravenous bolus dose. The study was conducted using a pig model, which enabled plasma sampling from the portal (VP), hepatic (VH), and femoral veins and bile from the common hepatic duct. The biliary recoveries of the administered rosuvastatin dose were 9.0 +/- 3.5 and 35.7 +/- 15.6% in TI and TIV, respectively. Rosuvastatin was highly transported into bile as shown by the median AUC(bile)/AUC(VH) ratio in TI of 1770 (1640-11,300). Gemfibrozil did not have an effect on the plasma pharmacokinetics of rosuvastatin, most likely because the unbound inhibitor concentrations did not exceed the reported IC(50) values. However, cyclosporine significantly reduced the hepatic extraction of rosuvastatin (TI, 0.89 +/- 0.06; TII, 0.46 +/- 0.13) and increased the AUC(VP) and AUC(VH) by 1.6- and 9.1-fold, respectively. In addition, the biliary exposure and f(e, bile) were reduced by approximately 50%. The strong effect of cyclosporine was in accordance with inhibition of sinusoidal uptake transporters, such as members of the organic anion-transporting polypeptide family, rather than canalicular transporters.

ABCG2 polymorphism markedly affects the pharmacokinetics of atorvastatin and rosuvastatin.

The ABCG2 c.421C>A single-nucleotide polymorphism (SNP) was determined in 660 healthy Finnish volunteers, of whom 32 participated in a pharmacokinetic crossover study involving the administration of 20 mg atorvastatin and rosuvastatin. The frequency of the c.421A variant allele was 9.5% (95% confidence interval 8.1-11.3%). Subjects with the c.421AA genotype (n = 4) had a 72% larger mean area under the plasma atorvastatin concentration-time curve from time 0 to infinity (AUC(0-infinity)) than individuals with the c.421CC genotype had (n = 16; P = 0.049). In participants with the c.421AA genotype, the rosuvastatin AUC(0-infinity) was 100% greater than in those with c.421CA (n = 12) and 144% greater than in those with the c.421CC genotype. Also, those with the c.421AA genotype showed peak plasma rosuvastatin concentrations 108% higher than those in the c.421CA genotype group and 131% higher than those in the c.421CC genotype group (P < or = 0.01). In MDCKII-ABCG2 cells, atorvastatin transport was increased in the apical direction as compared with vector control cells (transport ratio 1.9 +/- 0.1 vs. 1.1 +/- 0.1). These results indicate that the ABCG2 polymorphism markedly affects the pharmacokinetics of atorvastatin and, even more so, of rosuvastatin-potentially affecting the efficacy and toxicity of statin therapy.