Development and validation of an UPLC-MS/MS method for the simultaneous determination of fexofenadine and olmesartan in human serum: Application to in vivo pharmacokinetic studies.

A sensitive, reproducible, robust, high-throughput ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the simultaneous quantification of fexofenadine and olmesartan in human serum. Samples (50 µL) undergo protein precipitation prior to UPLC-MS/MS analysis. The analytes were separated using an Acquity BEH C18 column (2.1 mm × 50 mm, 1.7 µm) at a flow rate of 0.5 mL/min using a gradient elution with a total run time of 4 min. The analytes were detected in positive ion mode and selected reaction monitoring (SRM) was used for quantitation. The standard curve concentration range was 1.0-500.0 ng/mL for both analytes and each analyte showed excellent linearity with correlation coefficients (R2 > 0.99). The intra- and inter-day accuracy and precision were ±15% for each analyte, and excellent recovery was demonstrated (93-98%) for both analytes. The method is well suited for high-throughput quantitative determination of fexofenadine and olmesartan simultaneously and was successfully applied to an in vivo pharmacokinetic and transporter phenotyping study in humans.

Development of a simple method for measuring tedizolid concentration in human serum using HPLC with a fluorescent detector.

ABSTRACT: The objective of the present study was to develop a method to measure tedizolid (TZD) concentration for studying target concentration intervention, pharmacokinetics, and pharmacodynamics of TZD. We established a high-performance liquid chromatography-fluorescence detector assay to measure the TZD concentration in serum for clinical application. Chromatographic separation was carried out on a 5 µm octadecyl silane hypersil column 150 mm × 4.6 mm. The mobile phase consisted of 0.1 M phosphoric acid and methanol (60:40, pH 7.0). Detection was performed at 300 nm and 340 nm for the excitation and emission wavelengths, respectively. The average retention times of TZD and the internal standard were 12.9 and 8.8 min, respectively. High linearity was exhibited over a concentration range of 0.025 to 10.0 µg/mL for TZD (R2 > 0.999). The intra- and inter-assay accuracies of TZD were 99.2% to 107.0% and 99.2% to 107.7%, respectively. The lower limit of quantitation and the lower limit of detection for TZD measurement were 0.025 and 0.01 µg/mL, respectively. The extraction recoveries of TZD were 100.4% to 114.1%.The high-performance liquid chromatography method developed in this study could separate the analytes with a single eluent (isocratic system), within a total run time of 15 min. Both TZD and IS were well separated, without interference from the peaks. Sharp peaks were observed in the chromatograms; problems such as double peaks, shoulder peaks, and broadened peaks were not observed. The proposed method showed acceptable analytical performance and could be used to evaluate serum TZD concentrations in patients.

Simultaneous quantification of plasma levels of 12 antimicrobial agents including carbapenem, anti-methicillin-resistant Staphylococcus aureus agent, quinolone and azole used in intensive care unit using UHPLC-MS/MS method.

OBJECTIVES: Critically ill patients in intensive care unit (ICU) are susceptible to infectious diseases, thus empirical therapy is recommended. However, the therapeutic effect in ICU patients is difficult to predict due to fluctuation in pharmacokinetics because of various factors. This problem can be solved by developing personalized medicine through therapeutic drug monitoring. However, when different measurement systems are used for various drugs, measurements are complicated and time consuming in clinical practice. In this study, we aimed to develop an assay using ultra-high performance liquid chromatography coupled with tandem mass spectrometry for simultaneous quantification of 12 antimicrobial agents commonly used in ICU: doripenem, meropenem, linezolid, tedizolid, daptomycin, ciprofloxacin, levofloxacin, pazufloxacin, fluconazole, voriconazole, voriconazole N-oxide which is a major metabolite of voriconazole, and posaconazole. DESIGN & METHODS: Plasma protein was precipitated by adding acetonitrile and 50% MeOH containing standard and labeled IS. The analytes were separated with an ACQUITY UHPLC CSH C18 column, under a gradient mobile phase consisting of water and acetonitrile containing 0.1% formic acid and 2 mM ammonium formate. RESULTS: The method fulfilled the criteria of US Food and Drug Administration for assay validation. The recovery rate was more than 84.8%. Matrix effect ranged from 79.1% to 119.3%. All the calibration curves showed good linearity (back calculation of calibrators: relative error ≤ 15%) over wide concentration ranges, which allowed determination of Cmax and Ctrough. Clinical applicability of the novel method was confirmed. CONCLUSIONS: We have developed an assay for simultaneous quantification of 12 antimicrobial agents using a small sample volume of 50 µL with a short assay time of 7 min. Our novel method may contribute to simultaneous calculation of pharmacokinetic and pharmacodynamic parameters.

Simultaneous determination of sacubitrilat and fimasartan in rat plasma by a triple quad liquid chromatography-tandem mass spectrometry method utilizing electrospray ionization in positive mode.

An LC-tandem mass spectrometry method was developed and validated for the simultaneous quantitation of fimasartan and sacubitrilat using positive ion mode. The protein precipitation method was employed for the extraction of fimasartan, sacubitrilat and alprazolam (internal standard) from rat heparinized plasma. Baseline separation of the analytes was accomplished using an ACE-5, C18 (4.6 × 50 mm) column and gradient elution of mobile phase A (5 mm ammonium formate and 0.1% formic acid in purified water) and B (acetonitrile:methanol, 80:20; v/v). All peaks of interest were eluted within a 5-min runtime. The quantitation was achieved in the selected reaction monitoring mode. The developed method was validated as per US Food and Drug Administration guidelines and met the pre-defined acceptance criteria. The method showed linearity from 5 to 10,000 ng/mL. The accuracy/precision of intra- and inter-batch assays was 96.64%/2.05% to 109.17%/13.70% and 100.74%/3.76% to 106.39%/9.75% for fimasartan and 100.02%/1.49% to 113.80%/9.38% and 100.75%/2.31% to 108.40%/7.74% for sacubitrilat, respectively, in rat plasma. Fimasartan and sacubitrilat remained stable in rat plasma at different experimental conditions up to 21 days. The developed method was sensitive, selective and applied successfully to monitor plasma concentrations of fimasartan and sacubitrilat in an oral rat pharmacokinetic study.

Cenobamate for the treatment of focal epilepsies.

INTRODUCTION: Antiseizure drugs (ASDs) play a central and crucial role in the treatment of epilepsy patients because the majority require anticonvulsant treatment for an extended period of time. Due to the fact that 30% of patients are refractory to medical treatment, new therapeutic options are necessary. Cenobamate is the latest approved antiepileptic drug in focal epilepsy, and its mode of action is thought to be mediated by blocking voltage-gated sodium channels and interaction with the GABAergic system. AREAS COVERED: This article reviews animal studies, pharmacokinetics, pharmacodynamics, and the phase 1 to 3 trials and open-label extension data on cenobamate. EXPERT OPINION: Cenobamate has the potential to perform as an important ASD because trial data are indicative of remarkable responder and seizure freedom rates so far not seen with other ASDs. Cenobamate demonstrated significant efficacy at a dosage between 100 and 400 mg per day. The side-effect profile of this drug is comparable to other ASDs and is mainly CNS related; in particular, somnolence, dizziness, headache, diplopia, and nystagmus. However, slow titration is mandatory to decrease the risk of drug rash with eosinophilia and systemic symptoms (DRESS) that was observed in several patients with fast uptitration schemes.

Comparison of the Pharmacokinetics of Highly Variable Drugs in Healthy Subjects Using a Partial Replicated Crossover Study: A Fixed-Dose Combination of Fimasartan 120 mg and Atorvastatin 40 mg versus Separate Tablets.

PURPOSE: A fixed-dose combination (FDC) of fimasartan and atorvastatin is used to treat hypertension and dyslipidemia. The peak plasma concentration (Cmax) of fimasartan and atorvastatin has a large intra-subject variability with a maximum coefficient of variation of 65% and 48%, respectively. Therefore, both drugs are classified as highly variable drugs. The purpose of this study was to compare the pharmacokinetics (PK) between a FDC of fimasartan 120 mg and atorvastatin 40 mg versus separate tablets in healthy male Korean subjects. SUBJECTS AND METHODS: A randomized, single-dose, two-treatment, three-sequence, three-period, partial replicated crossover study was conducted with a 7-day washout interval between periods. Blood samples for fimasartan and atorvastatin were collected until 48 hours after administration in each period. PK parameters were calculated using the non-compartmental method. Geometric mean ratios (GMRs) for PK parameters of FDC to loose combination and their 90% confidence intervals (90% CIs) were estimated. RESULTS: A total of 56 subjects completed the study. GMRs (90% CIs) of the Cmax for fimasartan and atorvastatin were 1.08 (0.93-1.24) and 1.02 (0.92-1.13), respectively. The expanded 90% CIs of both drugs using the intra-subject variability was calculated range of 0.70-1.43 and 0.73-1.38, respectively. The corresponding values of area under the concentration-time curve from zero to the last measurable time point were 1.02 (0.97-1.08) and 1.02 (0.98-1.07), respectively. CONCLUSION: FDC of fimasartan 120 mg and atorvastatin 40 mg between their loose combination showed similar PK characteristics.

A Pharmacokinetic Drug Interaction Between Fimasartan and Linagliptin in Healthy Volunteers.

OBJECTIVE: Fimasartan, an angiotensin II type 1 receptor blocker, and linagliptin, a dipeptidyl-peptidase-4 inhibitor, are frequently coadministered to treat patients with hypertension and diabetes, respectively. This study sought to evaluate the pharmacokinetic interactions between fimasartan and linagliptin after co-administration in healthy Korean subjects. METHODS: The overall study was divided into two separate parts, with each part designed as an open-label, multiple-dose, two-period, and single-sequence study. In Part A, to investigate the effect of linagliptin on fimasartan, 25 subjects received 120 mg fimasartan alone once daily for seven days during Period I, and 120 mg fimasartan with 20 mg linagliptin for seven days during Period II. In Part B, to examine the effect of fimasartan on linagliptin, 12 subjects received only linagliptin once daily for seven days during Period I, followed by concomitant administration of fimasartan for seven days during Period II, at the same doses used in Part A. Serial blood samples were collected at scheduled intervals for up to 24 h after the last dose to determine the steady-state pharmacokinetics of both drugs. RESULTS: Thirty-six subjects completed the study. The geometric mean ratio and 90% confidence intervals for maximum plasma concentration at steady state (Cmax,ss) and area under the concentration-time curve at steady state (AUCτ,ss) of fimasartan with or without linagliptin were 1.2633 (0.9175-1.7396) and 1.1740 (1.0499-1.3126), respectively. The corresponding values for Cmax,ss and AUCτ,ss of linagliptin with or without fimasartan were 0.9804 (0.8480-1.1336) and 0.9950 (0.9322-1.0619), respectively. A total of eight adverse events (AEs) were reported and the incidence of AEs did not increase significantly with co-administration of the drugs. CONCLUSION: Our results suggest that there are no clinically significant pharmacokinetic interactions between fimasartan and linagliptin when co-administered. Treatments were well tolerated during the study, with no serious adverse effects. CLINICAL TRIAL REGISTRY: http://clinicaltrials.gov, NCT03250052.

Cenobamate (YKP3089) as adjunctive treatment for uncontrolled focal seizures in a large, phase 3, multicenter, open-label safety study.

OBJECTIVE: During the development of cenobamate, an antiseizure medication (ASM) for focal seizures, three cases of drug reaction with eosinophilia and systemic symptoms (DRESS) occurred. To mitigate the rate of DRESS, a start-low, go-slow approach was studied in an ongoing, open-label, multicenter study. Also examined were long-term safety of cenobamate and a method for managing the pharmacokinetic interaction between cenobamate, a 2C19 inhibitor, and concomitant phenytoin or phenobarbital. METHODS: Patients 18-70 years old with uncontrolled focal seizures taking stable doses of one to three ASMs were enrolled. Cenobamate 12.5 mg/d was initiated and increased at 2-week intervals to 25, 50, 100, 150, and 200 mg/d. Additional biweekly 50 mg/d increases to 400 mg/d were allowed. During titration, patients taking phenytoin or phenobarbital could not have their cenobamate titration rate or other concomitant ASMs adjusted; phenytoin/phenobarbital doses could be decreased by 25%-33%. RESULTS: At data cutoff (median treatment duration = 9 months), 1347 patients were enrolled, of whom 269 (20.0%) discontinued, most commonly due to adverse events (n = 137) and consent withdrawn for reason other than adverse event (n = 74); 1339 patients received ≥1 treatment dose (median modal dose = 200 mg). The most common treatment-emergent adverse events (TEAEs) were somnolence (28.1%), dizziness (23.6%), and fatigue (16.6%). Serious TEAEs occurred in 108 patients (8.1%), most commonly seizure (n = 14), epilepsy (n = 5), and pneumonia, fall, and dizziness (n = 4 each). No cases of DRESS were identified. In the phenytoin/phenobarbital groups, 43.4% (36/114) and 29.7% (11/51) of patients, respectively, had their doses decreased. At the end of titration, mean plasma phenytoin/phenobarbital levels were generally comparable to baseline. SIGNIFICANCE: No cases of DRESS were identified in 1339 patients exposed to cenobamate using a start-low (12.5 mg/d), go-slow titration approach. Cenobamate was generally well tolerated in the long term, with no new safety issues found. Phenytoin/phenobarbital dose reductions (25%-33%), when needed during cenobamate titration, maintained stable plasma levels.

Mass Balance, Metabolism, and Excretion of Cenobamate, a New Antiepileptic Drug, After a Single Oral Administration in Healthy Male Subjects.

BACKGROUND AND OBJECTIVE: Cenobamate is an antiepileptic drug for the treatment of partial-onset seizures. The current study was designed to assess the mass balance and the metabolic profiling of cenobamate in humans. METHODS: Absorption, metabolism, and excretion of cenobamate were investigated in healthy male subjects after a single oral dose of 400 mg of cenobamate containing 50 µCi of [14C]-cenobamate as capsule formulation. RESULTS: Cenobamate was rapidly (median time to maximum plasma concentration of 1.25 h) and extensively (≥ 88% of dose) absorbed. The mean cenobamate plasma concentration-time profile revealed a multiphasic elimination profile whereas the mean plasma/blood concentration-time curve for total radioactivity did not appear to be multiphasic, suggesting that elimination mechanisms for cenobamate and its metabolites may be different. Blood/plasma ratios observed for the area under the concentration-time curve (AUC) and peak concentration (both ~ 0.60) suggest a limited penetration of cenobamate and metabolites into red blood cells (RBCs). Eight cenobamate metabolites were identified across plasma, urine, and feces. Cenobamate was the main plasma radioactive component and M1 was the only metabolite detected in plasma (> 98% and < 2% total radioactivity AUC, respectively). All detected metabolites were found in urine, with M1 as the major radioactive component (mean cumulative recovery 37.7% of dose); unchanged cenobamate accounted for 6%. Metabolites comprised ~ 88% of the dose recovered in urine, indicating extensive metabolism by the kidneys and/or metabolites formed in the liver were rapidly eliminated from the bloodstream. However, cenobamate metabolites appear to be formed slowly. Minor amounts of cenobamate (0.48%) and five metabolites (≤ 1.75% each; M1, M3, M6, M7, M11) were recovered in feces. CONCLUSION: This study indicates that cenobamate is primarily eliminated in urine as metabolites. Cenobamate is the major circulating component in plasma after oral administration and has a limited penetration into RBCs.

Determination of free clindamycin, flucloxacillin or tedizolid in plasma: Pay attention to physiological conditions when using ultrafiltration.

Pharmacokinetic/pharmacodynamic indices of anti-infective drugs should be referenced to free drug concentrations. In the present study, clindamycin, flucloxacillin and tedizolid have been determined in human plasma by HPLC-UV. The drugs were separated isocratically within 3-6 min on a C18 column using mixtures of phosphate buffer-acetonitrile of pH 7.1-7.2. Sample treatment for the determination of total drug concentrations in plasma included extraction/back-extraction (clindamycin) or protein precipitation (flucloxacillin, tedizolid). The free drug concentrations were determined after ultrafiltration. An ultrafiltration device with a membrane consisting of regenerated cellulose proved to be suitable for all drugs. Maintaining a physiological pH was crucial for clindamycin, whereas maintaining body temperature was essential for tedizolid. The methods were applied to the analysis of total and free drug concentrations in clinical samples and were sufficiently sensitive for pharmacokinetic studies and therapeutic drug monitoring.

Quantitative bio-analysis of pitavastatin and candesartan in rat plasma by HPLC-UV: Assessment of pharmacokinetic drug-drug interaction.

A novel, precise, accurate and rapid HPLC-UV method was developed, optimised and fully validated for simultaneous estimation of pitavastatin (PIT) and candesartan (CAN) in rat plasma using telmisartan as an internal standard. Following liquid-liquid extraction of the analytes from plasma, chromatographic separation was accomplished on a Waters Reliant C18 column (4.6 × 250 mm, 5 µm) using ACN-5 mM Sodium acetate buffer (80:20, v/v; pH adjusted to 3.5 with acetic acid) as mobile phase at a flow rate of 0.8 mL/min and wavelength of 234 nm. The calibration curves were linear over the concentration ranges of 2-400 ng/mL and 3-400 ng/mL for pitavastatin and candesartan respectively. The method when validated as per US-FDA guidelines was found to be precise as well as accurate. Extraction recovery observed for both analytes was above 90% as well as reproducible and consistent. Stability studies showed the samples to be stable over a long period covering from sample collection to final analysis. The method was successfully applied to investigate pharmacokinetic interaction between PIT and CAN in wistar rats. The mean plasma concentration-time curves of PIT and CAN showed that single PIT as well as CAN show similar pharmacokinetic properties to those obtained when co-administrated with each other (P value >0.05). Hence, there is no evidence for a potential drug-drug interaction between PIT and CAN. This information provides evidence for clinical rational use of CAN and PIT in cardiovascular patients.

Transfer of Candesartan Into Human Breast Milk.

BACKGROUND: There are currently no data regarding the transfer of candesartan into human milk. This report provides data on this transfer, an estimation of the amount breastfed infants receive, and plasma concentrations from two breastfed infants. CASES: Three breastfeeding mothers, all stabilized on candesartan (8-32 mg/d), provided milk and plasma samples over one dosing interval (24 hours). Two infant plasma samples were obtained. The amount the infants ingested was estimated to be 0.09% (95% CI 0.07-0.11) of the maternal dose (weight-adjusted). Candesartan was undetectable (less than 0.2 micrograms/L) in infant plasma samples. CONCLUSION: A relative infant dose of 0.09% suggests that maternal benefit from candesartan at standard therapeutic doses may outweigh risk in breastfeeding healthy, term infants.

Comparative pharmacokinetics of tedizolid in rat plasma and cerebrospinal fluid.

To investigate the possibility of tedizolid phosphate's application in the treatment of intracranial infection, a preclinical comparative pharmacokinetic study was designed. Based on the assumption that the classic efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) may participate in the transportation of TDZ, two groups of rats were intravenously administered 6 mg/kg tedizolid phosphate alone or 6 mg/kg tedizolid phosphate combined with 1 mg/kg elacridar which was an inhibitor of P-gp and BCRP. Plasma and cerebrospinal fluid samples were collected according to a pharmacokinetic schedule. All the plasma and cerebrospinal fluid samples were assessed with a validated LC-MS/MS method. The penetration ratio of tedizolid from the blood to cerebrospinal fluid was calculated, and a comparison of the penetration ratios between the two groups was made. The mean Cmax of tedizolid in the CSF in the tedizolid phosphate group and the tedizolid phosphate combined with elacridar group was 154 ng/mL and 300 ng/mL, respectively, and the mean penetration ratio of tedizolid in the tedizolid phosphate group and the tedizolid phosphate combined with elacridar group was 2.16% and 3.53%, respectively. The relatively high Cmax in the CSF proved the possibility of tedizolid phosphate's application in the treatment of intracranial infection, and the higher penetration ratios, Cmax, csf and AUCcsf of the rats in co-administered elacridar group than those in the single-administration group indicated that the transporters P-gp and BCRP might be involved in the transportation of tedizolid.

Evaluation of gender difference in pharmacokinetics of Candesartan cilexetil in the fasted state by RP-HPLC: A single dose comparative study.

To compare the pharmacokinetics of candesartan cilexetil in healthy male and female volunteers in order to identify possible influence of gender and to improve therapeutic outcomes, an HPLC method for the quantification of candesartan cilexetil was developed and validated. Total of 16 volunteers (8 male and 8 female) were registered. Candesartan cilexetil 16 mg was administered orally to all the volunteers and blood samples were collected at different time intervals between 0-72 hours. Plasma was separated and analysed by HPLC method. Pharmacokinetic parameters were calculated by using APO software MW/PHARM version 3.02 and compared in male and female volunteers. The developed HPLC method fulfils the criteria for linearity, accuracy and precision described in EMA guideline. The values for absorption rate constant (Ka), maximum plasma concentration (Cmax), volume of distribution (Vd) and Clearance (CL) were similar in male and female volunteers. No influence of gender was observed on overall pharmacokinetics of candesartan cilexetil. Therefore, no need for dose optimization while administering candesartan cilexetil in male and female patients was found based on the results of this study.

Effect of Food on the Pharmacokinetics of 2 Formulations of DRL-17822, a Novel Selective Cholesteryl Ester Transfer Protein (CETP) Inhibitor, in Healthy Males.

DRL-17822 is a novel selective cholesteryl ester transfer protein inhibitor that showed an increased exposure, including an increase of >20-fold of maximum concentration and area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration, following a high-fat breakfast using a nanocrystal formulation. To reduce this effect of food, we generated an amorphous solid dispersion formulation. In this study, we compared the food effect of both formulations of DRL-17822 in a 2-part randomized, open-label, 4-way crossover study involving healthy adult males 18-45 years of age. In both parts of the study, 12 subjects received both formulations of DRL-17822 in both the fasted and fed states; a low-fat breakfast was provided in the first part and a high-fat breakfast in the second part. Compared to the nanocrystal formulation, the amorphous solid dispersion formulation substantially increased DRL-17822 exposure in the fasted state, including increased maximum concentration, area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration, and area under plasma concentration-time curve from time zero to infinity. Following a high-fat breakfast, DRL-17822 exposure was increased to a lesser extent in the amorphous solid dispersion formulation compared to the nanocrystal formulation (P < .001). Moreover, compared to the nanocrystal formulation the amorphous solid dispersion formulation caused a more pronounced increase in high-density lipoprotein in the fasted state. Consuming breakfast increased the effect of DRL-17822 on high-density lipoprotein. Taken together, our results indicate that by improving its formulation, DRL-17822 has a favorable exposure profile and therefore a more predictable food effect profile.

Pharmacokinetic comparison of a fixed-dose combination versus concomitant administration of amlodipine, olmesartan, and rosuvastatin in healthy adult subjects.

Objective: The aim of this study was to compare the pharmacokinetic (PK) and safety profiles of a fixed dose combination (FDC) formulation and co-administration of amlodipine, olmesartan, and rosuvastatin. Materials and methods: This study was an open-label, randomized, cross-over design conducted in healthy male volunteers. All subjects received either a single FDC tablet containing amlodipine 10 mg/olmesartan 40 mg/rosuvastatin 20 mg, or were co-administered an FDC tablet containing amlodipine 10 mg/olmesartan 40 mg and a tablet containing rosuvastatin 20 mg, for each period, with 14-day washout periods. Plasma concentrations of amlodipine, olmesartan, and rosuvastatin were measured by liquid chromatography tandem mass spectrometry. Safety was evaluated by measuring vital signs, clinical laboratory parameters, physical examinations, and medical interviews. Results: Sixty-four subjects were enrolled, and 54 completed the study. The geometric mean ratios and 90% CI for the maximum plasma concentration (Cmax) and area under the curve from time zero to the last sampling time (AUCt) were 1.0716 (1.0369,1.1074) and 1.0497 (1.0243,1.0757) for amlodipine, 1.0396 (0.9818,1.1009) and 1.0138 (0.9716,1.0578) for olmesartan, and 1.0257 (0.9433,1.1152) and 1.0043 (0.9453,1.0669) for rosuvastatin. Fourteen cases of adverse events occurred in 12 subjects. There was no statistically significant clinical difference between the formulation groups. Conclusion: The 90% CI of the primary PK parameters were within the acceptance bioequivalence criteria, which is ln (0.8) and ln (1.25). These results indicate that the FDC formulation and co-administration of amlodipine, olmesartan and rosuvastatin are pharmacokinetically bioequivalent and have similar safety profiles.

A simple, rapid and fully validated HPLC method for simultaneous quantitative bio-analysis of rosuvastatin and candesartan in rat plasma: Application to pharmacokinetic interaction study.

A simple, precise and accurate HPLC method was developed, optimized and validated for simultaneous determination of rosuvastatin and candesartan in rat plasma using atorvastatin as an internal standard. Solid-phase extraction was used for sample cleanup and its subsequent optimization was carried out to achieve higher extraction efficiency and to eliminate matrix effect. A quality by design approach was used, wherein three-level factorial design was applied for optimization of mobile phase composition and for assessing the effect of pH of the mobile phase using Design Expert Software. Adequate separation for both analytes was achieved with a Waters C18 column (250 × 4.6 mm, 5 µm) using acetonitrile-5 mm sodium acetate buffer (70:30, v/v; pH adjusted to 3.5 with acetic acid) as a mobile phase at a flow rate of 1.0 mL/min and wavelength of 254 nm. The calibration curves were linear over the concentration ranges 5-150 and 10-300 ng/mL for rosuvastatin (ROS) and candesartan (CAN), respectively. The validated method was successfully applied to a pharmacokinetic study in Wistar rats and the data did not reveal any evidence for a potential drug-drug interaction between ROS and CAN. This information provides evidence for clinical rational use of ROS and CAN.

Neonatal exposure to a glyphosate-based herbicide alters the histofunctional differentiation of the ovaries and uterus in lambs.

The aim of the present study was to compare the effect of oral and subcutaneous exposure to a glyphosate-based herbicide (GBH) on the female reproductive system, specifically in the ovaries and uterus of prepubertal lambs. To this end, ewe lambs were exposed to a s.c. (n: 5) or an oral (n: 5) environmentally relevant dose of GBH (2 mg/kg/day) or to vehicle (controls, n: 12), from postnatal day (PND) 1 to PND14. Serum glyphosate and aminomethylphosphonic acid (AMPA) concentrations were measured on PND15 and PND45. The ovaries and uterus were obtained and weighed on PND45. Ovarian follicular dynamics and uterine morphological features were determined by picrosirius-hematoxylin staining. The proliferation marker Ki67 was evaluated by immunohistochemistry in ovarian and uterine samples. Glyphosate but not AMPA was detected in serum of exposed lambs on PND15, whereas neither glyphosate nor AMPA were detected on PND45. Controls were negative for glyphosate and AMPA on PND15 and PND45. GBH exposure did not affect ovarian or uterine weight. However, on PND45, the ovary of GBH-exposed lambs showed altered follicular dynamics, increased proliferation of granulosa and theca cells, and decreased mRNA expression of FSHR and GDF9, whereas their uterus showed decreased cell proliferation but no alterations in the histomorphology or gene expression. In conclusion, GBH exposure altered the ovarian follicular dynamics and gene expression, and the proliferative activity of the ovaries and uterus of lambs. It is noteworthy that all the adverse effects found in the ovaries and uterus of both GBH-exposed groups were similar, independently of the administration route.

Pharmacokinetic and bioequivalence study comparing a fimasartan/rosuvastatin fixed-dose combination with the concomitant administration of fimasartan and rosuvastatin in healthy subjects.

PURPOSE: A new fixed-dose combination (FDC) formulation of 120 mg fimasartan and 20 mg rosuvastatin was developed to increase therapeutic convenience and improve treatment compliance. METHODS: A randomized, open-label, single-dose, two-treatment, two-way crossover study with a 7-day washout period was conducted to compare the pharmacokinetic (PK) characteristics and bioequivalence between an FDC of fimasartan/rosuvastatin and the separate co-administration of fimasartan and rosuvastatin in healthy Korean volunteers. The plasma concentrations of fimasartan and rosuvastatin were analyzed by a validated liquid chromatography-tandem mass spectrometry method, for which serial blood samples were collected for up to 48 hours post-administration of fimasartan and 72 hours post-administration of rosuvastatin, in each period. The PK parameters were calculated using a non-compartmental method. RESULTS: A total of 78 subjects completed the study. All the 90% CIs of the geometric mean ratios (GMRs) fell within the predetermined acceptance range. The GMR and 90% CI for the area under the plasma concentration-time curve from time 0 to the last measurement (AUC0-t) and the maximum plasma concentration (Cmax) for fimasartan were 0.9999 (0.9391-1.0646) and 1.0399 (0.8665-1.2479), respectively. The GMR and 90% CI for the AUC0-t and Cmax for rosuvastatin were 1.0075 (0.9468-1.0722) and 1.0856 (0.9944-1.1852), respectively. Treatment with fimasartan and rosuvastatin was generally well tolerated without serious adverse events. CONCLUSION: The new FDC formulation of 120 mg fimasartan and 20 mg rosuvastatin can be substituted for the separate co-administration of fimasartan and rosuvastatin, for the advantage of better compliance with convenient therapeutic administration.

Development and validation of HPLC method for the determination of Candesartan in human plasma.

Candesartan (CAN), an ARB-blocker, antihypertensive, was analyzed in human plasma by a simple, accurate and precise RP-HPLC (reverse phase-High performance liquid chromatography assay method which was then validated for its accuracy, specificity and precision. The mobile phase has a constitution of acetone, diethylamine and distilled water, while Phosphoric acid was used to adjust the pH to 2.5±0.1. This mobile phase was run at 1.1ml/min and the fluorescence wavelength was set to 392 nm. A C-18 HPLC, column particle size (5 µm) Mediterranean Sea ® L x 1.D. 25cm x 4.6 mm (Supelcosil) , with auto sampler injection volume of 30µl ,an internal standard Valsartan was utilized for chromatographic detection. Candesartan took a retention time of 6±0.5 minutes. This method was validated by the parameters of selectivity, accuracy, precision, repeatability, reproducibility, recovery, linearity and stability. Candesartan's calibration curves were found to be linear in the range of 200ng/ml to 3.125ng/ml and the coefficient of determination (r2) was found to be 0.99. Analytical recovery obtained was above 88%. Hence, this method has been found to be useful for determining Candesartan in plasma.