Toxicokinetic and bioavailability studies on retrorsine in mice, and ketoconazole-induced alteration in toxicokinetic properties.

Retrorsine (RTS) is a toxic retronecine-type pyrrolizidine alkaloid, which is widely distributed. The purpose of this study was to develop a high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for serum RTS determination in mice. Serum samples were deproteinated by acetonitrile, separated on a C18 -PFP column and delivered at 0.8 ml/min with an eluting system composed of water containing 0.1% (v/v) formic acid and acetonitrile containing 0.1% (v/v) formic acid as mobile phases. RTS and the internal standard S-hexylglutathione (H-GSH) were quantitatively monitored with precursor-to-product transitions of m/z 352.1 → 120.1 and m/z 392.2 → 246.3, respectively. The method showed excellent linearity over the concentration range 0.05-50 µg/ml, with correlation coefficient r2 = 0.9992. The extraction recovery was >86.34%, and the matrix effect was not significant. Inter- and intra-day precisions (RSD) were <4.99%. The validated LC-MS/MS method was successfully applied to study the toxicokinetic profiles of serum RTS in mice after intravenous, oral administration and co-treated with ketoconazole, which showed that RTS displayed a long half-life (~11.05 h) and good bioavailability (81.80%). Co-administration of ketoconazole (KTZ) increased the peak serum concentration and area under the concentration-time curve and decreased the clearance and mean residence time. Summing up, a new standardized method was established for quantitative determination of RTS in sera.

Novel Application of Pentabromobenzyl Column for Simultaneous Determination of Eight Antifungal Drugs Using High-performance Liquid Chromatography.

AIM: A new, accurate and sensitive reversed-phase high-performance liquid chromatography (RP-HPLC) as an analytical method for the quantitative determination of eight antifungal drugs in spiked human plasma has been described optimized and validated. MATERIALS AND METHODS: The analyzed compounds were voriconazole (VOR), luliconazole (LUL), clotrimazole (CLO), tioconazole (TIO), posaconazole (POS), ketoconazole (KET), sertaconazole (SER) and terconazole (TER). RESULTS: The separation of the analyzed compounds was conducted using a novel pentabromobenzyl column known as COSMOSIL PBB-R (150 mm × 4.6 mm I.D., particle size 5 µm). The analysis of the studied drugs was determined within 14 min using a diode array detector and the mobile phase consisted of: 10 mM potassium dihydrogen phosphate buffer (pH 2.1): Methanol (2: 98 v/v). A linear response was observed for all compounds in the range of concentration studied. Sample preparation was done through liquid-liquid extraction using diethyl ether. CONCLUSION: This proposed method was validated in terms of linearity, limit of quantification, limit of detection, accuracy, precision and selectivity. The method was successfully applied for the determination of these drugs in their pharmaceutical formulations and in human plasma samples.

Changes in Bile Acid Concentrations after Administration of Ketoconazole or Rifampicin to Chimeric Mice with Humanized Liver.

Drug-induced liver injury (DILI) is a common side effect of several medications and is considered a major factor responsible for the discontinuation of drugs during their development. Cholestasis is a DILI that results from impairment of bile acid transporters, such as the bile salt export pump (BSEP), leading to accumulation of bile acids. Both in vitro and in vivo studies are required to predict the risk of drug-induced cholestasis. In the present study, we used chimeric mice with humanized liver as a model to study drug-induced cholestasis. Administration of a single dose of ketoconazole or rifampicin, known to potentially cause cholestasis by inhibiting BSEP, did not result in elevated levels of alkaline phosphatase (ALP), which are known hepatic biomarkers. The concentration of taurodeoxycholic acid increased in the liver after ketoconazole administration, whereas rifampicin resulted in increased tauromuricholic acid and taurocholic acid (TCA) levels in the liver and plasma. Furthermore, rifampicin resulted in an increase in the uniform distribution of a compound with m/z 514.3, presumed as TCA through imaging mass spectrometry. The mRNA levels of bile acid-related genes were also altered after treatment with ketoconazole or rifampicin. We believe these observations to be a part of a feedback mechanism to decrease bile acid concentrations. The changes in bile acid concentrations results may reflect the initial responses of the human body to cholestasis. Furthermore, these findings may contribute to the screening of drug candidates, thereby avoiding drug-induced cholestasis during clinical trials and drug development.

Improved Prediction of in Vivo Supersaturation and Precipitation of Poorly Soluble Weakly Basic Drugs Using a Biorelevant Bicarbonate Buffer in a Gastrointestinal Transfer Model.

The characterization of intestinal dissolution of poorly soluble drugs represents a key task during the development of both new drug candidates and drug products. The bicarbonate buffer is considered as the most biorelevant buffer for simulating intestinal conditions. However, because of its complex nature, being the volatility of CO2, it has only been rarely used in the past. The aim of this study was to investigate the effect of a biorelevant bicarbonate buffer on intestinal supersaturation and precipitation of poorly soluble drugs using a gastrointestinal (GI) transfer model. Therefore, the results of ketoconazole, pazopanib, and lapatinib transfer model experiments using FaSSIFbicarbonate were compared with the results obtained using standard FaSSIFphosphate. Additionally, the effect of hydroxypropyl methylcellulose acetate succinate (HPMCAS) as a precipitation inhibitor was investigated in both buffer systems and compared to rat pharmacokinetic (PK) studies with and without coadministration of HPMCAS as a precipitation inhibitor. While HPMCAS was found to be an effective precipitation inhibitor for all drugs in FaSSIFphosphate, the effect in FaSSIFbicarbonate was much less pronounced. The PK studies revealed that HPMCAS did not increase the exposure of any of the model compounds significantly, indicating that the transfer model employing bicarbonate-buffered FaSSIF has a better predictive power compared to the model using phosphate-buffered FaSSIF. Hence, the application of a bicarbonate buffer in a transfer model set-up represents a promising approach to increase the predictive power of this in vitrotool and to contribute to the development of drug substances and drug products in a more biorelevant way.

A novel high-performance liquid chromatographic method combined with fluorescence detection for determination of ertugliflozin in rat plasma: Assessment of pharmacokinetic drug interaction potential of ertugliflozin with mefenamic acid and ketoconazole.

Ertugliflozin (ERTU) is a novel, potent, and highly selective sodium glucose cotransporter 2 inhibitor that has been recently approved for the treatment of type 2 diabetes mellitus. We describe a novel bioanalytical method using high-performance liquid chromatography (HPLC) coupled with fluorescence detection for quantitative determination of ERTU in rat plasma. Acetonitrile-based protein precipitation method was used for sample preparation, and chromatographic separation was performed on a Kinetex® C18 column with an isocratic mobile phase comprising acetonitrile and 10 mM potassium phosphate buffer (pH 6.0). The eluent was monitored by a fluorescence detector at an optimized excitation/emission wavelength pair of 277/320 nm. The method was validated to demonstrate the selectivity, linearity (ranging from 4 to 2000 ng/mL), precision, accuracy, recovery, matrix effect, and stability in line with the current FDA guidelines. The newly developed method was successfully applied to investigate the pharmacokinetic interactions of ERTU with mefenamic acid (MEF) and ketoconazole (KET). The findings of the present study revealed that the pharmacokinetics of ERTU may be altered by concurrent administration of MEF and KET in rats. To our knowledge, the present study is the first to develop a validated bioanalytical method for quantification of ERTU using HPLC coupled with fluorescence detection and to assess the drug interaction potential of ERTU with non-steroidal anti-inflammatory (MEF) and azole antifungal (KET) drugs.

Prediction of Ketoconazole absorption using an updated in vitro transfer model coupled to physiologically based pharmacokinetic modelling.

The aim of this study was to optimize the in vitro transfer model and to increase its biorelevance to more accurately mimic the in vivo supersaturation and precipitation behaviour of weak basic drugs. Therefore, disintegration of the formulation, volumes of the stomach and intestinal compartments, transfer rate, bile salt concentration, pH range and paddle speed were varied over a physiological relevant range. The supersaturation and precipitation data from these experiments for Ketoconazole (KTZ) were coupled to physiologically based pharmacokinetic (PBPK) model using Stella® software, which also incorporated the disposition kinetics of KTZ taken from the literature, in order to simulate the oral absorption and plasma profile in humans. As expected for a poorly soluble weak base, KTZ demonstrated supersaturation followed by precipitation under various in vitro conditions simulating the proximal small intestine with the results influenced by transfer rate, hydrodynamics, volume, bile salt concentration and pH values. When the in vitro data representing the "average" GI conditions was coupled to the PBPK model, the simulated profiles came closest to the observed mean plasma profiles for KTZ. In line with the high permeability of KTZ, the simulated profiles were highly influenced by supersaturation whilst precipitation was not predicted to occur in vivo. A physiological relevant in vitro "standard" transfer model setup to investigate supersaturation and precipitation was established. For translating the in vitro data to the in vivo setting, it is important that permeability is considered which can be achieved by coupling the in vitro data to PBPK modelling.

A rapid MCM-41 dispersive micro-solid phase extraction coupled with LC/MS/MS for quantification of ketoconazole and voriconazole in biological fluids.

A rapid dispersive micro-solid phase extraction (D-µ-SPE) combined with LC/MS/MS method was developed and validated for the determination of ketoconazole and voriconazole in human urine and plasma samples. Synthesized mesoporous silica MCM-41 was used as sorbent in d-µ-SPE of the azole compounds from biological fluids. Important D-µ-SPE parameters, namely type desorption solvent, extraction time, sample pH, salt addition, desorption time, amount of sorbent and sample volume were optimized. Liquid chromatographic separations were carried out on a Zorbax SB-C18 column (2.1 × 100 mm, 3.5 µm), using a mobile phase of acetonitrile-0.05% formic acid in 5 mm ammonium acetate buffer (70:30, v/v). A triple quadrupole mass spectrometer with positive ionization mode was used for the determination of target analytes. Under the optimized conditions, the calibration curves showed good linearity in the range of 0.1-10,000 µg/L with satisfactory limit of detection (≤0.06 µg/L) and limit of quantitation (≤0.3 µg/L). The proposed method also showed acceptable intra- and inter-day precisions for ketoconazole and voriconazole from urine and human plasma with RSD ≤16.5% and good relative recoveries in the range 84.3-114.8%. The MCM-41-D-µ-SPE method proved to be rapid and simple and requires a small volume of organic solvent (200 µL); thus it is advantageous for routine drug analysis.

The absorption kinetics of ketoconazole plays a major role in explaining the reported variability in the level of interaction with midazolam: Interplay between formulation and inhibition of gut wall and liver metabolism.

The impact of different single oral doses of ketoconazole (KTZ) (100, 200 and 400 mg) and of staggering its dosage (400 mg at -12, -2, 0, 2 and 4 h), with respect to the administration of a single 5 mg oral dose of midazolam (MDZ) on the extent of inhibition of the metabolism of the latter, was evaluated in healthy subjects in two separate studies. Escalation of the ketoconazole dosage resulted in 2.3 (1.9), 2.7 (1.7) and 4.2 (2.5) -fold increases in the mean AUC(0,12h) (and Cmax ) values of midazolam. Dose-staggering was associated with 3.9 (2.5), 4.9 (2.9), 5.4 (2.8), 2.0 (1.3) and 1.2 (0.9) -fold increases in the mean AUC(0,12h) (and Cmax ) of midazolam. These findings could be predicted by physiologically based pharmacokinetic (PBPK) modelling using the ADAM (advanced dissolution absorption and metabolism) model within the Simcyp Simulator (Version 12 Release 2) to characterize the absorption kinetics of ketoconazole with respect to disintegration time, supersaturation ratio and precipitation rate. This study also emphasizes a need to account for inter-individual variability in the gut wall and systemic exposure of inhibitors with physicochemical properties similar to ketoconazole, in particular in their rate of oral absorption and when using different pharmaceutical formulations, in designing and evaluating the extent of drug-drug interactions. Copyright © 2016 John Wiley & Sons, Ltd.

Edoxaban drug-drug interactions with ketoconazole, erythromycin, and cyclosporine.

AIMS: Edoxaban, a novel factor Xa inhibitor, is a substrate of cytochrome P450 3 A4 (CYP3A4) and the efflux transporter P-glycoprotein (P-gp). Three edoxaban drug-drug interaction studies examined the effects of P-gp inhibitors with varying degrees of CYP3A4 inhibition. METHODS: In each study, healthy subjects received a single oral dose of 60 mg edoxaban with or without an oral dual P-gp/CYP3A4 inhibitor as follows: ketoconazole 400 mg once daily for 7 days, edoxaban on day 4; erythromycin 500 mg four times daily for 8 days, edoxaban on day 7; or single dose of cyclosporine 500 mg with edoxaban. Serial plasma samples were obtained for pharmacokinetics and pharmacodynamics. Safety was assessed throughout the study. RESULTS: Coadministration of ketoconazole, erythromycin, or cyclosporine increased edoxaban total exposure by 87%, 85%, and 73%, respectively, and the peak concentration by 89%, 68%, and 74%, respectively, compared with edoxaban alone. The half-life did not change appreciably. Exposure of M4, the major active edoxaban metabolite, was consistent when edoxaban was administered alone or with ketoconazole and erythromycin. With cyclosporine, M4 total exposure increased by 6.9-fold and peak exposure by 8.7-fold, suggesting an additional interaction. Pharmacodynamic effects were reflective of increased edoxaban exposure. No clinically significant adverse events were observed. CONCLUSIONS: Administration of dual inhibitors of P-gp and CYP3A4 increased edoxaban exposure by less than two-fold. This effect appears to be primarily due to inhibition of P-gp. The impact of CYP3A4 inhibition appears to be less pronounced, and its contribution to total clearance appears limited in healthy subjects.

A highly sensitive LC-MS/MS method for determination of ketoconazole in human plasma: Application to a clinical study of the exposure to ketoconazole in patients after topical administration.

A simple, rapid and highly sensitive LC-MS/MS method was developed and validated for the determination of ketoconazole in human plasma. Sample preparation was accomplished through a single step liquid-liquid extraction by ethyl acetate. The chromatography separation was carried out on a Hedera CN (150mm×2.1mm, 5µm) column with isocratic elution using acetonitrile and 10mM ammonium acetate containing 0.1% formic acid (45:55, v/v) as the mobile phase. The flow rate was 0.5mL/min. Detection was performed in the positive ion electrospray ionization mode using multiple reaction monitoring of the transitions of 531.2→489.3 and 286.1→217.1 for ketoconazole and letrozole (the internal standard), respectively. The method exhibited good linearity over the concentration range of 0.01-12ng/mL for ketoconazole. The intra- and inter-batch precision and accuracy of ketoconazole were all within the acceptable criteria. The method was successfully applied to a clinical study of the exposure to ketoconazole in Chinese seborrheic dermatitis patients after topical administration of two ketoconazole formulations of foam and lotion, respectively. The study results showed that there was little systemic absorption of ketoconazole in patients for the two formulations, and the ketoconazole foam and lotion are safe therapeutic drugs for seborrheic dermatitis patients.

Urinary 6ß-Hydroxycortisol/Cortisol Ratio Most Highly Correlates With Midazolam Clearance Under Hepatic CYP3A Inhibition and Induction in Females: A Pharmacometabolomics Approach.

Endogenous metabolites of cytochrome P450 (CYP3A) are useful in predicting drug-drug interactions between in vivo CYP3A inhibitors and inducers for clinical applications of CYP3A substrate drugs. This study aimed to develop predictable markers of the magnitude of hepatic CYP3A induction and inhibition in healthy female subjects using pharmacometabolomics. Twelve female subjects received midazolam during three study phases: 1 mg midazolam (control phase), 1 mg midazolam after pretreatment with 400 mg ketoconazole once daily for 4 days (CYP3A inhibition phase), and 2.5 mg midazolam after pretreatment with 600 mg rifampicin once daily for 10 days (CYP3A induction phase). Throughout the study, blood samples were collected 24 h after midazolam administration and urine samples at 12-h intervals during the 24 h before and after midazolam administration for the analysis of endogenous steroid metabolites. A statistical model was generated to predict midazolam clearance using measurements of endogenous metabolites associated with the inhibition and induction of CYP3A. Mean midazolam clearance decreased to ∼20% of control levels during the inhibition phase and increased more than 2-fold during the induction phase. Of the urine and plasma metabolites measured, the 6ß-hydroxycortisol/cortisol ratio was most significantly correlated with midazolam clearance during hepatic CYP3A inhibition and induction. Our results suggest that the urinary 6ß-hydroxycortisol/cortisol ratio is the best predictor of hepatic CYP3A activity under both maximal inhibition and maximal induction. Furthermore, the predictive model including 6ß-hydroxycortisol/cortisol as a covariate could be applied to predict the magnitude of CYP3A-mediated drug interactions.

Prediction of Drug-Drug Interactions with Crizotinib as the CYP3A Substrate Using a Physiologically Based Pharmacokinetic Model.

An orally available multiple tyrosine kinase inhibitor, crizotinib (Xalkori), is a CYP3A substrate, moderate time-dependent inhibitor, and weak inducer. The main objectives of the present study were to: 1) develop and refine a physiologically based pharmacokinetic (PBPK) model of crizotinib on the basis of clinical single- and multiple-dose results, 2) verify the crizotinib PBPK model from crizotinib single-dose drug-drug interaction (DDI) results with multiple-dose coadministration of ketoconazole or rifampin, and 3) apply the crizotinib PBPK model to predict crizotinib multiple-dose DDI outcomes. We also focused on gaining insights into the underlying mechanisms mediating crizotinib DDIs using a dynamic PBPK model, the Simcyp population-based simulator. First, PBPK model-predicted crizotinib exposures adequately matched clinically observed results in the single- and multiple-dose studies. Second, the model-predicted crizotinib exposures sufficiently matched clinically observed results in the crizotinib single-dose DDI studies with ketoconazole or rifampin, resulting in the reasonably predicted fold-increases in crizotinib exposures. Finally, the predicted fold-increases in crizotinib exposures in the multiple-dose DDI studies were roughly comparable to those in the single-dose DDI studies, suggesting that the effects of crizotinib CYP3A time-dependent inhibition (net inhibition) on the multiple-dose DDI outcomes would be negligible. Therefore, crizotinib dose-adjustment in the multiple-dose DDI studies could be made on the basis of currently available single-dose results. Overall, we believe that the crizotinib PBPK model developed, refined, and verified in the present study would adequately predict crizotinib oral exposures in other clinical studies, such as DDIs with weak/moderate CYP3A inhibitors/inducers and drug-disease interactions in patients with hepatic or renal impairment.

Improved dissolution and absorption of ketoconazole in the presence of organic acids as pH-modifiers.

Formulation development of poorly water-soluble compounds can be challenging because of incomplete dissolution that causes low and variable bioavailability. Enhancing compound solubility is important and many techniques have been investigated to that end, but they require specific materials and machinery. This study investigates the incorporation of a pH-modifier as a method to increase compound solubility and uses ketoconazole (KZ), which is weakly basic (pKa: 6.5), as a model compound. Organic acids are effective pH-modifiers and are generally used in pharmaceutical industries. We successfully obtained granules containing variable organic acids (KZ/acid granule) using a high-shear mixer. Dissolution tests of the KZ/acid granule resulted in highly enhanced solubility under non-sink conditions. Adding water-soluble acids, such as citric acid (CA) and tartaric acid, resulted in more than 8-fold higher dissolution at pH 6.0 compared to that of KZ only. The granules containing citric acid (KZ/CA granule) improved the dissolution of KZ after oral administration to rats under low gastric acid conditions, where the bioavailability of the KZ/CA granules at elevated gastric pH was comparable with that of KZ only at gastric acidic pH. The incorporation of organic acids would result in effective therapeutic outcomes independent of gastric pH in patients. In addition, higher bioavailability of KZ was observed after oral administration of KZ/CA granules under gastric acidic pH conditions than that of KZ alone. Thus, CA improved the dissolution and absorption rate of KZ after oral administration.

Quantitative determination of ketoconazole by UPLC-MS/MS in human plasma and its application to pharmacokinetic study.

In this study, a simple, rapid and sensitive ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method is described for determination of ketoconazole (KTZ) in human plasma samples using carbamazepine as the internal standard (IS). Sample preparation was accomplished through one-step liquid-liquid extraction by ethyl acetate, and chromatographic separation was performed on an Acquity BEH C18 column (2.1 mm×50 mm, 1.7 µm) with gradient profile at a flow of 0.45 mL/min. Mass spectrometric analysis was performed using a QTrap5500 mass spectrometer coupled with an electro-spray ionization (ESI) source in the positive ion mode. The MRM transition of m/z 531.2→489.3 was used to quantify for KTZ. The linearity of this method was found to be within the concentration range of 5-15 000 ng/mL for KTZ in human plasma. Only 1.5 min was needed for an analytical run. The method herein described was superior to previous methods and was successfully applied to the pharmacokinetic study of KTZ in healthy Chinese volunteers after oral administration.

Simultaneous determination of probe drugs, metabolites, inhibitors and inducer in human plasma by liquid chromatography/tandem mass spectrometry and its application to pharmacokinetic study.

Cytochrome P450 3A4 (CYP3A4) and UDP-glucuronosyltransferase 1A1 (UGT1A1) are important enzymes responsible for the metabolism of many xenobiotics. To investigate their induction and inhibition properties, administering probe drugs and monitoring their concentration in plasma under the effects of inducers/inhibitors is the gold standard method. A rapid and sensitive liquid chromatography-tandem mass spectrometry method was developed for simultaneous quantification of midazolam, raltegravir (probe drugs for CYP3A4 and UGT1A1), their major metabolites, 1'-hydroxymidazolam, 1'-hydroxymidazolam glucuronide and raltegravir glucuronide, rifampicin (inducer), ritonavir and ketoconazole (inhibitors). Analytes were extracted from 100µl of plasma using solid-phase extraction followed by chromatographic separation on a reversed-phase C18 column (50mm×2.1mm, particle size 1.8µm). The mass spectrometer was operated under positive ionization mode. Excellent linearity (r(2)≥0.995) was achieved for all. The method was validated and found to be accurate (88-111%), precise (CV%<13) and selective. Matrix effect was acceptable (88-118%) and analytes recovery was reproducible (60-95%). Analytes in plasma were also found to be stable in the autosampler (6°C for 48h) and after two freeze-thaw cycles. We have developed a robust analytical method to simultaneously quantify probes, inducer and inhibitor of important drug metabolism enzymes. The method was successfully applied in a clinical study to investigate the degree of induction and inhibition of CYP3A4 and UGT1A1 among ethnic groups in Singapore.

Differential effects of ketoconazole, itraconazole and voriconazole on the pharmacokinetics of imatinib and its main metabolite GCP74588 in rat.

The aim of the study was to develop a high performance liquid chromatography method for simultaneous determination of imatinib and CGP74588 in rat serum and study the inhibition effects of ketoconazole, itraconazole and voriconazole on pharmacokinetics of imatinib and CGP74588 in rats. In our study, we found that ketoconazole caused a significant increase (63.4%) in the AUC of imainib and a 28.8% increase in Cmax, which was greater than that of itraconazole but lower than that of voriconazole. When co-administered with voriconazole, pharmacokinetic parameters of imatinib were not significantly altered except for a 36.8% increase in the Cmax of imtinib. The Cmax of CGP74588 was decreased by 55.8% and AUC(0-∞) 49.7%, while the Vz/F and CLz/F values were increased by 1.7-fold and 1.1-fold, respectively. Itraconazole did not significantly influence the pharmacokinetic parameters of imatinib and CGP74588. The difference may be related to the different variation of inhibition sites of the three azole antifungal agents on CYP3A4 and P-gp. In clinical, when imatinib was co-administrated with ketoconazole or voriconazole, dose adjustment of imatinib should be taken into account.

Pharmacokinetic drug interactions involving vortioxetine (Lu AA21004), a multimodal antidepressant.

BACKGROUND AND OBJECTIVE: The identification and quantification of potential drug-drug interactions is important for avoiding or minimizing the interaction-induced adverse events associated with specific drug combinations. Clinical studies in healthy subjects were performed to evaluate potential pharmacokinetic interactions between vortioxetine (Lu AA21004) and co-administered agents, including fluconazole (cytochrome P450 [CYP] 2C9, CYP2C19 and CYP3A inhibitor), ketoconazole (CYP3A and P-glycoprotein inhibitor), rifampicin (CYP inducer), bupropion (CYP2D6 inhibitor and CYP2B6 substrate), ethinyl estradiol/levonorgestrel (CYP3A substrates) and omeprazole (CYP2C19 substrate and inhibitor). METHODS: The ratio of central values of the test treatment to the reference treatment for relevant parameters (e.g., area under the plasma concentration-time curve [AUC] and maximum plasma concentration [C max]) was used to assess pharmacokinetic interactions. RESULTS: Co-administration of vortioxetine had no effect on the AUC or C max of ethinyl estradiol/levonorgestrel or 5'-hydroxyomeprazole, or the AUC of bupropion; the 90 % confidence intervals for these ratios of central values were within 80-125 %. Steady-state AUC and C max of vortioxetine increased when co-administered with bupropion (128 and 114 %, respectively), fluconazole (46 and 15 %, respectively) and ketoconazole (30 and 26 %, respectively), and decreased by 72 and 51 %, respectively, when vortioxetine was co-administered with rifampicin. Concomitant therapy was generally well tolerated; most adverse events were mild or moderate in intensity. CONCLUSION: Dosage adjustment may be required when vortioxetine is co-administered with bupropion or rifampicin.

Implication of free cholesterol in LC-MS response enhancement.

BACKGROUND: In the context of matrix effects in bioanalytical LC-MS/MS, a speculative link between free cholesterol, the recoveries of the compound from three common extraction procedures, and response enhancement was qualitatively investigated. RESULTS: Injections on-column of cholesterol both in solution and extracts, in conjunction with post-column infusion of three representative drugs, reveal a direct role in pronounced response enhancement for two out of three analytes, under one set of LC-MS/MS conditions, for the majority of typical plasma extraction procedures, where electrospray-based gaseous ion generation is used. CONCLUSION: Cholesterol has been shown to have a strong association with LC-MS/MS response enhancement and ideally should be monitored during method development, reinforcing the reasoning behind minimizing SPE elution volumes and avoiding less selective means of sample preparation.

Ultrasound-enhanced surfactant-assisted dispersive liquid-liquid microextraction and high-performance liquid chromatography for determination of ketoconazole and econazole nitrate in human blood.

A simple and efficient method, based on ultrasound-enhanced surfactant-assisted dispersive liquid-liquid microextraction (UESA-DLLME) followed by high-performance liquid chromatography (HPLC) has been developed for extraction and determination of ketoconazole and econazole nitrate in human blood samples. In this method, a common cationic surfactant, cetyltrimethylammonium bromide (CTAB), was used as dispersant. Chloroform (40 µL) as extraction solvent was added rapidly to 5 mL blood containing 0.068 mg mL(-1) CTAB. The mixture was then sonicated for 2 min to disperse the organic chloroform phase. After the extraction procedure, the mixture was centrifuged to sediment the organic chloroform phase, which was collected for HPLC analysis. Several conditions, including type and volume of extraction solvent, type and concentration of the surfactant, ultrasound time, extraction temperature, pH, and ionic strength were studied and optimized. Under the optimum conditions, linear calibration curves were obtained in the ranges 4-5000 µg L(-1) for ketoconazole and 8-5000 µg L(-1) for econazole nitrate, with linear correlation coefficients for both >0.99. The limits of detection (LODs, S/N = 3) and enrichment factors (EFs) were 1.1 and 2.3 µg L(-1), and 129 and 140 for ketoconazole and econazole nitrate, respectively. Reproducibility and recovery were good. The method was successfully applied to the determination of ketoconazole and econazole nitrate in human blood samples.

Drug-drug interactions between ketoconazole and berberine in rats: pharmacokinetic effects benefit pharmacodynamic synergism.

Ketoconazole (KTZ), a clinical antifungal agent, is a known inhibitor of CYP3A and permeability glycoprotein (P-gp). Berberine (BBR), a natural plant-derived product used for gastroenteritis, is a substrate of P-gp. Recently, a synergistic antifungal effect of KTZ combined with BBR has been revealed. In this study, we performed both in vivo and in vitro experiments to explore whether pharmacokinetic interactions between KTZ and BBR would benefit their pharmacodynamic synergism. After oral co-administration of 10 mg/kg KTZ with 60 mg/kg BBR, the average area under the curve (AUC) and the maximum concentration (C(max) ) for KTZ increased to 215% and 449% (p < 0.05), respectively, in male rats and 157% and 172% (p < 0.05), respectively, in female rats, compared with those administered KTZ alone. Area under the curve and C(max) for BBR increased to 173% and 142%, respectively, compared with those administered BBR alone. After intravenous co-administration of 0.5 mg/kg KTZ and 0.8 mg/kg BBR, the pharmacokinetic properties of KTZ remained the same, but AUC of BBR increased to 254% (p < 0.05) compared with those administered BBR alone. In rat liver microsomes, inhibitory concentration (IC)(50) of BBR inhibiting KTZ depletion was determined to be 103 µm. These resulting pharmacokinetic interactions may benefit their pharmacodynamic synergism to a certain extent.