Comparison of enzyme kinetics of warfarin analyzed by LC–MS/MS QTrap and differential mobility spectrometry

A physiologically-based pharmacokinetic/pharmacodynamic modeling approach for drug-drug-gene interaction evaluation of S-warfarin with fluconazole

Warfarin is a widely used anticoagulant, and its S-enantiomer has higher potency compared to the R-enantiomer. S-warfarin is mainly metabolized by cytochrome P450 (CYP) 2C9, and its pharmacological target is vitamin K epoxide reductase complex subunit 1 (VKORC1). Both CYP2C9 and VKORC1 have genetic polymorphisms, leading to large variations in the pharmacokinetics (PKs) and pharmacodynamics (PDs) of warfarin in the population. This makes dosage management of warfarin difficult, especially in the case of drug-drug interactions (DDIs). This study provides a whole-body physiologically-based pharmacokinetic/PD (PBPK/PD) model of S-warfarin for predicting the effects of drug-drug-gene interactions on S-warfarin PKs and PDs. The PBPK/PD model of S-warfarin was developed in PK-Sim and MoBi. Drug-dependent parameters were obtained from the literature or optimized. Of the 34 S-warfarin plasma concentration-time profiles used, 96% predicted plasma concentrations within twofold range compared to observed data. For S-warfarin plasma concentration-time profiles with CYP2C9 genotype, 364 of 386 predicted plasma concentration values (~94%) fell within the twofold of the observed values. This model was tested in DDI predictions with fluconazole as CYP2C9 perpetrators, with all predicted DDI area under the plasma concentration-time curve to the last measurable timepoint (AUClast) ratio within twofold of the observed values. The anticoagulant effect of S-warfarin was described using an indirect response model, with all predicted international normalized ratio (INR) within twofold of the observed values. This model also incorporates a dose-adjustment method that can be used for dose adjustment and predict INR when warfarin is used in combination with CYP2C9 perpetrators.

Relationships, Current Issues, Safety and Efficacy of Oral Anticoagulation in Cancer Patients with Atrial Fibrillation

A relationship between malignancy and impaired hemostasis has been proven, and balancing clotting and bleeding risks can be challenging. Half of cancer patients with atrial fibrillation (AF) do not receive any oral anticoagulation (OAC). Using PubMed on the relationship between cancer and AF and their association with hemostasis, targeting studies comparing vitamin K antagonists (VKAs) and direct OAC (DOAC) strategies in AF cancer patients, three RCTs (>3000 patients) and eight observational studies (>250,000 patients) comparing different OACs were retrieved. The VKA prescribed was always warfarin. Dabigatran was the only DOAC not analyzed in the RCTs but the most used in non-randomized studies, whereas edoxaban-treated patients were the majority in the RCTs. Overall, the DOAC patients showed similar or lower rates of efficacy (thromboembolic) and safety (bleeding) outcomes compared to the VKA patients. DOACs are subject to fewer interactions with antineoplastic agents. DOACs may be preferable to VKAs as a thromboembolic prophylaxis in cancer patients with non-valvular AF.

Predicting In Vivo Target Occupancy (TO) Profiles via Physiologically Based Pharmacokinetic-TO Modeling of Warfarin Pharmacokinetics in Blood: Importance of Low Dose Data and Prediction of Stereoselective Target Interactions

Warfarin is well recognized for its high-affinity and capacity-limited binding to the pharmacological target and undergoes target-mediated drug disposition. Here, we developed a physiologically based pharmacokinetic (PBPK) model that incorporated saturable target binding and other reported hepatic disposition components of warfarin. The PBPK model parameters were optimized by fitting to the reported blood pharmacokinetic (PK) profiles of warfarin with no stereoisomeric separation after oral dosing of racemic warfarin (0.1, 2, 5, or 10 mg) using the Cluster Gauss-Newton method (CGNM). The CGNM-based analysis yielded multiple "accepted" sets for six optimized parameters, which were then used to simulate the warfarin blood PK and in vivo target occupancy (TO) profiles. When further analyses examined the impact of dose selection on uncertainty in parameter estimation by the PBPK modeling, the PK data from 0.1 mg dose (well below target saturation) was important in practically identifying the target binding-related parameters in vivo. When stereoselective differences were incorporated for both hepatic disposition and target interactions, our PBPK modeling predicted that R-warfarin (of slower clearance and lower target affinity than S-warfarin) contributes to TO prolongation after oral dosing of racemic warfarin. Our results extend the validity of the approach by which the PBPK-TO modeling of blood PK profiles can yield TO prediction in vivo (applicable to the drugs with targets of high affinity and abundance and limited distribution volume via nontarget interactions). Our findings support that model-informed dose selection and PBPK-TO modeling may aid in TO and efficacy assessment in preclinical and clinical phase 1 studies. SIGNIFICANCE STATEMENT: The current physiologically based pharmacokinetic modeling incorporated the reported hepatic disposition components and target binding of warfarin and analyzed the blood pharmacokinetic (PK) profiles from varying warfarin doses, practically identifying target binding-related parameters in vivo. By implementing the stereoselective differences between R- and S-warfarin, our analysis predicted the role of R-warfarin in prolonging overall target occupancy. Our results extend the validity of analyzing blood PK profiles to predict target occupancy in vivo, which may guide efficacy assessment.

A genome-wide association study of plasma concentrations of warfarin enantiomers and metabolites in sub-Saharan black-African patients

Diversity in pharmacogenomic studies is poor, especially in relation to the inclusion of black African patients. Lack of funding and difficulties in recruitment, together with the requirement for large sample sizes because of the extensive genetic diversity in Africa, are amongst the factors which have hampered pharmacogenomic studies in Africa. Warfarin is widely used in sub-Saharan Africa, but as in other populations, dosing is highly variable due to genetic and non-genetic factors. In order to identify genetic factors determining warfarin response variability, we have conducted a genome-wide association study (GWAS) of plasma concentrations of warfarin enantiomers/metabolites in sub-Saharan black-Africans. This overcomes the issue of non-adherence and may have greater sensitivity at genome-wide level, to identify pharmacokinetic gene variants than focusing on mean weekly dose, the usual end-point used in previous studies. Participants recruited at 12 outpatient sites in Uganda and South Africa on stable warfarin dose were genotyped using the Illumina Infinium H3Africa Consortium Array v2. Imputation was conducted using the 1,000 Genomes Project phase III reference panel. Warfarin/metabolite plasma concentrations were determined by high-performance liquid chromatography with tandem mass spectrometry. Multivariable linear regression was undertaken, with adjustment made for five non-genetic covariates and ten principal components of genetic ancestry. After quality control procedures, 548 participants and 17,268,054 SNPs were retained. CYP2C9*8, CYP2C9*9, CYP2C9*11, and the CYP2C cluster SNP rs12777823 passed the Bonferroni-adjusted replication significance threshold (p < 3.21E-04) for warfarin/metabolite ratios. In an exploratory GWAS analysis, 373 unique SNPs in 13 genes, including CYP2C9*8, passed the Bonferroni-adjusted genome-wide significance threshold (p < 3.846E-9), with 325 (87%, all located on chromosome 10) SNPs being associated with the S-warfarin/R-warfarin outcome (top SNP rs11188082, CYP2C19 intron variant, p = 1.55E-17). Approximately 69% of these SNPs were in linkage disequilibrium (r² > 0.8) with CYP2C9*8 (n = 216) and rs12777823 (n = 8). Using a pharmacokinetic approach, we have shown that variants other than CYP2C9*2 and CYP2C9*3 are more important in sub-Saharan black-Africans, mainly due to the allele frequencies. In exploratory work, we conducted the first warfarin pharmacokinetics-related GWAS in sub-Saharan Africans and identified novel SNPs that will require external replication and functional characterization before they can be considered for inclusion in warfarin dosing algorithms.

Investigating the uncertainty of prediction accuracy for the application of physiologically based pharmacokinetic models to animal-free risk assessment of cosmetic ingredients

Physiologically based pharmacokinetic (PBPK) models are considered useful tools in animal-free risk assessment. To utilize PBPK models for risk assessment, it is necessary to compare their reliability with in vivo data. However, obtaining in vivo pharmacokinetics data for cosmetic ingredients is difficult, complicating the utilization of PBPK models for risk assessment. In this study, to utilize PBPK models for risk assessment without accuracy evaluation, we proposed a novel concept-the modeling uncertainty factor (MUF). By calculating the prediction accuracy for 150 compounds, we established that using in vitro data for metabolism-related parameters and limiting the applicability domain increase the prediction accuracy of a PBPK model. Based on the 97.5th percentile of prediction accuracy, MUF was defined at 10 for the area under the plasma concentration curve and 6 for C_max. A case study on animal-free risk assessment was conducted for bisphenol A using these MUFs. As this study was conducted mainly on pharmaceuticals, further investigation using cosmetic ingredients is pivotal. However, since internal exposure is essential in realizing animal-free risk assessment, our concept will serve as a useful tool to predict plasma concentrations without using in vivo data.

Simultaneous Characterization and Determination of Warfarin and Its Hydroxylation Metabolites in Rat Plasma by Chiral Liquid Chromatography-Tandem Mass Spectrometry

Warfarin is extensively used for venous thromboembolism and other coagulopathies. In clinical settings, warfarin is administered as a mixture of S- and R-warfarin, and both enantiomers are metabolized by multiple cytochrome P450 enzymes into many hydroxylation metabolites. Due to the high degree of structural similarity of hydroxylation metabolites, their profile possesses significant challenges. The previous methods generally suffer from lacking baseline resolution and/or involving complex analysis processes. To overcome this limitation, a sensitive and specific chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to simultaneously identify warfarin and hydroxywarfarins enantiomers. Chromatographic separation was achieved on a HYPERSIL CHIRAL-OT column. The mass spectrometric detection was carried out in negative ion MRM mode with electrospray ionization source. The optimized method exhibited satisfactory within-run and between-run accuracy and precision with lower limit of quantification (LLOQ) of 10.0 ng/mL and 1.0 ng/mL for warfarin and 7-, 10(R)-OH-warfarin enantiomers, respectively. Linear responses of warfarin enantiomers and 7-, and 10(R)-OH-warfarin enantiomers in rat plasma were observed over the range of 10.0–8000 ng/mL, and 1.00–800 ng/mL, respectively. The analytes were shown to be stable in various experimental conditions in rat plasma. Protein precipitation was used in sample preparation without a matrix effect. This method was successfully applied to pharmacokinetic study for quantitating the concentrations of S/R-warfarin, S/R-7-OH-warfarin, and S/R-10(R)-OH-warfarin and relatively quantitating 3′-, 4-, 6-, and 8-OH warfarin enantiomers in rat plasma.

Pharmacogenomics Informs Cardiovascular Pharmacotherapy

Precision medicine exemplifies the emergence of personalized treatment options which may benefit specific patient populations based upon their genetic makeup. Application of pharmacogenomics requires an understanding of how genetic variations impact pharmacokinetic and pharmacodynamic properties. This particular approach in pharmacotherapy is helpful because it can assist in and improve clinical decisions. Application of pharmacogenomics to cardiovascular pharmacotherapy provides for the ability of the medical provider to gain critical knowledge on a patient's response to various treatment options and risk of side effects.

An integrated strategy for the establishment of a protoberberine alkaloid profile: Exploration of the differences in composition between Tinosporae radix and Fibraurea caulis

INTRODUCTION

Accurate species and content identification of major active components in herbals are the guarantee of the safety and effectiveness for medical and commodity purposes.

OBJECTIVES

In this study, an integrated strategy used to establish the protoberberine alkaloid profile was applied to explore the differences in composition between the pieces of Tinosporae radix and Fibraurea caulis, both of which had morphological similarities.

MATERIALS AND METHODS

First, an in-house library including possible protoberberine alkaloids based on different substituents was predicted by systematic literature survey. Meanwhile, diagnostic fragments of protoberberine alkaloids were investigated using the corresponding standards. Second, ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) was used to obtain multidimensional mass spectral data. Then, the identifications were confirmed by targeted filter of the acquired data based on the library.

RESULTS

As a result, 10 protoberberine alkaloid molecules including 46 isomers were identified or characterised. The qualitative distribution and relative content of protoberberine alkaloids revealed the fundamental difference between Tinosporae radix and Fibraurea caulis. 25 alkaloids were present in both herbals, while five compounds were detected only in Tinosporae radix. Furthermore, the contents of four alkaloids in Tinosporae radix were significantly higher than those in its adulterant, Fibraurea caulis.

CONCLUSION

The five unique ingredients in Tinosporae radix can be used as a better indicator for distinguishing the pieces of Tinosporae radix and Fibraurea caulis. The protoberberine alkaloid profile established in this study can be applied to quality evaluation of the two herbals or other herbals containing major protoberberine alkaloids.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for warfarin derivatives and their application for the determination of warfarin in human serum

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), 4'-bromowarfarin (BWF), 4'-nitrowarfarin (NWF) and 4'-methylwarfarin (MWF) (MIP_WF, MIP_CWF, MIP_BWF, MIP_NWF and MIP_MWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate as a functional monomer and crosslinker, respectively, by multi-step swelling and polymerization. The retention and molecular-recognition properties of those MIPs were evaluated in HILIC, and reversed- and normal-phase modes. According to ¹H NMR studies, one-to-three complex formation of one WF or CWF molecule with three 4-VPY molecules occurred. Via computational approaches, the intermolecular interaction modes and energies between WF derivatives and 4-VPYs were evaluated by semi-empirical quantum chemistry methods and density functional theory calculations. Three major possible hydrogen bonding interaction modes were identified: the interactions between the 4-hydroxy group, α-proton (methylene C-H) and α-proton (methyl C-H) of the WF derivative and the nitrogen atoms of 4-VPYs. In HILIC and normal-phase modes, the interaction energies showed satisfactory correlations with the retention factors of the WF derivatives. In reversed-phase mode, the retention factors of the WF derivatives were described by the hydrophobicity and the acidity of the 4-hydroxy groups of the WF derivatives. These results demonstrate that three hydrogen bonding interactions in HILIC and normal-phase modes, and hydrogen bonding or ionic interactions and hydrophobic interactions in reversed-phase mode play important roles in the retention and molecular-recognition of the WF derivatives on MIPs. Furthermore, MIP_BWF was successfully applied to the determination of WF in human serum by column-switching LC with high accuracy, precision and selectivity and without template-leakage problems.

Enantioseparation of warfarin derivatives on molecularly imprinted polymers for (S)- and (R)-chlorowarfarin

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), (S)-CWF and (R)-CWF (MIP_WF, MIP_CWF, MIP_(S)-_CWF and MIP_(R)-_CWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate (EDMA) as a functional monomer and a crosslinker, respectively, by multi-step swelling and polymerization. The molar ratio of a template molecule, 4-VPY to EDMA was 6:18:25 or 4:18:25. The retention and molecular recognition properties of MIP_WF and MIP_CWF were evaluated using a mixture of sodium phosphate buffer or ammonium formate and acetonitrile in reversed-phase LC. WF and CWF on these MIPs gave the maximal retentions at mobile phase pH 7, and those retentions were decreased with an increase of acetonitrile content. The retention and imprinting factors were in the order of WF < CWF < 4'-bromowarfarin (BWF) on MIP_WF and MIP_CWF in neutral mobile phases. On the other hands, in acidic mobile phases the retention factors were in the same order with those in neutral mobile phases, while the imprinting factors of WF and CWF were higher on the respective MIPs. These results suggest that ionic or hydrogen bonding interactions, hydrophobic interactions and π-π interactions could work for the retention and molecular recognition of WF, CWF and BWF on these MIPs in a reversed-phase mode. Furthermore, MIP_(S)-_CWF and MIP_(R)-_CWF could separate WF, CWF and BWF enantiomers in acidic mobile phases.

Simultaneous determination of warfarin and 7-hydroxywarfarin in rat plasma by HPLC-FLD

In this study, high-performance liquid chromatography with fluorescence detection (HPLC-FLD) has been used for the first time, for direct determination of warfarin and its major metabolite, 7-hydroxywarfarin, in rat plasma. The simple and sensitive method was developed using Fortis® reversed-phase diphenyl column (150 × 4.6 mm, 3 μm) and a mobile phase composed of phosphate buffer (25 mmol L-1)/methanol/acetonitrile (70:20:10, V/V/V), adjusted to pH 7.4, at a flow rate of 0.8 mL min-1. The diphenyl chemistry of the stationary phase provided a unique selectivity for separating the structurally related aromatic analytes, warfarin and 7-hydroxywarfarin, allowing their successful quantification in the complex plasma matrix. The method was linear over the range 0.01-25 μg mL-1, for warfarin and 7-hydroxywarfarin, and was found to be accurate, precise and selective in accordance with US FDA guidance for bioanalytical method validation. The method was sensitive enough to quantify 0.01 μg mL-1 of warfarin and 7-hydroxywarfarin (LLOQ) using only 100 μL of plasma. The applicability of this method was demonstrated by analyzing samples obtained from rats after oral administration of a single warfarin dose, and studying warfarin and 7-hydroxywarfarin pharmacokinetics.

Drug-Drug Interactions of 257 Antineoplastic and Supportive Care Agents With 7 Anticoagulants: A Comprehensive Review of Interactions and Mechanisms

Data on drug–drug interactions (DDI) of antineoplastic drugs with anticoagulants is scarce. We aim to evaluate factors associated with DDI of antineoplastic and supportive care drugs with anticoagulants resulting in modification of pharmacokinetics of these last mentioned. A literature review on DDI databases and summaries of products characteristics (SmPC) was done. Drug–drug interactions of 257 antineoplastic and supportive care drugs with direct oral anticoagulants (DOACs), warfarin, enoxaparin, or fondaparinux were categorized as no clinically significant expected DDI, potentially weak DDI, potentially clinically significant DDI, and recommendation against coadministration. Logistic regression models were performed to analyze the association between the dependent variable potentially clinically significant interaction/recommendation against coadministration and the mechanisms of DDI. Of the 1799 associations, 84.4% were absence of DDI, 3.6% potentially weak DDI, 10.2% potentially clinically relevant DDI, and 2.0% recommendation against coadministration. Warfarin has higher DDI potential than other anticoagulants. Enoxaparin and fondaparinux have fewer DDI than others. There was no difference between DOACs. Drug–drug interactions with apixaban and rivaroxaban was independently associated with the absence of CYP3A4 competition, P-glycoprotein inhibition, CYP3A4 induction, and drug class of tyrosine kinase inhibitors. Drug–drug interactions with dabigatran and edoxaban was associated with inhibition of P-glycoprotein and tyrosine kinase inhibitors. Warfarin, induction of CYP3A4, and inhibition of CYP2C9. Enoxaparin and fondaparinux, only tyrosine kinase inhibitors. Direct oral anticoagulants did not differ regarding DDI with antineoplastic agents. Warfarin presented more DDI than other anticoagulants. P-glycoprotein inhibition and CYP3A4 induction were independently associated with DDI of antineoplastic agents with DOACs.

In vitro metabolism of olaparib in liver microsomes by liquid chromatography/electrospray ionization high-resolution mass spectrometry

RATIONALES

Olaparib is a Poly (ADP-ribose) Polymerase (PARP) inhibitor which has been developed as an anti-cancer agent. The purpose of this study was to characterize the metabolites of olaparib from liver microsomes and to reveal the interspecies differences between animals and humans.

METHODS

Olaparib (20 μM) was incubated with different species of liver microsomes at 37°C for 1 h in the presence of NADPH. The incubation samples were analyzed by liquid chromatography/electrospray ionization high-resolution mass spectrometry (LC/ESI-HRMS) operated in positive ion mode. The metabolites were characterized by accurate masses, MS² spectra and retention times.

RESULTS

A total of 12 metabolites were detected and the structures of the metabolites were characterized based on their accurate masses, fragment ions and retention times. Four metabolites, i.e., M1, M10, M11 and M12, were unambiguously identified by using reference standards. The metabolic pathways of olaparib included hydroxylation, bis-hydroxylation, hydrolysis, dealkylation, dehydrogenation, and alcohol oxidation.

CONCLUSIONS

Compared with animal species, no human-specific metabolite was found in HLM. Dog also had a closer metabolic profile to humans. This study will be helpful for a better understanding of the species difference in pharmacokinetics/pharmacodynamics.

Potential Antimigraine Effects of Warfarin: An Exploration of Biological Mechanism with Survey of Patients

Case reports suggest a link between anticoagulant use and improved migraine symptoms, and a role for platelet-induced cerebral vasoconstriction in migraine pathobiology. Hence, we investigated the mechanism by which warfarin may affect migraine symptoms and whether there is a change in migraine symptomology in patients initiating oral anticoagulants, most commonly warfarin. The effects of warfarin on human platelet aggregation and secretion as well as platelet-induced rat cerebral artery vasoconstriction were studied. A survey of migraine and symptom change after starting or stopping oral anticoagulants was also conducted. Warfarin inhibited platelet aggregation and 5-hydroxytryptamine (5-HT) secretion in a concentration-dependent manner. Warfarin-inhibited platelet secretion products constricted middle cerebral arteries from male but not from female rats. For the survey, patient demographic information, migraine and medical history, and Migraine Disability Assessment Score (MIDAS) changes were collected. Out of 175 consenting, 40 respondents met the criteria for migraine and completed the survey. A total of 11 patients reported migraine symptom change, all coinciding with starting warfarin. Of those having symptom and MIDAS improvement, most were female with migraines with aura, whereas those worsening were male with fewer having migraine with aura. Of those reporting migraine symptom change with warfarin, female sex may be associated with improved MIDAS, and those experiencing an aura component are more likely to report a symptom change. Warfarin-mediated symptom improvement in females may occur due to inhibition of platelet 5-HT secretion and a lower sensitivity of female cerebral blood vessels to platelet-derived 5-HT-induced vasoconstriction.

Metabolism of vesatolimod in rat, dog, and human liver microsomes: Metabolic stability assessment, metabolite identification, and interspecies comparison

Vesatolimod (GS-9620) is an agonist of toll-like receptor (TLR7) 7, which has been developed as an anti-hepatitis B virus (HBV) agent. The focus of the present study is on the metabolic stability evaluation and metabolite identification of GS-9620 in rat, dog, and human liver microsomes, as well as interspecies comparison. The average observed in vitro T_1/2 values were 3.06, 13.06, and 15.56 minutes in rat, dog, and human liver microsomes, respectively. The findings suggested that GS-9620 was rapidly metabolized in the presence of reductive nicotinamide adenine dinucleotide phosphate (NADPH) in rat liver microsomes (RLM), and moderately metabolized in dog liver microsomes (DLM) and human liver microsomes (HLM). Subsequently, the metabolites were characterized using an ultra-high performance liquid chromatography coupled with linear ion trap orbitrap tandem mass spectrometer (UHPLC-LTQ-Orbitrap-MS) with dd-MS² on-line data acquisition mode. Under the current conditions, a total of 18 metabolites were detected and their identities were proposed by comparing their accurate masses, fragmental ions, and retention times with those of GS-9620. Three metabolites (M2, M4, and M18) were authentically identified by using reference standards. In RLM, 16 metabolites were identified with M2 being the most abundant metabolite. M4, M5, and M9 were rat-specific. In DLM, 12 minor metabolites were identified with a dog-specific metabolite (M6). In HLM, GS-9620 showed similar metabolic profiles to that in DLM, and 11 minor metabolites were detected with M12 being human-specific. Based on the identified metabolites, the metabolic pathways of GS-9620 were proposed, including hydroxylation, bis-hydroxylation, dehydrogenation, and oxidative deamination.

Separation and simultaneous quantitation of PGF2α and its epimer 8-iso-PGF2α using modifier-assisted differential mobility spectrometry tandem mass spectrometry

Because many therapeutic agents are contaminated by epimeric impurities or form epimers as a result of metabolism, analytical tools capable of determining epimers are increasingly in demand. This article is a proof-of-principle report of a novel DMS-MS/MS method to separate and simultaneously quantify epimers, taking PGF2α and its 8-epimer, 8-iso-PGF2α, as an example. Good accuracy and precision were achieved in the range of 10-500 ng/mL with a run time of only 1.5 min. Isopropanol as organic modifier facilitated a good combination of sensitivity and separation. The method is the first example of the quantitation of epimers without chromatographic separation.

Health risks associated with the pharmaceuticals in wastewater

The overwhelming population growth in recent decades and water crisis along with limited and uneven geographical distribution of fresh water resources is a growing challenge for the economic and human development. Wastewater reclamation and use could be an alternative for intact water sources and a promising solution to water scarcity and unequal distribution. However, wastewater is a double-edged resource both as an accessible water source for food production and human usage and concurrently may carry uncharacterized content with unknown toxicological profile causing acute or long-term health risks. Pharmaceuticals, cosmeceuticals, nanomaterials and their chemical decomposition derivatives found in wastewater are not well known in many cases. Their unknown toxicity, teratogenicity and carcinogenicity profile associated with lack of monitoring and control measures impose a significant hazard risk on the public health. This paper reviews the evidence on the health risks associated with the wastewater use for irrigated food production and the imposed risk on the end consumers mainly from pharmaceutical industry and related research facilities. Then, we suggest an applied framework for planning and policy-making to mitigate the health risks and optimally employ reclaimed wastewater for human purposes.

Detection of the anticoagulant drug warfarin by palladium complexes

This work illustrates the application of palladium complexes in the significant sensing of warfarin, a commercial anticoagulant drug, not only in organic solvents but also in aqueous medium.

The Active Metabolite of Warfarin (3'-Hydroxywarfarin) and Correlation with INR, Warfarin and Drug Weekly Dosage in Patients under Oral Anticoagulant Therapy: A Pharmacogenetics Study

Objectives

Warfarin oral anticoagulant therapy (OAT) requires regular and frequent drug adjustment monitored by INR. Interindividual variability, drug and diet interferences, and genetics (VKORC1 and CYP2C9) make the maintenance/reaching of stable INR a not so easy task. HPLC assessment of warfarin/enantiomers was suggested as a valid monitoring-tool along with INR, but definite results are still lacking. We evaluated possible correlations between INR, warfarin/3’-hydroxywarfarin, and drug weekly dosage aimed at searching novel alternatives to OAT monitoring. VKORC1/CYP2C9 pharmacogenetics investigation was performed to account for the known influence on warfarin homeostasis.

Methods

133 OAT patients were recruited and assessed for warfarin/3’-hydroxywarfarin serum levels (HPLC), INR, and VKORC1 and CYP2C9 genotypes. A subgroup of 52 patients were monitored in detail (5 consecutive controls; c0-c4) till the target INR was reached. Correlation analyses were performed in both groups

Results

In the whole OAT group both warfarin and 3’-hydroxywarfarin correlate with INR at comparable degree (r² = 0.0388 and 0.0362 respectively). Conversely, warfarin weekly dosage better correlates with warfarin than with 3’-hydroxywarfarin (r² = 0.0975 and r² = 0.0381 respectively), but considering together warfarin plus 3’-hydroxywarfarin the correlation strongly increased (r² = 0.1114; p<0.0001). Interestingly, 3’-hydroxywarfarin reached a strong correlation at c4 respect to warfarin (r² = 0.2157 and r² = 0.0549; p = 0.0005 and p = 0.0944 respectively) seeming less affected by drug adjustments in the subgroup of 52 patients who started OAT. The multivariate analyses aimed at estimating the true contribution of 3’-hydroxywarfarin on INR value ascribed it the unique significant value (p = 0.0021) in spite of warfarin who lost association. The pharmacogenetics studies confirmed that patients carrying the VKORC1 variant-allele required lower warfarin maintenance dosage and that the combination of VKORC1 and CYP2C9 yielded a warfarin responsive index (WRI) inversely related to the number variant alleles

Conclusion

Our results overall suggest that 3’-hydroxywarfarin monitoring could be of great advantage in INR monitoring respect to classical warfarin assessment showing significant contribution also in multivariate analysis. Therefore, additional active metabolites should be recognized and investigated as novel useful indicators.

Mechanism of Drug-Drug Interactions Between Warfarin and Statins

The anticoagulant drug warfarin and the lipid-lowering statin drugs are commonly co-administered to patients with cardiovascular diseases. Clinically significant drug-drug interactions (DDIs) between these drugs have been recognized through case studies for many years, but the biochemical mechanisms causing these interactions have not been explained fully. Previous theories include kinetic alterations in cytochrome P-450-mediated drug metabolism or disturbances of drug-protein binding, leading to anticoagulant activity of warfarin; however, neither the enantioselective effects on warfarin metabolism nor the potential disruption of drug transporter function have been well investigated. This study investigated the etiology of the DDIs between warfarin and statins. Liquid chromatography-mass spectrometry methods were developed and validated to quantify racemic warfarin, 6 of its hydroxylated metabolites, and pure enantiomers of warfarin; these methods were applied to study the role of different absorption, distribution, metabolism, and excretion properties, leading to DDIs. Plasma protein binding displacement of warfarin was performed in the presence of statins using equilibrium dialysis method. Substrate kinetics of warfarin and pure enantiomers were performed with human liver microsomes to determine the kinetic parameters (Km and Vmax) for the formation of all 6 hydroxywarfarin metabolites, inhibition of warfarin metabolism in the presence of statins, was determined. Uptake transport studies of warfarin were performed using overexpressing HEK cell lines and efflux transport using human adenocarcinoma colonic cell line cells. Fluvastatin significantly displaced plasma protein binding of warfarin and pure enantiomers; no other statin resulted in significant displacement of warfarin. All the statins that inhibited the formation of 10-hydroxywarfarin, atorvastatin, pitavastatin, and simvastatin were highly potent compared to other statins; in contrast, only fluvastatin was found to be a potent inhibitor of formation of 7-hydroxy warfarin. Uptake and efflux drug transporters do not play any role in these DDIs. The results showed that DDIs between warfarin and statins are primarily caused by cytochrome P-450 inhibition.