Prediction of the Area under the Curve Using Limited-Point Blood Sampling in a Cocktail Study to Assess Multiple CYP Activities.

A cocktail study is an in vivo evaluation method to assess multiple CYP activities via a single trial and single administration of a cocktail drug that is a combination of multiple CYP substrates. However, multiple blood samples are required to evaluate the pharmacokinetics of a CYP probe drug. A limited-point sampling method is generally beneficial in clinical studies because of the simplified protocol and reduced participant burden. The aim of this study was to evaluate whether a limited-point plasma concentration analysis of CYP substrates in a cocktail drug could predict their area under the curve (AUC). We created prediction models of five CYP substrates (caffeine, losartan, omeprazole, dextromethorphan, and midazolam) using multiple linear regressions from the data of two cocktail studies, and then performed predictability analysis of these models using data derived from data in the co-administration with inducer (rifampicin) and inhibitors (fluvoxamine and cimetidine). For the administration of inhibitors, the AUC prediction accuracy (mean absolute error (MAE)) were <39.5% in Model 1 and <26.2% in Model 2 which were created using 1- and 4-point sampling data. MAE shows larger values in the administration of inducer in compared with the administration of inhibitors. The accuracy of the prediction in Model 2 could be acceptable for screening of inhibitions. MAE for caffeine, dextromethorphan, and midazolam were acceptable in the model that used 4 sampling points from all data. The use of this method could reduce the burden on the subject and make it possible to evaluate each AUC in a minimally invasive manner.

Applications of shun shell column and nanocomposite sorbent for analysis of eleven anti-hypertensive in human plasma.

High-performance liquid chromatography (HPLC) and solid phase micro membrane tip extraction (SPMMTE) methods are developed for the simultaneous analysis of eleven cardiovascular drugs in human plasma. Iron nanoparticles were obtained by the green method, characterized by XRD, FT-IR, TEM, and EDS and utilized in SPMMTE for sample preparation. The mobile phase used was ammonium acetate buffer-methanol-acetonitrile (65:18:17) with a 1.0 mL/min flow rate at 260 nm detection. Column used was Sunshell C18 150 × 4.6 mm, 2.6 µm. The values of k, α, and Rs were ranged from 040 to109.22, 1.20 to 2.67 and 1.0 to 26.18. SPMMTE and HPLC methods were fast, reproducible, precise, robust, economic and rugged for analysis of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan and spironolactone in human plasma. The recoveries (%) of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan, and spironolactone were 91.0, 85.2, 92.3, 90.4, 90.1, 85.6, 86.6, 86.2, 85.1, 86.6, and 85.7, respectively. These results showed that SPMMTE and HPLC methods can be applied to test the described drugs in several matrices.

Evaluation of potential herbal-drug interactions of a standardized propolis extract (EPP-AF®) using an in vivo cocktail approach.

ETHNOPHARMACOLOGICAL RELEVANCE: Propolis has been employed extensively in many cultures since ancient times as antiseptic, wound healing, anti-pyretic and others due to its biological and pharmacological properties, such as immunomodulatory, antitumor, anti-inflammatory, antioxidant, antibacterial, antiviral, antifungal, antiparasite activities. But despite its broad and traditional use, there is little knowledge about its potential interaction with prescription drugs. AIM OF THE STUDY: The main objective of this work was to study the potential herbal-drug interactions (HDIs) of EPP-AF® using an in vivo assay with a cocktail approach. MATERIALS AND METHODS: Subtherapeutic doses of caffeine, losartan, omeprazole, metoprolol, midazolam and fexofenadine were used. Sixteen healthy adult volunteers were investigated before and after exposure to orally administered 125 mg/8 h (375 mg/day) EPP-AF® for 15 days. Pharmacokinetic parameters were calculated based on plasma concentration versus time (AUC) curves. RESULTS: After exposure to EPP-AF®, it was observed decrease in the AUC0-∞ of fexofenadine, caffeine and losartan of approximately 18% (62.20 × 51.00 h.ng/mL), 8% (1085 × 999 h.ng/mL) and 13% (9.01 × 7.86 h.ng/mL), respectively, with all 90% CIs within the equivalence range of 0.80-1.25. On the other hand, omeprazole and midazolam exhibited an increase in AUC0-∞ of, respectively, approximately 18% (18.90 × 22.30 h.ng/mL) and 14% (1.25 × 1.43 h.ng/mL), with the upper bounds of 90% CIs slightly above 1.25. Changes in pharmacokinetics of metoprolol or its metabolite α-hydroxymetoprolol were not statistically significant and their 90% CIs were within the equivalence range of 0.80-1.25. CONCLUSIONS: In conclusion, our study shows that EPP-AF® does not clinically change CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A activities, once, despite statistical significant, the magnitude of the changes in AUC values after EPP-AF® were all below 20% and therefore may be considered safe regarding potential interactions involving these enzymes. Besides, to the best of our knowledge this is the first study to assess potential HDIs with propolis.

Magnetic solid phase extraction with carbon-coated Fe3O4 nanoparticles coupled to HPLC-UV for the simultaneous determination of losartan, carvedilol, and amlodipine besylate in plasma samples.

In this paper, a chemical coprecipitation method was used for the synthesis of Fe3O4 magnetic nanoparticles. The Fe3O4 magnetic nanoparticles were then modified by carbon via a simple hydrothermal method by using glucose. The synthesized Fe3O4 and carbon-coated Fe3O4 (C/Fe3O4) magnetic nanoparticles were characterized by diverse techniques such as XRD, FESEM, EDX, FTIR, and BET. The characterization results were confirmed the formation of the uniformly magnetic nanoparticles and a successful modification of them by carbon. The FTIR spectra confirmed the presence of functional groups on the C/Fe3O4 magnetic nanoparticles surface. The magnetic nanoparticles were used for extraction of losartan, carvedilol, and amlodipine besylate from plasma samples based on magnetic solid phase extraction (MSPE) technique. The effective parameters on extraction efficiency were optimized by multivariate optimization. Under the optimized experimental conditions the MSPE method showed wide linear ranges (1-7500 ng mL-1), low detection limits (0.09-0.69 ng mL-1), good extraction recoveries (56.35-66.43%), and low RSD values (1.6-5.8%). Despite high protein binding of the drugs, the analyses of them were done without protein precipitation. The accuracy was studied by analyses of the spiked plasma samples at different concentrations.

A Validated Ultra-Performance Liquid Chromatography Tandem Triple Quadrupole Mass Spectrometric Method for Fast Determination of Losartan in Rabbit Plasma.

A rapid UPLC-MS-MS method was developed and validated for determination of losartan in rabbit plasma. Protonated adducts of losartan and eprosartan (IS) were monitored in multiple reaction monitoring mode. Molecular masses of daughter species of losartan were m/z 423.19 > 207 and m/z 423.19 > 180; and of eprosartan were m/z 425.11 > 135 and m/z 425.11 > 107. Losartan from plasma samples was extracted by protein precipitation method. The mobile phase comprising water (0.1% formic acid) (A) and acetonitrile (0.1% formic acid) (B) was used in gradient mode. Analytes were eluted on Acquity UPLC®BEH C18 1.7 µm, 2.1 × 50 mm column. Sample run time was 3.0 min. The validation parameters: accuracy, precision and recovery were within recommended limits. Losartan as well as internal standard remains stable in benchtop stability study as well as in post-preparative stability study. Pharmacokinetic parameters such as Cmax (182.79 ± 23.80 ng/mL), Tmax (1.16 ± 0.28 h), AUC0-t (1188.57 ± 404.60 ng h/mL) and Kel (0.0954 ± 0.0140 h-1) of losartan were measured. Method was successfully applied for pharmacokinetic investigation in rabbits and can be used for losartan determination in plasma sample obtained from other animals.

In vivo phenotyping of cytochrome 450 isoforms involved in the metabolism of anti-HIV and anti-tubercular drugs in human using cocktail approach: An LC-MS/MS analysis.

PURPOSE: In vivo phenotyping of CYP isoforms involved in the metabolism of anti-HIV and antitubercular drugs is important to determine therapeutic dose levels in HIV/AIDS-TB coinfections. In this study, we used a cocktail of bupropion, losartan and dapsone for in vivo phenotyping of CYP2B6, CYP2C9 and N-acetyltransferase-2 (NAT2) in plasma. CYP2B6 is the main catalyst of anti-HIV efavirenz, while NAT2 is involved in antitubercular drug isoniazid metabolism. CYP2C9 has a significant association with antitubercular drug-induced reactions. The activity level of these isoforms has a significant bearing on therapeutic dose in rapid and poor metabolizers. METHODS: Briefly, a cocktail of probe drugs was administered to human volunteers and the drugs and metabolites were determined by an inhouse LC-MS/MS method in 250 µl plasma. The mobile phase and drug/metabolite extraction methods were optimized before analysis. Retention time, Cmax and tmax were calculated from the same sample and the values were used for phenotyping the isoforms. RESULTS: Retention time of drugs and metabolites was calculated. The method was sensitive (4.5-8.2 %CV) and no interfering peak was observed in any batch. %Accuracy of the calibrator and QC was 85-115%. %CV of storage stability testing was within FDA approved limits. Cmax and tmax were comparable to the values reported for individual drugs. CONCLUSIONS: This study advocates the use of a cocktail of bupropion, losartan and dapsone for in vivo phenotyping of CYP2B6, CYP2C9 and NAT2, which is important in determining therapeutic dose levels of anti-HIV and anti-TB drugs in HIV/AIDS-TB coinfections.

1H NMR based pharmacometabolomics analysis of metabolic phenotype on predicting metabolism characteristics of losartan in healthy volunteers.

Inter-individual variability in drug metabolism and disposition is common in both preclinical and clinical researches. Losartan and its active metabolite EXP3174 present a high degree of inter-individual differences in blood concentrations that affect drug efficacy and side effect. Pharmacometabolomics has been increasingly applied on predicting the drug responses by analyzing the differences in metabolic profile. A pre-dose metabolic phenotype was investigated to interpret inter-individual variations in the metabolism characteristics of losartan. 1H Nuclear Magnetic Resonance (NMR) spectroscopy-based metabolic profiles were performed on 36 healthy Chinese male volunteers by measuring their pre-dose plasma samples. After oral administration of losartan, the concentrations of losartan and its bioactive metabolite EXP3174 were monitored by liquid chromatography-mass spectrometry (LC-MS). Orthogonal partial least-squares (O-PLS) model was conducted to select potential biomarkers that substantially contributed to the inter-individual variations in the metabolism features via analyzing the ratio of pharmacokinetics (PK) parameters of its metabolite to parent drug. Potential metabolites such as glycine, phosphorylcholine, choline, creatine, creatinine, lactate, citrate, α-glucose, and lipids showed strong correlations with metabolism features of losartan. In addition, the pathway analysis revealed that baseline lipid metabolism, the glycine, serine and threonine pathway, and glycolysis or gluconeogenesis metabolism pathway were significantly associated with the ratio of PK parameters of EXP3174 to losartan. Step-wise multiple linear regression (MLR) was constructed to investigate the potential roles of the selected biomarkers in predicting individualized metabolism characteristics of losartan. These results showed that the pre-dose individual metabolic traits may be a useful approach for characterizing individual differences in losartan metabolism characteristics and therefore for expediting personalized dose-setting in further clinical studies.

Validated determination of losartan and valsartan in human plasma by stir bar sorptive extraction based on acrylate monolithic polymer, liquid chromatographic analysis and experimental design methodology.

In our previous work, a new monolithic coating based on vinylpyrrolidone-ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The formulation of the prepared vinylpyrrolidone-ethylene glycol dimethacrylate monolithic polymer was optimized and the satisfactory quality of prepared coated stir bar was demonstrated. In this work, the prepared stir bar was utilized in combination with ultrasound-assisted liquid desorption, followed by high-performance liquid chromatography with ultraviolet detection for the simultaneous determination of losartan (LOS) and valsartan (VAS) in human plasma samples. In a comparison study, the extraction efficiency of the prepared stir bar was accompanied much higher extraction efficiency than the two commercial stir bars (polydimethylsiloxand and polyacrylate) for both target compounds. In order to improve the desorption efficiency of LOS and VAS, the best values for effective parameters on desorption step were selected systematically. Also, the effective parameters on extraction step were optimized using a Box-Behnken design. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for LOS (24-1000 ng mL-1) and VAS (91-1000 ng mL-1), with correlation coefficients of 0.9998 and 0.9971 and detection limits of 7 and 27 ng mL-1, respectively. The intra- and inter-day recovery ranged from 98 to 117%, and the relative standard deviations were less than 8%. Finally, the proposed technique was successfully applied to the analysis of LOS and VAS at their therapeutic levels in volunteer patient plasma sample. The obtained results were confirmed using liquid chromatography-mass spectrometry. The proposed technique was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of LOS and VLS in biological fluids. The obtained results were demonstrated that the lower selectivity of UV in comparison with MS detection was rectified by appropriate sample preparation through proposed extraction method to eliminate as many interfering compounds as possible.

Green-modified micellar liquid chromatography for isocratic isolation of some cardiovascular drugs with different polarities through experimental design approach.

Bilayer pseudo-stationary phase micellar liquid chromatography (MLC) was developed for simultaneous isocratic isolation of hydrochlorothiazide, as a basic-polar (hydrophilic) cardiovascular drug, as well as triamterene and losartan potassium, as acidic-nonpolar (hydrophobic) cardiovascular drugs. Utilizing a deep eutectic solvent (DES), as a novel green mobile phase additive in combination with acetonitrile (ACN) and acetic acid (ACA), drastically improved the chromatographic behavior of the drugs. Concentration of sodium dodecyl sulphate (SDS), as well as volume percentages of ACN, DES, and ACA were optimized by using a central composite design. The optimal composition of the mobile phase (0.12 mol L-1 SDS, 5% ACN, 4% DES, and 2% ACA) was chosen through the desirability function. The chromatographic peaks of both hydrophilic and hydrophobic drugs, respectively, emerged at high and low retention time values in the shortest total analysis time of 20 min (at a flow rate of 2 mL min-1). Analytical characterization of the developed approach was investigated through Food and Drug Administration (FDA) guidelines. Applicability of the method was evaluated by analysing of human plasma samples which were directly injected into the system.

Prediction of Losartan-Active Carboxylic Acid Metabolite Exposure Following Losartan Administration Using Static and Physiologically Based Pharmacokinetic Models.

The aim of this study was to evaluate a strategy based on static and dynamic physiologically based pharmacokinetic (PBPK) modeling for the prediction of metabolite and parent drug area under the time-concentration curve ratio (AUCm/AUCp) and their PK profiles in humans using in vitro data when active transport processes are involved in disposition. The strategy was applied to losartan and its pharmacologically active metabolite carboxylosartan as test compounds. Hepatobiliary transport including transport-mediated uptake, canilicular and basolateral efflux, and metabolic clearance estimates were obtained from in vitro studies using human liver microsomes and sandwich-cultured hepatocytes. Human renal clearance of carboxylosartan was estimated from dog renal clearance using allometric scaling approach. All clearance mechanisms were mechanistically incorporated in a static model to predict the relative exposure of carboxylosartan versus losartan (AUCm/AUCp). The predicted AUCm/AUCp were consistent with the observed data following intravenous and oral administration of losartan. Moreover, the in vitro parameters were used as initial parameters in PBPK permeability-limited disposition models to predict the concentration-time profiles for both parent and its active metabolite after oral administration of losartan. The PBPK model was able to recover the plasma profiles of both losartan and carboxylosartan, further substantiating the validity of this approach.

The effect of tripterygium glucoside tablet on pharmacokinetics of losartan and its metabolite EXP3174 in rats.

Losartan and tripterygium glucoside tablet (TGT) are often simultaneously used for reducing urine protein excretion in clinic. However, it is unknown whether there is potential herb-drug interaction between losartan and TGT. The aim of this study was to investigate their potential herb-drug interaction, and clarify the mechanism of the effect of TGT on the pharmacokinetics of losartan and its metabolite EXP3174 in rats. The plasma concentrations of losartan and EXP3174 were determined by LC-MS, and the main pharmacokinetic parameters were calculated. The Cmax , t1/2 and AUC(0-t) of losartan became larger after co-administration, while the Cmax and AUC(0-t) of EXP3174 became smaller, suggesting that TGT could influence the pharmacokinetics of losartan and EXP3174. The effects of TGT and its main components on the metabolic rate of losartan were further investigated in rat liver microsomes. Results indicated that TGT and its two main ingredients could decrease the metabolic rate of losartan. Therefore, it was speculated that TGT might increase the plasma concentration of losartan and decrease the concentration of EXP3174 by inhibiting the metabolism of losartan. The results could provide references for clinical medication guidance of losartan and TGT to avoid the occurrence of adverse reactions.

Effects of berberine on the pharmacokinetics of losartan and its metabolite EXP3174 in rats and its mechanism.

CONTEXT: Losartan and berberine (BBR) are often simultaneously used for the treatment of senile diabetic nephropathy in clinics. However, the potential herb-drug interaction between losartan and BBR is unknown. OBJECTIVE: This study investigates the influence of BBR on the pharmacokinetics of losartan and EXP3174, and investigates the effects of BBR on the metabolic stability of losartan. MATERIALS AND METHODS: The pharmacokinetic profiles losartan and EXP3174 of orally administered losartan (10 mg/kg) with and without pretreatment with BBR (20 mg/kg) within 24 h were determined in Sprague-Dawley rats. The inhibitory effects of BBR on the metabolic stability of losartan were investigated using rat liver microsomes. RESULTS: The Cmax (1.26 ± 0.37 versus 1.96 ± 0.45 mg/L) and the AUC(0-t) (8.25 ± 0.89 versus 12.70 ± 1.42 mg h/L) of losartan were significantly (p < 0.05) increased by BBR compared to the control, while the Cmax (0.97 ± 0.15 versus 0.77 ± 0.06 mg/L) of EXP3174 was significantly decreased compared to the control (p < 0.05). The Tmax of losartan was prolonged from 0.41 ± 0.12 to 0.52 ± 0.18 h, but the difference was not significant. However, the Tmax of EXP3174 was decreased significantly (p < 0.05) from 8.14 ± 0.36 to 3.33 ± 0.28 h. The metabolic stability of losartan was increased from 37.4 to 59.6 min. DISCUSSION AND CONCLUSION: We infer that BBR might increase the plasma concentration of losartan and decrease the concentration of EXP3174 through inhibiting the activity of CYP3A4 or CYP2C9.

Effects of salvianolic acid B and tanshinone IIA on the pharmacokinetics of losartan in rats by regulating the activities and expression of CYP3A4 and CYP2C9.

Losartan (LST) is a common chemical drug used to treat high blood pressure and reduce the risk of stroke in certain people with heart disease. Danshen, prepared from the dried root and rhizome of Salvia miltiorrhiza Bunge, has been widely used for prevention and treatment of various cardiovascular and cerebrovascular diseases. There are more than 35 formulations containing Danshen indexed in the 2010 Chinese Pharmacopoeia, which are often combined with LST to treat cardiovascular and cerebrovascular diseases in the clinic. The effects of the two major components of Danshen, salvianolic acid B (SA-B) and tanshinone IIA (Tan IIA), on the pharmacokinetics of losartan and its metabolite, EXP3174, in rats were investigated by liquid chromatography coupled with mass spectrometry (LC-MS). Male Sprague-Dawley rats were randomly assigned to 3 groups: LST, LST+SA-B and LST+Tan IIA, and the main pharmacokinetic parameters were estimated after oral administration of LST, LST+SA-B and LST+Tan IIA. It was found that there are significant differences in the pharmacokinetic parameters among the three groups: Cmax, t1/2, AUC, AUMC in the LST+SA-B group was smaller than those in group LST, while larger in group LST+Tan IIA. Further, the effects of SA-B and Tan IIA on the metabolism of losartan was also investigated using rat liver microsomes in vitro. The results indicated that SA-B can induce the metabolism of LST, while Tan IIA can inhibit the metabolism of LST in rat liver microsomes in vitro by regulating activities of CYP450 enzymes. In addition, the effect of SA-B and Tan IIA on CYP3A4 and CYP2C9 expression was studied in Chang liver cells by western-blotting and Real-time PCR. It was concluded that the two components of Danshen, SA-B and Tan IIA have different influences on the metabolism of LST: SA-B can obviously speed up the metabolism of LST by inducing CYP3A4/CYP2C9 activities and expression, however, Tan IIA can slow down the metabolism of LST by inhibiting CYP3A4/CYP2C9 activities.

Multiplex Phenotyping for Systems Medicine: A One-Point Optimized Practical Sampling Strategy for Simultaneous Estimation of CYP1A2, CYP2C9, CYP2C19, and CYP2D6 Activities Using a Cocktail Approach.

Phenotyping of the CYP450 enzyme activities contributes to personalized medicine, but the past phenotyping approaches have followed a piecemeal strategy measuring single enzyme activities in vivo. A barrier to phenotyping of populations in rural and remote areas is the limited time and resources for sample collection. The CEIBA cocktail approach allows metabolic capacity estimation of multiple CYP450 enzymes in a single sample analysis, but the attendant sample collection schemes for applications in diverse global settings are yet to be optimized. The present study aimed to select an optimal matrix to simultaneously analyze CYP450 enzyme activities so as to simplify the sampling schemes in the phenotyping protocol to enhance its throughput and feasibility in native populations or in remote and underserviced geographies and social contexts. We evaluated 13 Ecuadorian healthy volunteers for CYP1A2, CYP2C9, CYP2C19, and CYP2D6 genotypes and their metabolic phenotypes, including CYP3A4, in plasma and urine after administering one reduced dose of caffeine, losartan, omeprazole, and dextromethorphan. Pharmacokinetic analyses were performed, and the correlation between AUC parent/AUC metabolite and the ratio between concentrations of probe drugs and their corresponding metabolites at timepoints ranging from 0 to 12 hours post-dose were analyzed. A single sampling timepoint, 4 hours post-dose in plasma, was identified as optimal to reflect the metabolic activity of the attendant CYP450 enzymes. This study optimizes the CEIBA multiplexed phenotyping approach and offers new ways forward for integrated drug metabolism analyses, in the pursuit of global personalized medicine applications in resource-limited regions, be they in developed or developing countries.

Can the CEIBA Cocktail Designed for Human Cytochrome P450 Enzymes be Used in the Rat for Drug Interaction Studies?

Purpose - The CEIBA cocktail consisting of caffeine (CAF), omeprazole (OZ), dextromethorphan (DM) and losartan (LOS) was previously proposed for the clinical phenotyping of five major human cytochrome P450 (CYP) isoenzymes. This work aimed to assess the usefulness of CEIBA cocktail to study non-clinical drug interactions in the rat. Methods - Wistar rats were divided into five groups to receive a single-oral dose of each probe drug (CAF, OZ, LOS, DM), individually or in combination as a cocktail. Plasma concentrations of the probe drugs and their metabolites [paraxanthine (1,7-X), 5-hydroxyomeprazole (5-OZ), losartan carboxylic acid (E-3174), dextrorphan (DX) and 3-methoxymorphinan (3-MM)] were determined by LC-MS/MS, and the corresponding pharmacokinetic parameters were estimated by non-compartmental analysis. The AUC0-t and Cmax drug/metabolite ratios (phenotypic metrics) were calculated for each probe drug and compared (probe alone versus cocktail). Results - The primary analysis of the pharmacokinetic data suggested the occurrence of pharmacokinetic-based drug interactions when the probe drugs were concurrently administered; such interactions were documented for CAF, 1,7-X, DX and E-3174. Nevertheless, except for the LOS/E-3174 probe drug-metabolite pair (p<0.05), there was little evidence that the probe drugs interacted metabolically as the metabolic ratios calculated were similar in both approaches. Moreover, no evidence was found for relevant pharmacodynamic interactions. Conclusion - CEIBA cocktail seems to be a useful tool to investigate drug interactions involving CYP isoenzymes in the rat, particularly at the level of CYP1A2, CYP2D1/2 and CYP2D2 isoforms using the CAF/1,7-X, OZ/5-OZ and DM/DX metabolic ratios, respectively. 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.

Simultaneous Determination and Pharmacokinetics of Metolazone, Losartan and Losartan Carboxylic Acid in Rat Plasma by HPLC-ESI-MS-MS.

For the first time, we developed and validated a highly sensitive, selective and rapid HPLC-ESI-MS-MS method for simultaneous quantification of metolazone (MET), losartan (LOS) and its metabolite losartan carboxylic acid (LCA) in rat plasma. After solid-phase extraction, the analytes and internal standard (irbesartan) were extracted from 100 µL plasma sample on an Agilent Poroshell 120, EC-C18 (50 × 4.6 mm, i.d., 2.7 µm) column using 5 µL injection volume with a total run time of 3 min. Acidified methanol/water mixture was used as a mobile phase. The parent → product ion transitions for MET (m/z 366.0 → 258.9), LOS (m/z 423.2 → 207.0), LCA (m/z 437.0 → 235.1) and IS (m/z 429.2 → 207.0) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ion mode. The method was found to be linear in the range of 0.05-250 for MET, 2-3,000 for LOS and 4-3,500 ng/mL for LCA. The method was validated with respect to selectivity, linearity, accuracy, precision, recovery and stability according to accepted regulatory guidelines. The described method was successfully applied to preclinical pharmacokinetic studies of analytes after an oral administration of mixture of MET (1 mg/kg) and LOS (10 mg/kg) in rats.

A new spectrofluorimetric method for determination of losartan potassium in rabbit plasma and its application to pharmacokinetic study.

A new spectrofluorimetric method to determine losartan potassium (LP) in rabbit plasma is described. The method was based on measuring the native fluorescence of LP in acidic medium. Optimum excitation and emission wavelengths were found to be 248 nm and 410 nm, respectively, in methanol that was diluted with a sulfurous acid solution LP was extracted from rabbit plasma by methyl-tertiary-butyl-ether in acidic media and then back extracted with NaOH. The calibration curves were linear between 0.025 and 0.5 µg/mL with a lower limit of detection 0.004 µg/mL. Precision and accuracy values of the method were calculated as lower than 4.97% and ± 5.68, respectively and the recovery of LP from rabbit plasma was higher than 91.1%. In addition, stability studies of LP in rabbit plasma were carried out and demonstrated its good stability at - 20 °C and at room temperature. The developed and validated method was successfully applied for estimating the pharmacokinetic parameters of LP following oral administrations of a single 10 mg LP/kg to rabbits and it could be concluded that the method can be applied to clinical trials.

[EVALUATION OF THE PHARMACOKINETIC INTERACTION OF AFOBAZOLE WITH CYP2C9 ENZYME DRUG SUBSTRATE OF CYTOCHROME P450].

We have studied the pharmacokinetics of drug-marker of cytochrome P450 isoenzyme CYP2C9 (losartan) and its metabolite E-3174 after subchronic oral administration of afobazole in doses 5 and 25 mg/kg in rats. The metabolic ratio (MR) of E-3174/Losartan was calculated. The pharmacokinetic parameters of losartan and its metabolite on the background of 4-day afabazole administration 5 mg/kg dose were not significantly different from analogous values calculated for the control group of rats. Therefore, afobazole in the effective anxiolytic dose did not change the MR value of metabolized P450 isoform. A five-fold dose increase in the afobazole dose led to significant difference in pharmacokinetic parameters, including A UC0-t, Cmax, Kel, t1/2el, MRT, CL/F, and Vd/F of losartan and AUC0-T, Cmax, and Tmax of E-3174. These findings are indicative of the induction of CYP2C9 isoenzyme by afobazole.

Evaluation of felodipine as a potential perpetrator of pharmacokinetic drug-drug interactions.

OBJECTIVE: To evaluate felodipine as a potential perpetrator of pharmacokinetic drug-drug interactions (PK-DDIs) involving cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp). METHODS: Felodipine extended-release 10 mg was administered daily to six healthy subjects for 7 days (days 1-7). Subjects were administered a modified Inje cocktail comprising the selective probe substrates caffeine 100 mg (CYP1A2), losartan 25 mg (CYP2C9), omeprazole 20 mg (CYP2C19), dextromethorphan 30 mg (CYP2D6), midazolam 2 mg (CYP3A) and digoxin 250 µg (P-gp) on day 0 (prior to felodipine exposure) and day 7 (after felodipine exposure). Plasma samples were collected over 24 h and drug concentrations measured by UPLC-MS/MS. RESULTS: The geometric means of the area under the plasma concentration-time curve ratios (probe AUC after felodipine exposure/probe AUC prior to felodipine exposure) and 95% confidence intervals for each probe were: caffeine 0.91 (0.64-1.30), losartan 1.05 (0.95-1.15), omeprazole 1.17 (0.78-1.76), dextromethorphan 1.46 (1.00-2.12), midazolam 1.23 (0.99-1.52) and digoxin 1.01 (0.89-1.15). CONCLUSION: Felodipine may be a weak in vivo inhibitor of CYP3A and CYP2D6 but is unlikely to act as a significant perpetrator of PK-DDIs.

Drug-drug interactions between sucroferric oxyhydroxide and losartan, furosemide, omeprazole, digoxin and warfarin in healthy subjects.

BACKGROUND: The novel iron-based phosphate binder sucroferric oxyhydroxide is being investigated for the treatment of hyperphosphatemia. Patients with chronic kidney disease often have multiple comorbidities that may necessitate the daily use of several types of medication. Therefore, the potential pharmacokinetic drug-drug interactions between sucroferric oxyhydroxide and selected drugs commonly taken by dialysis patients were investigated. METHODS: Five Phase I, single-center, open-label, randomized, three-period crossover studies in healthy volunteers investigated the effect of a single dose of sucroferric oxyhydroxide 1 g (based on iron content) on the pharmacokinetics of losartan 100 mg, furosemide 40 mg, omeprazole 40 mg, digoxin 0.5 mg and warfarin 10 mg. Pharmacokinetic parameters [including area under the plasma concentration-time curve (AUC) from time 0 extrapolated to infinite time (AUC0-∞) and from 0 to 24 h (AUC0-24)] for these drugs were determined: alone in the presence of food; with sucroferric oxyhydroxide in the presence of food; 2 h after food and sucroferric oxyhydroxide administration. RESULTS: Systemic exposure based on AUC0-∞ for all drugs, and AUC0-24 for all drugs except omeprazole (for which AUC 0-8 h was measured), was unaffected to a clinically significant extent by the presence of sucroferric oxyhydroxide, irrespective of whether sucroferric oxyhydroxide was administered with the drug or 2 h earlier. CONCLUSIONS: There is a low risk of drug-drug interactions between sucroferric oxyhydroxide and losartan, furosemide, digoxin and warfarin. There is also a low risk of drug-drug interaction with omeprazole (based on AUC0-∞ values). Therefore, sucroferric oxyhydroxide may be administered concomitantly without the need to adjust the dosage regimens of these drugs.