Inhibitory effects of amiodarone and its N-deethylated metabolite on human cytochrome P450 activities: prediction of in vivo drug interactions

Clinical Implications of Co-administering Apixaban with Key Interacting Medications

With many available data sources, clinicians need to consider the benefit-risk profile of individual anticoagulants when balancing the need for anticoagulation, including evaluating the risks in patients with comorbidities and potential drug-drug interactions. This narrative review presents clinical data across multiple phases of drug development for the use of apixaban, a selective factor Xa inhibitor, when taken concomitantly with other agents, and evaluates the benefit-risk profile of apixaban with these interacting medications. Key subgroup analyses from the phase 3 ARISTOTLE trial (NCT00412984) are presented using data from patients who received either concomitant inhibitors or inducers of cytochrome P450 3A4 and/or P‑glycoprotein. We also review the available evidence for the use of apixaban in patients with cancer-associated thromboembolism, as well as the use of apixaban in patients with COVID-19.

Effect of CYP2D6, 2C19, and 3A4 Phenoconversion in Drug-Related Deaths

Molecular autopsy is a very important tool in forensic toxicology. However, many determinants, such as co-medication and physiological parameters, should be considered for optimal results. These determinants could cause phenoconversion (PC), a discrepancy between the real metabolic profile after phenoconversion and the phenotype determined by the genotype. This study's objective was to assess the PC of drug-metabolizing enzymes, namely CYP2D6, 2C19, and 3A4, in 45 post-mortem cases where medications that are substrates, inducers, or inhibitors of these enzymes were detected. It also intended to evaluate how PC affected the drug's metabolic ratio (MR) in four cases. Blood samples from 45 cases of drug-related deaths were analyzed to detect and determine drug and metabolite concentrations. Moreover, all the samples underwent genotyping utilizing the HaloPlex Target Enrichment System for CYP2D6, 2C19, and 3A4. The results of the present study revealed a statistically significant rate of PC for the three investigated enzymes, with a higher frequency of poor metabolizers after PC. A compatibility was seen between the results of the genomic evaluation after PC and the observed MRs of venlafaxine, citalopram, and fentanyl. This leads us to focus on the determinants causing PC that may be mainly induced by drug interactions. This complex phenomenon can have a significant impact on the analysis, interpretation of genotypes, and accurate conclusions in forensic toxicology. Nevertheless, more research with more cases in the future is needed to confirm these results.

Impact of amiodarone use on metoprolol concentrations, α-OH-metoprolol concentrations, metoprolol dosing and heart rate: A cross-sectional study

Small studies suggest that amiodarone is a weak inhibitor of cytochrome P450 (CYP) 2D6. Inhibition of CYP2D6 leads to increases in concentrations of drugs metabolized by the enzyme, such as metoprolol. Considering that both metoprolol and amiodarone have β-adrenergic blocking properties and that the modest interaction between the two drugs would result in increased metoprolol concentrations, this could lead to a higher risk of bradycardia and atrioventricular block. The primary objective of this study was to evaluate whether metoprolol plasma concentrations collected at random timepoints from patients enrolled in the Montreal Heart Institute Hospital Cohort could be useful in identifying the modest pharmacokinetic interaction between amiodarone and metoprolol. We performed an analysis of a cross-sectional study, conducted as part of the Montreal Heart Institute Hospital Cohort. All participants were self-described "White" adults with metoprolol being a part of their daily pharmacotherapy regimen. Of the 999 patients being treated with metoprolol, 36 were also taking amiodarone. Amiodarone use was associated with higher metoprolol concentrations following adjustment for different covariates (p = .0132). Consistently, the association between amiodarone use and lower heart rate was apparent and significant after adjustment for all covariates under study (p = .0001). Our results highlight that single randomly collected blood samples can be leveraged to detect modest pharmacokinetic interactions.

Desipramine induces eryptosis in human erythrocytes, an effect blunted by nitric oxide donor sodium nitroprusside and N-acetyl-L-cysteine but enhanced by Calcium depletion

Background: Desipramine a representative of tricyclic antidepressants (TCAs) promotes recovery of depressed patients by inhibition of reuptake of neurotransmitters serotonin (SER) and norepinephrine (NE) in the presynaptic membrane by directly blocking their respective transporters SERT and NET.Aims: To study the effect of desipramine on programmed erythrocyte death (eryptosis) and explore the underlying mechanisms.Methods: Phosphatidylserine (PS) exposure on the cell surface as marker of cell death was estimated from annexin-V-binding, cell volume from forward scatter in flow cytometry. Hemolysis was determined photometrically, and intracellular glutathione [GSH]i from high performance liquid chromatography.Results: Desipramine dose-dependently significantly enhanced the percentage of annexin-V-binding cells and didn´t impact glutathione (GSH) synthesis. Desipramine-induced eryptosis was significantly reversed by pre-treatment of erythrocytes with either nitric oxide (NO) donor sodium nitroprusside (SNP) or N-acetyl-L-cysteine (NAC). The highest inhibitory effect was obtained by using both inhibitors together. Calcium (Ca2+) depletion aggravated desipramine-induced eryptosis. Changing the order of treatment, i.e. desipramine first followed by inhibitors, could not influence the inhibitory effect of SNP or NAC.Conclusion: Antidepressants-caused intoxication can be treated by SNP and NAC, respectively. B) Patients with chronic hypocalcemia should not be treated with tricyclic anti-depressants or their dose should be noticeably reduced.

Strategies for Avoiding Typical Drug-Drug Interactions and Drug-Related Problems in Patients with Vascular Diseases

Background and objectives: Drug-drug interactions and drug-related problems in patients with vascular diseases are common. To date, very few studies have focused on these important problems. The aim of the present study is to investigate the most common drug-drug interactions and DRPs in patients with vascular diseases. Materials and Methods: The medications of 1322 patients were reviewed manually in the time period from 11/2017 to 11/2018; the medications of 96 patients were entered into a clinical decision support system. Potential drug problems were identified, and a read-through consensus was reached between a clinical pharmacist and a vascular surgeon during the clinical curve visits; possible modifications were implemented. The focus was on additional dose adjustment and drug antagonization on drug interactions. Interactions were classified as contraindicated/high-risk combination (drugs must not be combined), clinically serious (interaction can be potentially life-threatening or have serious, possibly irreversible consequences), or potentially clinically relevant and moderate (interaction can lead to therapeutically relevant consequences). Results: A total of 111 interactions were observed. Of these, 6 contraindicated/high-risk combinations, 81 clinically serious interactions, and 24 potentially clinically relevant and moderate interactions were identified. Furthermore, 114 interventions were recorded and categorized. Discontinued use of the drug (36.0%) and drug dose adjustment (35.1%) were the most common interventions. Mostly, antibiotic therapy was continued unnecessarily (10/96; 10.4%), and the adjustment of the dosage to kidney function was overlooked in 40/96; 41.7% of the cases. In the most common cases, a dose reduction was not considered necessary. Here, unadjusted doses of antibiotics were found in 9/96, 9.3% of the cases. Notes for medical professionals summarized information that did not require direct intervention but rather increased attention on the part of the ward doctor. It was usually necessary to monitor laboratory parameters (49/96, 51.0%) or the patients for side effects (17/96, 17.7%), which were expected with the combinations used. Conclusions: This study could help identify problematic drug groups and develop prevention strategies for drug-related problems in patients with vascular diseases. A multidisciplinary collaboration between the different professional groups (clinical pharmacists and surgeons) might optimize the medication process. Collaborative care could have a positive impact on therapeutic outcomes and make drug therapy safer for patients with vascular diseases.

Administration of Secretome Derived from Human Mesenchymal Stem Cells Induces Hepatoprotective Effects in Models of Idiosyncratic Drug-Induced Liver Injury Caused by Amiodarone or Tamoxifen

Drug-induced liver injury (DILI) is one of the leading causes of acute liver injury. While many factors may contribute to the susceptibility to DILI, obese patients with hepatic steatosis are particularly prone to suffer DILI. The secretome derived from mesenchymal stem cell has been shown to have hepatoprotective effects in diverse in vitro and in vivo models. In this study, we evaluate whether MSC secretome could improve DILI mediated by amiodarone (AMI) or tamoxifen (TMX). Hepatic HepG2 and HepaRG cells were incubated with AMI or TMX, alone or with the secretome of MSCs obtained from human adipose tissue. These studies demonstrate that coincubation of AMI or TMX with MSC secretome increases cell viability, prevents the activation of apoptosis pathways, and stimulates the expression of priming phase genes, leading to higher proliferation rates. As proof of concept, in a C57BL/6 mouse model of hepatic steatosis and chronic exposure to AMI, the MSC secretome was administered endovenously. In this study, liver injury was significantly attenuated, with a decrease in cell infiltration and stimulation of the regenerative response. The present results indicate that MSC secretome administration has the potential to be an adjunctive cell-free therapy to prevent liver failure derived from DILI caused by TMX or AMI.

Clinical significance of the rivaroxaban-dronedarone interaction: insights from physiologically based pharmacokinetic modelling

Patients with atrial fibrillation may require rhythm control therapy in addition to anticoagulation therapy for the prevention of stroke. Since 2012, the European Society of Cardiology and European Heart Rhythm Association guidelines have recommended non-vitamin K antagonist oral anticoagulants, including rivaroxaban, for the prevention of stroke in patients with atrial fibrillation. During the same period, these guidelines have also recommended dronedarone or amiodarone as second-line rhythm control agents in certain patients with atrial fibrillation and no contraindications. Amiodarone and dronedarone both strongly inhibit P-glycoprotein, while dronedarone is a moderate and amiodarone a weak inhibitor of cytochrome P450 3A4 (CYP3A4). Based on these data and evidence from physiologically based pharmacokinetic modelling, amiodarone and dronedarone are expected to have similar effects on rivaroxaban exposure resulting from P-glycoprotein and CYP3A4 inhibition. However, the rivaroxaban label recommends against the concomitant use of dronedarone, but not amiodarone, citing a lack of evidence on the concomitant use of rivaroxaban and dronedarone as the reason for the different recommendations. In this report, we discuss evidence from clinical studies and physiologically based pharmacokinetic modelling on the potential for increased rivaroxaban exposure resulting from drug-drug interaction between rivaroxaban and dronedarone or amiodarone. The current evidence supports the same clinical status and concomitant use of either amiodarone or dronedarone with rivaroxaban, which could be considered in future recommendations.

Population Pharmacokinetic Model of Amiodarone and N-Desethylamiodarone Focusing on Glucocorticoid and Inflammation

Some population pharmacokinetic models for amiodarone (AMD) did not incorporate N-desethylamiodarone (DEA) concentration. Glucocorticoids activate CYP3A4 activity, metabolizing AMD. In contrast, CYP3A4 activity may decrease under inflammation conditions. However, direct evidence for the role of glucocorticoid or inflammation on the pharmacokinetics of AMD and DEA is lacking. The pilot study aimed to address this gap using a population pharmacokinetic analysis of AMD and DEA. A retrospective cohort observational study in adult patients who underwent AMD treatment with trough concentration measurement was conducted at Tokyo Women's Medical University, Medical Center East from June 2015 to March 2019. Both structural models of AMD and DEA applied 1-compartment models, which included significant covariates using a stepwise forward selection and backward elimination method. The eligible 81 patients (C-reactive protein level: 0.26 [interquartile range; 0.09-1.92] mg/dL) had a total of 408 trough concentrations for both AMD and DEA. The median trough concentrations were 0.49 [0.31-0.81] µg/mL for AMD and 0.43 [0.28-0.71] µg/mL for DEA during a median follow-up period of 446 [147-1059] d. Three patients received low-dose oral glucocorticoid. The final model identified that AMD clearance was 7.9 L/h, and the apparent DEA clearance was 10.3 L/h. Co-administered glucocorticoids lowered apparent DEA clearance by 35%. These results indicate that co-administered glucocorticoids may increase DEA concentrations in patients without severe inflammation.

Pirfenidone 5-hydroxylation is mainly catalysed by CYP1A2 and partly catalysed by CYP2C19 and CYP2D6 in the human liver

Pirfenidone is a first-line drug for the treatment of idiopathic pulmonary fibrosis. The primary metabolic pathways of pirfenidone in humans are 5-hydroxylation and subsequent oxidation to 5-carboxylpirfenidone. The aims of this study were to determine the cytochrome P450 isoforms responsible for pirfenidone 5-hydroxylation and to evaluate their contributions in human liver microsomes (HLM).Among the recombinant P450 isoforms, CYP1A2, CYP2D6, CYP2C19, CYP2A6, and CYP2B6 were shown to catalyse the 5-hydroxylation of pirfenidone. Pirfenidone 5-hydroxylase activity by HLM was inhibited by α-naphthoflavone (by 45%), 8-methoxypsolaren (by 84%), tranylcypromine (by 53%), and quinidine (by 15%), which are CYP1A2, CYP1A2/CYP2A6/CYP2C19, CYP2A6/CYP2C19, and CYP2D6 inhibitors, respectively.In 17 individual HLM donors, pirfenidone 5-hydroxylase activity was significantly correlated with phenacetin O-deethylase (r = 0.89, P < 0.001) and S-mephenytoin 4'-hydroxylase activities (r = 0.51, P < 0.05), which are CYP1A2 and CYP2C19 marker activities, respectively.By using the relative activity factors, the contributions of CYP1A2, CYP2C19, and CYP2D6 to pirfenidone 5-hydroxylation in the human liver were 72.8%, 11.8%, and 8.9%, respectively.In conclusion, we clearly demonstrated the predominant P450 involved in pirfenidone 5-hydroxylation in the human liver is CYP1A2, with CYP2C19 and CYP2D6 playing a minor role.

Differential Interactions of Selected Phytocannabinoids with Human CYP2D6 Polymorphisms

Cytochrome P450 2D6 (CYP2D6) is primarily expressed in the liver and in the central nervous system. It is known to be highly polymorphic in nature. It metabolizes several endogenous substrates such as anandamide (AEA). Concomitantly, it is involved in phase 1 metabolism of several antidepressants, antipsychotics, and other drugs. Research in the field of phytocannabinoids (pCBs) has recently accelerated owing to their legalization and increasing medicinal use for pain and inflammation. The primary component of cannabis is THC, which is well-known for its psychotropic effects. Since CYP2D6 is an important brain and liver P450 and is known to be inhibited by CBD, we investigated the interactions of four important highly prevalent CYP2D6 polymorphisms with selected phytocannabinoids (CBD, THC, CBDV, THCV, CBN, CBG, CBC, β-carophyllene) that are rapidly gaining popularity. We show that there is differential binding of CYP2D6*17 to pCBs as compared to WT CYP2D6. We also perform a more detailed comparison of WT and *17 CYP2D6, which reveals the possible regulation of AEA metabolism by CBD. Furthermore, we use molecular dynamics to delineate the mechanism of this binding, inhibition, and regulation. Taken together, we have found that the interactions of CYP2D6 with pCBs vary by polymorphism and by specific pCB class.

Keeping a balance in chronic lymphocytic leukemia (CLL) patients taking ibrutinib: ibrutinib-associated adverse events and their management based on drug interactions

INTRODUCTION

Ibrutinib is a highly effective drug for patients with chronic lymphocytic leukemia (CLL), and is well tolerated even by older patients and those unfit to receive conventional immuno-chemotherapy.

AREAS COVERED

The occurrence of adverse events was revealed as a major cause of ibrutinib failure in the real-world. Ibrutinib-induced lymphocytosis carries the risk of an untimely interruption of therapy because it may be misinterpreted as disease progression. In addition, drug interactions can worsen ibrutinib-associated toxicities by increasing the plasma concentration of ibrutinib. In this review, we present a case of major hemorrhage and atrial fibrillation (AF) during ibrutinib use and summarize the adverse events associated with ibrutinib. Furthermore, the practical management of ibrutinib-associated toxicities was covered with reference to a drug interaction mechanism.

EXPERT OPINION

Clinicians should examine the prescribed drugs prior to ibrutinib initiation and carefully monitor toxicities while taking ibrutinib. A reduced dose of ibrutinib with the concurrent use of CYP3A inhibitors such as antifungal agents could be an attractive strategy to reduce toxicities and may confer financial benefits. Reducing unexpected toxicities is as significant as achieving treatment response in the era of life-long therapy with ibrutinib in patients with CLL.

Do Inhibitory Metabolites Impact DDI Risk Assessment? Analysis of in vitro and in vivo Data from NDA Reviews Between 2013 and 2018

Evaluating the potential of new drugs and their metabolites to cause drug-drug interactions (DDIs) is critical for understanding drug safety and efficacy. Although multiple analyses of proprietary metabolite testing data have been published, no systematic analyses of metabolite data collected according to current testing criteria have been conducted. To address this knowledge gap, 120 new molecular entities approved between 2013 and 2018 were reviewed. Comprehensive data on metabolite-to-parent area under the curve ratios (AUC_M /AUC_P ), inhibitory potency of parent and metabolites, and clinical DDIs were collected. Sixty-four percent of the metabolites quantified in vivo had AUC_M /AUC_P  ≥ 0.25 and 75% of these metabolites were tested for cytochrome P450 (CYP) inhibition in vitro, resulting in 15 metabolites with potential DDI risk identification. Although 50% of the metabolites with AUC_M /AUC_P  < 0.25 were also tested in vitro, none of them showed meaningful CYP inhibition potential. The metabolite percentage of plasma total radioactivity cutoff of ≥ 10% did not appear to add value to metabolite testing strategies. No relationship between metabolite versus parent drug polarity and inhibition potency was observed. Comparison of metabolite and parent maximum concentration (C_max ) divided by inhibition constant (K_i ) values suggested that metabolites can contribute to in vivo DDIs and, hence, quantitative prediction of clinical DDI magnitude may require both parent and metabolite data. This systematic analysis of metabolite data for newly approved drugs supports an AUC_M /AUC_P cutoff of ≥ 0.25 to warrant metabolite in vitro CYP screening to adequately characterize metabolite inhibitory DDI potential and support quantitative DDI predictions.

Structure-based virtual screening of CYP1A1 inhibitors: towards rapid tier-one assessment of potential developmental toxicants

Cytochrome P450 1A1 (CYP1A1) metabolizes estrogens, melatonin, and other key endogenous signaling molecules critical for embryonic/fetal development. The enzyme has increasing expression during pregnancy, and its inhibition or knockout increases embryonic/fetal lethality and/or developmental problems. Here, we present a virtual screening model for CYP1A1 inhibitors based on the orthosteric and predicted allosteric sites of the enzyme. Using 1001 reference compounds with CYP1A1 activity data, we optimized the decision thresholds of our model and classified the training compounds with 68.3% balanced accuracy (91.0% sensitivity and 45.7% specificity). We applied our final model to 11 known CYP1A1 orthosteric binders and related compounds, and found that our ranking of the known orthosteric binders generally agrees with the relative activity of CYP1A1 in metabolizing these compounds. We also applied the model to 22 new test compounds with unknown/unclear CYP1A1 inhibitory activity, and predicted 16 of them are CYP1A1 inhibitors. The CYP1A1 potency and modes of inhibition of these 22 compounds were experimentally determined. We confirmed that most predicted inhibitors, including drugs contraindicated during pregnancy (amiodarone, bicalutamide, cyproterone acetate, ketoconazole, and tamoxifen) and environmental agents suspected to be endocrine disruptors (bisphenol A, diethyl and dibutyl phthalates, and zearalenone), are indeed potent inhibitors of CYP1A1. Our results suggest that virtual screening may be used as a rapid tier-one method to screen for potential CYP1A1 inhibitors, and flag them out for further experimental evaluations.

Exploration of inhibition potential of isoniazid and its metabolites towards CYP2E1 in human liver microsomes through LC-MS/MS analysis

Isoniazid (INH) is the first-line anti-tubercular drug that is used both for the prophylaxis as well as the treatment of tuberculosis (TB). The patients with TB are more vulnerable to secondary infections and other health complications, hence, they are usually administered a cocktail of drugs. This increases the likelihood of drug-drug interactions (DDIs). INH is clinically proven to interact with drugs like phenytoin, carbamazepine, diazepam, triazolam, acetaminophen, etc. Most of such clinical observations have been supported by in vitro inhibition studies involving INH and cytochrome P450 (CYP) enzymes. A few published in vitro studies have explored the CYP2E1 inhibition potential of INH to explain its interactions with acetaminophen and other CY2E1 substrates, such as chlorzoxazone, but none of them were able to demonstrate any significant inhibition of the enzyme by the drug. It was reported that metabolites of INH, such as acetylhydrazine and hydrazine, were bioactivated by CYP2E1, highlighting that perhaps the drug metabolites were responsible for the mechanism based inhibition (MBI) of the enzyme. Therefore, the purpose of this investigation was to explore CYP2E1 enzyme inhibition potential of INH and its four major metabolites, viz., acetylisoniazid, isonicotinic acid, acetylhydrazine and hydrazine, using human liver microsomes (HLM). Additionally, we determined the fraction unbound in microsomal incubation (fu_mic) for all the five compounds using equilibrium dialysis assay. We observed that INH and its metabolites had lower propensity for microsomal binding, and the metabolites also lacked the potential to inhibit CYP2E1 enzyme, either by direct inhibition or through MBI. This suggests involvement of some other mechanism to explain interactions of INH with CY2E1 substrates, signifying need of further exploration.

Factors affecting serum phenobarbital concentration changes in pediatric patients receiving elixir and powder formulations

Background

Phenobarbital (PB) is commonly used as elixir and powder formulations in pediatric care. Its dose adjustment is performed based on individual drug concentration monitoring. Few studies have comprehensively analyzed the variation factors for serum PB concentration. In this study, we retrospectively investigated the factors that influence serum PB concentration and assessed the impacts of dosage formulation and administration route.

Methods

This retrospective cohort study covered clinical data from January 2007 to September 2019 at Mie University Hospital. The present study included 60 pediatric patients administered the elixir and powder of PB through oral route and enteral tube. Simple and multiple linear regression analyses were performed to identify the risk factors that affect the weight-corrected PB serum concentration/dose (C/D) ratio in pediatric patients. Six subgroups were also established according to the concomitant use of drugs that potentially inhibit PB metabolism, dosage formulation, and administration route to investigate the difference in the PB C/D ratio among the subgroups.

Results

A significant regression equation to predict the PB C/D ratio was found through simple and multiple linear regression analyses, with an adjusted coefficient of determination of 0.53 (p < 0.001). Further, the concomitant uses of valproic acid (VPA) or amiodarone, which were the only two drugs seen in this study as potential inhibitors of PB, was found to have the greatest effect on the PB C/D ratio (standardized partial regression coefficient (β) = 0.543, p < 0.001). Furthermore, a significant difference in the PB C/D ratio was found between the subgroups classified by the concomitant use of VPA or amiodarone (p = 0.002). However, there were no significant correlations between the PB C/D ratio, dosage formulation, and administration route.

Conclusions

The most influential factor on the PB C/D ratio was the concomitant use of VPA or amiodarone with PB. This result could provide an important perspective in pediatric drug therapy where elixir and powder formulations are administered via the oral route and enteral tube.

Amiodarone Enhances Anticonvulsive Effect of Oxcarbazepine and Pregabalin in the Mouse Maximal Electroshock Model

Accumulating experimental studies show that antiarrhythmic and antiepileptic drugs share some molecular mechanisms of action and can interact with each other. In this study, the influence of amiodarone (a class III antiarrhythmic drug) on the antiseizure action of four second-generation antiepileptic drugs was evaluated in the maximal electroshock model in mice. Amiodarone, although ineffective in the electroconvulsive threshold test, significantly potentiated the antielectroshock activity of oxcarbazepine and pregabalin. Amiodarone, given alone or in combination with oxcarbazepine, lamotrigine, or topiramate, significantly disturbed long-term memory in the passive-avoidance task in mice. Brain concentrations of antiepileptic drugs were not affected by amiodarone. However, the brain concentration of amiodarone was significantly elevated by oxcarbazepine, topiramate, and pregabalin. Additionally, oxcarbazepine and pregabalin elevated the brain concentration of desethylamiodarone, the main metabolite of amiodarone. In conclusion, potentially beneficial action of amiodarone in epilepsy patients seems to be limited by neurotoxic effects of amiodarone. Although results of this study should still be confirmed in chronic protocols of treatment, special precautions are recommended in clinical conditions. Coadministration of amiodarone, even at low therapeutic doses, with antiepileptic drugs should be carefully monitored to exclude undesired effects related to accumulation of the antiarrhythmic drug and its main metabolite, desethylamiodarone.

The Role of Structure and Biophysical Properties in the Pleiotropic Effects of Statins

Statins are a class of drugs used to lower low-density lipoprotein cholesterol and are amongst the most prescribed medications worldwide. Most statins work as a competitive inhibitor of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGR), but statin intolerance from pleiotropic effects have been proposed to arise from non-specific binding due to poor enzyme-ligand sensitivity. Yet, research into the physicochemical properties of statins, and their interactions with off-target sites, has not progressed much over the past few decades. Here, we present a concise perspective on the role of statins in lowering serum cholesterol levels, and how their reported interactions with phospholipid membranes offer a crucial insight into the mechanism of some of the more commonly observed pleiotropic effects of statin administration. Lipophilicity, which governs hepatoselectivity, is directly related to the molecular structure of statins, which dictates interaction with and transport through membranes. The structure of statins is therefore a clinically important consideration in the treatment of hypercholesterolaemia. This review integrates the recent biophysical studies of statins with the literature on the physiological effects and provides new insights into the mechanistic cause of statin pleiotropy, and prospective means of understanding the cholesterol-independent effects of statins.

Drug interactions and pharmacogenetic factors contribute to variation in apixaban concentration in atrial fibrillation patients in routine care

Factor Xa-inhibitor apixaban is an oral anticoagulant prescribed in atrial fibrillation (AF) for stroke prevention. Its pharmacokinetic profile is known to be affected by cytochrome P450 (CYP)3A metabolism, while it is also a substrate of the efflux transporters ATP-binding cassette (ABC)B1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein, BCRP). In this study, we assessed the impact of interacting medication and pharmacogenetic variation to better explain apixaban concentration differences among 358 Caucasian AF patients. Genotyping (ABCG2, ABCB1, CYP3A4*22, CYP3A5*3) was performed by TaqMan assays, and apixaban quantified by mass spectrometry. The typical patient was on average 77.2 years old, 85.5 kg, and had a serum creatinine of 103.1 µmol/L. Concomitant amiodarone, an antiarrhythmic agent and moderate CYP3A/ABCB1 inhibitor, the impaired-function variant ABCG2 c.421C > A, and sex predicted higher apixaban concentrations when controlling for age, weight and serum creatinine (multivariate regression; R² = 0.34). Our findings suggest that amiodarone and ABCG2 genotype contribute to interpatient apixaban variability beyond known clinical factors.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

Alginate-based drug oral targeting using bio-micro/nano encapsulation technologies

INTRODUCTION

Oral delivery is the most common administrated drug delivery path. However, oral administration of lipophilic drugs has some limitations: they have poor dose-response due to low and varied dissolution kinetics and oral bioavailability with sub-optimal dissolution within the aqueous gastrointestinal microenvironment. Therefore, there is a need for robust formulating methods that protect the drug until it reaches to its optimum absorption site, allowing its optimum pharmacological effects via increasing its intestinal permeation and bioavailability.

AREA COVERED

Herein, we provide insights on orally administered lipophilic drug delivery systems. The detailed description of the obstacles associated with the oral bioavailability of lipophilic drugs are also discussed. Following this, techniques to overcome these obstacles with much emphasis on optimal safety and efficacy are addressed. Newly designed ionic vibrational jet flow encapsulation technology has enormous growth in lipophilic drug delivery systems, which is discussed thereafter.

EXPERT OPINION

Researchers have shown interest in drug's encapsulation. A combination of drug-bile acid and microencapsulation methods can be one promising strategy to improve the oral delivery of lipophilic drugs. However, the most critical aspect of this approach is the selection of bile acids, polymer, and encapsulation technology.

Cardiovascular adverse events associated with hydroxychloroquine and chloroquine: A comprehensive pharmacovigilance analysis of pre-COVID-19 reports

AIM

There is a clinical need for safety data regarding hydroxychloroquine (HCQ) and chloroquine (CQ) during the coronavirus (COVID-19) pandemic. We analysed real-world data using the U.S. Food and Drug Administration Adverse Events Reporting System (FAERS) database to assess HCQ/CQ-associated cardiovascular adverse events (CVAEs) in pre-COVID-19 reports.

METHODS

We conducted disproportionality analysis of HCQ/CQ in the FAERS database (07/2014-9/2019), using reporting odds ratio (ROR) and the lower bound of the information component 95% credibility interval (IC₀₂₅ ).

RESULTS

The full database contained 6 677 225 reports with a mean (±SD) age of 53 (±17) years and 74% females. We identified 4895 reports of HCQ/CQ related adverse events, of which 696 (14.2%) were CVAEs. Compared with the full database, HCQ/CQ use was associated with a higher reporting rate of major CVAEs, including cardiomyopathy (n = 86 [1.8%], ROR = 29.0 [23.3-35.9]), QT prolongation (n = 43 [0.9%], ROR = 4.5 [3.3-6.1]), cardiac arrhythmias (n = 117 [2.4%], ROR = 2.2 [1.8-2.7]) and heart failure (n = 136 [2.8%], ROR = 2.2 [1.9-2.7], all IC₀₂₅ > 0). No statistically significant differences were observed between sex and age groups. CVAEs were reported more often in patients with systemic lupus erythematosus and Sjogren's syndrome. HCQ/CQ-associated CVAEs demonstrated subsequent hospitalization and mortality rates of 39% and 8%, respectively. Overdose reports demonstrated an increased frequency of QT prolongation and ventricular arrhythmias (35% and 25%, respectively).

CONCLUSION

In a real-world setting, HCQ/CQ treatment is associated with higher reporting rates of various CVAEs, particularly cardiomyopathy, QT prolongation, cardiac arrhythmias and heart failure. HCQ/CQ-associated CVAEs result in high rates of severe outcomes and should be carefully considered as an off-label indication, especially for patients with cardiac disorders.

Risk of severe hypoglycemic events from amiodarone-sulfonylureas interactions: A population-based nested case-control study

PURPOSE

To evaluate whether concomitant use of amiodarone and sulfonylureas is associated with an increased risk of serious hypoglycemia.

METHODS

We conducted two nested case-control studies by analyzing the Taiwan National Health Insurance Research Database from 2008 to 2013 among diabetic patients continuously receiving sulfonylureas. Cases were defined as patients with severe hypoglycemia and those with a composite outcome of severe hypoglycemia, altered consciousness, and fall-related fracture in the first and second study, respectively. In both studies, each case was individually matched up to 10 randomly-selected controls. Conditional logistic regressions were employed to estimate odds ratios (ORs).

RESULTS

We identified 1343 cases and 11 597 controls as well as 2848 cases of composite events and 24 808 controls among 46 317 sulfonylurea users. Concurrent use of amiodarone with sulfonylureas was associated with a 1.56-fold (95% CI: 0.98-2.46) increased risk of severe hypoglycemia, despite not statistically significant. Notably, an approximately 2-fold increased risk of severe hypoglycemia was observed with amiodarone therapy lasting for >180 days (adjusted OR: 2.08; 95% CI: 1.01-4.30) or at a daily dose greater than 1 defined daily dose (adjusted OR: 2.21; 95% CI: 1.25-3.91) when concurrently administrating sulfonylureas. A significantly increased risk of hypoglycemia-related composite events was also found with amiodarone concurrently used with sulfonylureas (adjusted OR: 1.59; 95% CI: 1.13-2.24).

CONCLUSIONS

Concurrent use of amiodarone and sulfonylureas is associated with an increased risk of serious hypoglycemia among diabetic patients, with an elevated risk for amiodarone used in a long-term or at a high daily dose.

CYP2C19 and CYP3A4 activity and ADP-induced platelet reactivity in prasugrel- or ticagrelor-treated STEMI patients: monocentric study in PRAGUE-18 trial participants

We assessed the contribution of CYP2C19 and CYP3A4 metabolic activity to the ADP-induced platelet aggregation 1h and 24h after a loading dose of 60 mg prasugrel or 180 mg ticagrelor in patients with ST-elevation myocardial infarction (STEMI). Further, we assessed the contribution of CYP2C19 polymorphisms and medication to the CYP enzymatic activity.Patients with STEMI were randomly assigned to the treatment with prasugrel (n = 51) or ticagrelor (n = 46). Metabolic activity of CYP2C19 and CYP3A4 was assessed by the rate of 5-hydroxylation and sulfoxidation of lansoprazole. Further, patients were genotyped for CYP2C19 *2 and *17 alleles.In prasugrel-treated patients, high ADP-induced platelet reactivity 1h after the loading dose positively correlated with 5OH-lansoprazole/lansoprazole ratio (r = 0.44, p = 0.002), a marker of CYP2C19 metabolic activity, and negatively with lansoprazole-sulfone/lansoprazole ratio, which reflects CYP3A4 metabolic activity (r = -0.35, p = 0.018).CYP2C19 poor metabolizers had lower 5OH-lansoprazole/lansoprazole ratio and higher lansoprazole-sulfone/lansoprazole ratio, but without any effect on the ADP-induced platelet reactivity. The treatment with amiodarone, a CYP3A4 inhibitor, influenced neither the metabolic ratios nor the ADP-induced platelet reactivity.The CYP3A4 and CYP2C19 metabolic activity is associated with ADP-induced platelet reactivity in prasugrel-treated, but not ticagrelor-treated patients with STEMI.

Time-dependent enzyme inactivation: Numerical analyses of in vitro data and prediction of drug-drug interactions

Cytochrome P450 (CYP) enzyme kinetics often do not conform to Michaelis-Menten assumptions, and time-dependent inactivation (TDI) of CYPs displays complexities such as multiple substrate binding, partial inactivation, quasi-irreversible inactivation, and sequential metabolism. Additionally, in vitro experimental issues such as lipid partitioning, enzyme concentrations, and inactivator depletion can further complicate the parameterization of in vitro TDI. The traditional replot method used to analyze in vitro TDI datasets is unable to handle complexities in CYP kinetics, and numerical approaches using ordinary differential equations of the kinetic schemes offer several advantages. Improvement in the parameterization of CYP in vitro kinetics has the potential to improve prediction of clinical drug-drug interactions (DDIs). This manuscript discusses various complexities in TDI kinetics of CYPs, and numerical approaches to model these complexities. The extrapolation of CYP in vitro TDI parameters to predict in vivo DDIs with static and dynamic modeling is discussed, along with a discussion on current gaps in knowledge and future directions to improve the prediction of DDI with in vitro data for CYP catalyzed drug metabolism.

Association between clinically relevant toxicities of pazopanib and sunitinib and the use of weak CYP3A4 and P-gp inhibitors

PURPOSE

Sunitinib and pazopanib, two tyrosine kinase inhibitors (TKI), may be targets of potential pharmacokinetic drug-drug interactions (P-PK-DDIs). While strong cytochrome P4503A (CYP3A4) inhibitors or inducers should cause a clinically relevant modification in plasma TKI concentrations, the effect of weak inhibitors is unknown. The objective of this study was to evaluate the association between weak P-PK-DDI and clinically relevant toxicity in real life.

PATIENTS AND METHODS

This was a single-center retrospective study including patients treated with sunitinib or pazopanib for any malignancies, for whom a PK-DDI analysis was performed before starting TKI. The primary endpoint was the correlation between P-PK-DDIs and a dose decrease after 1 month of treatment. The secondary endpoint was the correlation between PK-DDIs and drug withdrawal due to toxicity.

RESULTS

Seventy-six patients were assessed. A P-PK-DDI with weak CYP3A4 or P-gp inhibition was found in 14 patients. In patients with P-PK-DDI or without, the dose was reduced during the first month in 57.1% and 17.7% (p = 0.003) and the drug withdrawn in 42.8% and 11.3% (p = 0.011), respectively. In multivariate analysis, a significant correlation was found between P-PK-DDI (CYP3A4 and P-gp inhibitors) and dose reduction, and between drug withdrawal and PK-DDI (CYP3A4 inhibitors).

CONCLUSION

P-PK-DDI was correlated with dose reduction and drug withdrawal due to toxicity. The causality of this relationship warrants to be assessed; therefore, therapeutic drug monitoring is necessary in patients treated with TKI.

Drug-Drug Interactions Of Amiodarone And Quinidine On The Pharmacokinetics Of Eliglustat In Rats

Background

Eliglustat, a new oral substrate-reduction therapy, was recently approved as a first-line therapy for Gaucher's disease type 1 (GD1) patients.

Purpose

The purpose of the present study was to develop and validate a simple UPLC-MS/MS method for the measurement of plasma-eliglustat concentration and to investigate the effects of amiodarone and quinidine on eliglustat metabolism in rats.

Methods

Eighteen rats were randomly divided into three groups (n=6): control (0.5% CMC-Na, group A), amiodarone (60 mg/kg, group B), and quinidine (100 mg/kg, group C). Thirty minutes later, 10 mg/kg eliglustat was orally administered to each rat and concentrations of eliglustat in the rats determined by our UPLC-MS/MS method.

Results

Amiodarone and quinidine increased the main pharmacokinetic parameters (AUC0→_t, AUC_0→∞, and C_max) of eliglustat significantly and decreased clearance obviously.

Conclusion

Amiodarone and quinidine can elevate eliglustat exposure and have an inhibitory effect on eliglustat metabolism. Clearly, appropriate pharmacological studies of eliglustat in patients treated with amiodarone or quinidine should be done in future.

Inhibition of Hepatic CYP2D6 by the Active N-Oxide Metabolite of Sorafenib

The multikinase inhibitor sorafenib (SOR) is used to treat patients with hepatocellular and renal carcinomas. SOR undergoes CYP-mediated biotransformation to a pharmacologically active N-oxide metabolite (SNO) that has been shown to accumulate to varying extents in individuals. Kinase inhibitors like SOR are frequently coadministered with a range of other drugs to improve the efficacy of anticancer drug therapy and to treat comorbidities. Recent evidence has suggested that SNO is more effective than SOR as an inhibitor of CYP3A4-mediated midazolam 1'-hydroxylation. CYP2D6 is also reportedly inhibited by SOR. The present study assessed the possibility that SNO might contribute to CYP2D6 inhibition. The inhibition kinetics of CYP2D6-mediated dextromethorphan O-demethylation were analyzed in human hepatic microsomes, with SNO found to be ~ 19-fold more active than SOR (K_is 1.8 ± 0.3 μM and 34 ± 11 μM, respectively). Molecular docking studies of SOR and SNO were undertaken using multiple crystal structures of CYP2D6. Both molecules mediated interactions with key amino acid residues in putative substrate recognition sites of CYP2D6. However, a larger number of H-bonding interactions was noted between the N-oxide moiety of SNO and active site residues that account for its greater inhibition potency. These findings suggest that SNO has the potential to contribute to pharmacokinetic interactions involving SOR, perhaps in those individuals in whom SNO accumulates.

Molecular Dynamics Simulation Framework to Probe the Binding Hypothesis of CYP3A4 Inhibitors

The Cytochrome P450 family of heme-containing proteins plays a major role in catalyzing phase I metabolic reactions, and the CYP3A4 subtype is responsible for the metabolism of many currently marketed drugs. Additionally, CYP3A4 has an inherent affinity for a broad spectrum of structurally diverse chemical entities, often leading to drug-drug interactions mediated by the inhibition or induction of the metabolic enzyme. The current study explores the binding of selected highly efficient CYP3A4 inhibitors by docking and molecular dynamics (MD) simulation protocols and their binding free energy calculated using the WaterSwap method. The results indicate the importance of binding pocket residues including Phe57, Arg105, Arg106, Ser119, Arg212, Phe213, Thr309, Ser312, Ala370, Arg372, Glu374, Gly481 and Leu483 for interaction with CYP3A4 inhibitors. The residue-wise decomposition of the binding free energy from the WaterSwap method revealed the importance of binding site residues Arg106 and Arg372 in the stabilization of all the selected CYP3A4-inhibitor complexes. The WaterSwap binding energies were further complemented with the MM(GB/PB)SA results and it was observed that the binding energies calculated by both methods do not differ significantly. Overall, our results could guide towards the use of multiple computational approaches to achieve a better understanding of CYP3A4 inhibition, subsequently leading to the design of highly specific and efficient new chemical entities with suitable ADMETox properties and reduced side effects.

Amiodarone and thyroid physiology, pathophysiology, diagnosis and management

Although amiodarone is considered the most effective antiarrhythmic agent, its use is limited by a wide variety of potential toxicities. The purpose of this review is to provide a comprehensive "bench to bedside" overview of the ways amiodarone influences thyroid function. We performed a systematic search of MEDLINE to identify peer-reviewed clinical trials, randomized controlled trials, meta-analyses, and other clinically relevant studies. The search was limited to English-language reports published between 1950 and 2017. Amiodarone was searched using the terms adverse effects, hypothyroidism, myxedema, hyperthyroidism, thyroid storm, atrial fibrillation, ventricular arrhythmia, and electrical storm. Google and Google scholar as well as bibliographies of identified articles were reviewed for additional references. We included 163 germane references in this review. Because amiodarone is one of the most frequently prescribed antiarrhythmic drugs in the United States, the mechanistic, diagnostic and therapeutic information provided is relevant for practicing clinicians in a wide range of medical specialties.

Influence of concomitant medication on plasma concentration of amiodarone in patients with atrial fibrillation - a pilot study

Background

Although amiodarone is a drug with many side effects, it is one of the most commonly used drugs in the treatment and prophylaxis of supraventricular and ventricular arrhythmias.

Aim

The purpose of this pilot study was to evaluate plasma concentrations of amiodarone in patients with atrial fibrillation (AF) and to identify possible drug-drug interactions between amiodarone and concomitant medications.

Method

A prospective observational study was conducted in 27 consecutive patients treated with amiodarone from May to July 2017 in a Clinical University Hospital. The patients included met our inclusion criteria. HPLC-UV was the device used to determine the plasma concentration of amiodarone.

Results

Only 51.8% of the patients had amiodarone plasma concentration within therapeutic interval (500–2500 ng/ml). The drugs associated to amiodarone in the therapeutic plan were diuretics, beta blockers, statins, antiplatelets, fluoroquinolones, non-steroidal anti-inflammatory drugs. We observed a statistically significant difference between the plasmatic concentrations of amiodarone in patients treated with furosemide vs. patients concomitantly treated with other drugs. Interactions between other mentioned drugs and amiodarone were not registered. We can report an underuse of amiodarone for more than 50% of the patients. Also, we found a significant interaction between furosemide and amiodarone, most likely through the interaction with MDR.

Conclusion

Furosemide may influence the pharmacokinetics of P-gp-interfering drugs. However, the relevance of these findings needs to be confirmed and further research is needed to characterize the interaction between amiodarone and furosemide.

Importance of in vitro conditions for modeling the in vivo dose in humans by in vitro-in vivo extrapolation (IVIVE)

In vitro studies are increasingly proposed to replace in vivo toxicity testing of substances. We set out to apply physiologically based pharmacokinetic (PBPK) modeling to predict the in vivo dose of amiodarone that leads to the same concentration-time profile in the supernatant and the cell lysate of cultured primary human hepatic cells (PHH). A PBPK human model was constructed based on the structure and tissue distribution of amiodarone in a rat model and using physiological human parameters. The predicted concentration-time profile in plasma was in agreement with human experimental data with the unbound fraction of amiodarone in plasma crucially affecting the goodness-of-fit. Using the validated kinetic model, we subsequently described the in vitro concentration-time data of amiodarone in PHH culture. However, this could be only appropriately modeled under conditions of zero protein binding and the very low clearance of the in vitro system in PHH culture. However, these represent unphysiological conditions and, thus, the main difference between the in vivo and the in vitro systems. Our results reveal that, for meaningful quantitative extrapolation from in vitro to in vivo conditions in PBPK studies, it is essential to avoid non-intended differences between these conditions. Specifically, clearance and protein binding, as demonstrated in our analysis of amiodarone modeling, are important parameters to consider.

Rosuvastatin-Induced Rhabdomyolysis - Possible Role of Ticagrelor and Patients' Pharmacogenetic Profile

Up to the beginning of 2018, a total of eight cases describing rare but clinically important drug interactions between rosuvastatin and ticagrelor which resulted in rhabdomyolysis have been noted in the Global World Health Organization (WHO) adverse drug reaction (ADR) database (VigiBase) as well as in available literature. There are several possible factors which could contribute to the onset of rhabdomyolysis: old age, initially excessive rosuvastatin dose, drug-drug interactions (DDI) on metabolic enzymes (CYPs and UGTs) and drug transporter levels (ABCB1, ABCG2, OATP1B1) and pharmacogenetic predisposition. We reviewed all available cases plus the case of an 87-year-old female Croatian/Caucasian patient who developed rhabdomyolysis following concomitant treatment with rosuvastatin and ticagrelor. The results of the pharmacogenetic analysis indicated that the patient was a carrier of inactivating alleles CYP2C9*1/*3, CYP3A4*1/*22, CYP3A5*3/*3, CYP2D6*1/*4, UGT1A1*28/*28, UGT2B7 -161C/T, ABCB1 3435C/T and ABCB1 1237C/T which could have added to the interactions not only between ticagrelor and rosuvastatin but also other concomitantly prescribed medicines, such as amiodarone and proton pump inhibitors. In this case report, the possible multifactorial causes for rhabdomyolysis following concomitant use of rosuvastatin and ticagrelor such as old age, polypharmacy, renal impairment, along with pharmacogenetics will be discussed.

Effect of Toxicants on Fatty Acid Metabolism in HepG2 Cells

Impairment of hepatic fatty acid metabolism can lead to liver steatosis and injury. Testing drugs for interference with hepatic fatty acid metabolism is therefore important. To find out whether HepG2 cells are suitable for this purpose, we investigated the effect of three established fatty acid metabolism inhibitors and of three test compounds on triglyceride accumulation, palmitate metabolism, the acylcarnitine pool and dicarboxylic acid accumulation in the cell supernatant and on ApoB-100 excretion in HepG2 cells. The three established inhibitors [etomoxir, methylenecyclopropylacetic acid (MCPA), and 4-bromocrotonic acid (4-BCA)] depleted mitochondrial ATP at lower concentrations than cytotoxicity occurred, suggesting mitochondrial toxicity. They inhibited palmitate metabolism at similar or lower concentrations than ATP depletion, and 4-BCA was associated with cellular fat accumulation. They caused specific changes in the acylcarnitine pattern and etomoxir an increase of thapsic (C18 dicarboxylic) acid in the cell supernatant, and did not interfere with ApoB-100 excretion (marker of VLDL export). The three test compounds (amiodarone, tamoxifen, and the cannabinoid WIN 55,212-2) depleted the cellular ATP content at lower concentrations than cytotoxicity occurred. They all caused cellular fat accumulation and inhibited palmitate metabolism at similar or higher concentrations than ATP depletion. They suppressed medium-chain acylcarnitines in the cell supernatant and amiodarone and tamoxifen impaired thapsic acid production. Tamoxifen and WIN 55,212-2 decreased cellular ApoB-100 excretion. In conclusion, the established inhibitors of fatty acid metabolism caused the expected effects in HepG2 cells. HepG cells proved to be useful for the detection of drug-associated toxicities on hepatocellular fatty acid metabolism.

In Vitro Drug-Drug Interaction Potential of Sulfoxide and/or Sulfone Metabolites of Albendazole, Triclabendazole , Aldicarb, Methiocarb, Montelukast and Ziprasidone

BACKGROUND

The use of polypharmacy in the present day clinical therapy has made the identification of clinical drug-drug interaction risk an important aspect of drug development process. Although many drugs can be metabolized to sulfoxide and/or sulfone metabolites, seldom is known on the CYP inhibition potential and/or the metabolic fate for such metabolites.

OBJECTIVE

The key objectives were: a) to evaluate the in vitro CYP inhibition potential of selected parent drugs with sulfoxide/sulfone metabolites; b) to assess the in vitro metabolic fate of the same panel of parent drugs and metabolites.

METHODS

In vitro drug-drug interaction potential of test compounds was investigated in two stages; 1) assessment of CYP450 inhibition potential of test compounds using human liver microsomes (HLM); and 2) assessment of test compounds as substrate of Phase I enzymes; including CYP450, FMO, AO and MAO using HLM, recombinant human CYP enzymes (rhCYP), Human Liver Cytosol (HLC) and Human Liver Mitochondrial (HLMit). All samples were analysed by LC-MS-MS method.

RESULTS

CYP1A2 was inhibited by methiocarb, triclabendazole, triclabendazole sulfoxide, and ziprasidone sulfone with IC50 of 0.71 µM, 1.07 µM, 4.19 µM, and 17.14 µM, respectively. CYP2C8 was inhibited by montelukast, montelukast sulfoxide, montelukast sulfone, tribendazole, triclabendazole sulfoxide, and triclabendazole sulfone with IC50 of 0.08 µM, 0.05 µM, 0.02 µM, 3.31 µM, 8.95 µM, and 1.05 µM, respectively. CYP2C9 was inhibited by triclabendazole, triclabendazole sulfoxide, triclabendazole sulfone, montelukast, montelukast sulfoxide and montelukast sulfone with IC50 of 1.17 µM, 1.95 µM, 0.69 µM, 1.34 µM, 3.61 µM and 2.15 µM, respectively. CYP2C19 was inhibited by triclabendazole and triclabendazole sulfoxide with IC50 of 0.25 and 0.22, respectively. CYP3A4 was inhibited by montelukast sulfoxide and triclabendazole with IC50 of 9.33 and 15.11, respectively. Amongst the studied sulfoxide/sulfone substrates, the propensity of involvement of CY2C9 and CYP3A4 enzyme was high (approximately 56% of total) in the metabolic fate experiments.

CONCLUSION

Based on the findings, a proper risk assessment strategy needs to be factored (i.e., perpetrator and/or victim drug) to overcome any imminent risk of potential clinical drug-drug interaction when sulfoxide/sulfone metabolite(s) generating drugs are coadministered in therapy.

Effect of dronedarone on the pharmacokinetics of carvedilol following oral administration to rats

Dronedarone is a CYP2D6 inhibitor; therefore, it is prudent to exercise caution when concurrently administering CYP2D6-metabolized β-blockers because of a lack of published data on potential drug interactions. The aim of this study was to investigate the effect of dronedarone on the pharmacokinetics of orally administered carvedilol in rats. Twenty male Sprague-Dawley rats were randomly divided into two groups and 10mg/kg carvedilol was administered to the rat with or without dronedarone pretreatment in a parallel design. Blood samples were collected before and after 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, and 24h of drug administration. The plasma concentration of carvedilol was determined using LC-MS/MS. The systemic exposure to carvedilol was significantly increased and elimination of carvedilol was significantly decreased in the dronedarone-pretreated rats than in the vehicle-pretreated rats. The one-compartment model with first-order absorption and elimination was sufficient to explain the pharmacokinetic characters after single oral administration of carvedilol to both vehicle-pretreated and dronedarone-pretreated rats. This study suggests that dronedarone inhibits CYP2D6-mediated carvedilol metabolism, and dose adjustment is needed in carvedilol and dronedarone combination therapy. Further studies are needed to clarify the effect of dronedarone on carvedilol and CYP2D6 substrates in clinical use.

Ibrutinib Treatment of Mantle Cell Lymphoma Relapsing at Central Nervous System: A Case Report and Literature Review

Mantle cell lymphoma (MCL) accounts for about 5% of all lymphomas. Its clinical and histological features are heterogeneous. After a frequently good initial response, the disease generally and repeatedly relapses and finally the outcome is poor. Particularly severe is the prognosis of the rare occurrence of CNSi (Central Nervous System involvement). Ibrutinib, an oral inhibitor of Bruton tyrosine kinase (BTK), has shown strong activity in relapsing patients with Chronic Lymphocytic Leukemia (CLL) and MCL. Few reports are available about treatment with ibrutinib of patients presenting CNSi by lymphoproliferative diseases (LPD). In all of them, ibrutinib, at the dosage between 420 and 560 mg/day, showed an impressive effectiveness. Here we describe a case of MCL with CNS relapse showing an excellent response to ibrutinib administered at the unusual dose of 280 mg/day because of concomitant treatment of cardiological disease.

Cardiac voltage-gated ion channels in safety pharmacology: Review of the landscape leading to the CiPA initiative

Voltage gated ion channels are central in defining the fundamental properties of the ventricular cardiac action potential (AP), and are also involved in the development of drug-induced arrhythmias. Many drugs can inhibit cardiac ion currents, including the Na⁺ current (I_Na), L-type Ca²⁺ current (Ica-L), and K⁺ currents (I_to, I_K1, I_Ks, and I_Kr), and thereby affect AP properties in a manner that can trigger or sustain cardiac arrhythmias. Since publication of ICH E14 and S7B over a decade ago, there has been a focus on drug effects on QT prolongation clinically, and on the rapidly activating delayed rectifier current (I_Kr), nonclinically, for evaluation of proarrhythmic risk. This focus on QT interval prolongation and a single ionic current likely impacted negatively some drugs that lack proarrhythmic liability in humans. To rectify this issue, the Comprehensive in vitro proarrhythmia assay (CiPA) initiative has been proposed to integrate drug effects on multiple cardiac ionic currents with in silico modelling of human ventricular action potentials, and in vitro data obtained from human stem cell-derived ventricular cardiomyocytes to estimate proarrhythmic risk of new drugs with improved accuracy. In this review, we present the physiological functions and the molecular basis of major cardiac ion channels that contribute to the ventricle AP, and discuss the CiPA paradigm in drug development.

Dasatinib and Prednisolone Induction Therapy for a Case of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia with Dilated Cardiomyopathy Accompanied by Life-Threatening Ventricular Tachycardia

A 56-year-old man being treated for dilated cardiomyopathy presented with epigastralgia. He was diagnosed with ventricular tachycardia and Philadelphia chromosome-positive acute lymphoblastic leukemia. After treating incessant ventricular tachycardia, we commenced induction therapy for leukemia with dasatinib and prednisolone to minimize toxicity towards cardiomyocytes and the cardiac conduction system. Although dasatinib was temporarily withheld because of a recurrence of ventricular tachycardia, we rechallenged dasatinib while using bisoprolol and amiodarone and achieved a complete hematological response three weeks later. Although drug interactions between dasatinib and amiodarone were of concern, the blood concentration of each drug remained within the safe range after concomitant use, and there were no adverse cardiac effects such as QT prolongation after rechallenging dasatinib. Induction therapy with dasatinib and prednisolone may be an acceptable therapeutic option for Philadelphia chromosome-positive acute lymphoblastic leukemia with severe cardiac complications.

Application of Static Modeling --in the Prediction of In Vivo Drug-Drug Interactions between Rivaroxaban and Antiarrhythmic Agents Based on In Vitro Inhibition Studies

Rivaroxaban, a direct Factor Xa inhibitor, is indicated for stroke prevention in nonvalvular atrial fibrillation (AF). Studies have revealed that the clearance of rivaroxaban is largely attributed to CYP3A4, CYP2J2 metabolism, and P-glycoprotein (P-gp) efflux pathways. Amiodarone and dronedarone are antiarrhythmic agents employed in AF management. Amiodarone, dronedarone, and their major metabolites, N-desethylamiodarone (NDEA) and N-desbutyldronedarone (NDBD), demonstrate inhibitory effects on CYP3A4 and CYP2J2 with U.S. Food and Drug Administration-recommended probe substrates. In addition, both amiodarone and dronedarone are known P-gp inhibitors. Hence, the concomitant administration of these antiarrhythmic agents has the potential to augment the systemic exposure of rivaroxaban through simultaneous impairment of its clearance pathways. Currently, however, clinical data on the extent of these postulated drug-drug interactions are lacking. In this study, in vitro inhibition assays using rivaroxaban as the probe substrate demonstrated that both dronedarone and NDBD produced reversible inhibition as well as irreversible mechanism-based inactivation of CYP3A4- and CYP2J2-mediated metabolism of rivaroxaban. However, amiodarone and NDEA were observed to cause reversible inhibition as well as mechanism-based inactivation of CYP3A4 but not CYP2J2. In addition, amiodarone, NDEA, and dronedarone, but not NDBD, were determined to inhibit P-gp-mediated rivaroxaban transport. The in vitro inhibition parameters were fitted into a mechanistic static model, which predicted a 37% and 31% increase in rivaroxaban exposure due to the inhibition of hepatic and gut metabolism by amiodarone and dronedarone, respectively. A separate model quantifying the inhibition of P-gp-mediated efflux by amiodarone or dronedarone projected a 9% increase in rivaroxaban exposure.

Quantitative Prediction of Drug-Drug Interactions Involving Inhibitory Metabolites in Drug Development: How Can Physiologically Based Pharmacokinetic Modeling Help?

This subteam under the Drug Metabolism Leadership Group (Innovation and Quality Consortium) investigated the quantitative role of circulating inhibitory metabolites in drug-drug interactions using physiologically based pharmacokinetic (PBPK) modeling. Three drugs with major circulating inhibitory metabolites (amiodarone, gemfibrozil, and sertraline) were systematically evaluated in addition to the literature review of recent examples. The application of PBPK modeling in drug interactions by inhibitory parent-metabolite pairs is described and guidance on strategic application is provided.

Interaction between amiodarone and hepatitis-C virus nucleotide inhibitors in human induced pluripotent stem cell-derived cardiomyocytes and HEK-293 Cav1.2 over-expressing cells

Several clinical cases of severe bradyarrhythmias have been reported upon co-administration of the Hepatitis-C NS5B Nucleotide Polymerase Inhibitor (HCV-NI) direct-acting antiviral agent, sofosbuvir (SOF), and the Class-III anti-arrhythmic amiodarone (AMIO). We model the cardiac drug-drug interaction (DDI) between AMIO and SOF, and between AMIO and a closely-related SOF analog, MNI-1 (Merck Nucleotide Inhibitor #1), in functional assays of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), to provide mechanistic insights into recently reported clinical cases. AMIO co-applied with SOF or MNI-1 increased beating rate or field potential (FP) rate and decreased impedance (IMP) and Ca(2+) transient amplitudes in hiPSC-CM syncytia. This action resembled that of Ca(2+) channel blockers (CCBs) in the model, but CCBs did not substitute for AMIO in the DDI. AMIO analog dronedarone (DRON) did not substitute for, but competed with AMIO in the DDI. Ryanodine and thapsigargin, decreasing intracellular Ca(2+) stores, and SEA-0400, a Na(+)/Ca(2+) exchanger-1 (NCX1) inhibitor, partially antagonized or suppressed DDI effects. Other agents affecting FP rate only exerted additive or subtractive effects, commensurate with their individual effects. We also describe an interaction between AMIO and MNI-1 on Cav1.2 ion channels in an over-expressing HEK-293 cell line. MNI-1 enhanced Cav1.2 channel inhibition by AMIO, but did not affect inhibition of Cav1.2 by DRON, verapamil, nifedipine, or diltiazem. Our data in hiPSC-CMs indicate that HCV-NI agents such as SOF and MNI-1 interact with key intracellular Ca(2+)-handling mechanisms. Additional study in a Cav1.2 HEK-293 cell-line suggests that HCV-NIs potentiate the inhibitory action of AMIO on L-type Ca(2+) channels.

In Vitro Enhancement of Carvedilol Glucuronidation by Amiodarone-Mediated Altered Protein Binding in Incubation Mixture of Human Liver Microsomes with Bovine Serum Albumin

Carvedilol is mainly metabolized in the liver to O-glucuronide (O-Glu). We previously found that the glucuronidation activity of racemic carvedilol in pooled human liver microsomes (HLM) was increased, R-selectively, in the presence of amiodarone. The aim of this study was to clarify the mechanisms for the enhancing effect of amiodarone on R- and S-carvedilol glucuronidation. We evaluated O-Glu formation of R- and S-carvedilol enantiomers in a reaction mixture of HLM including 0.2% bovine serum albumin (BSA). In the absence of amiodarone, glucuronidation activity of R- and S-carvedilol for 25 min was 0.026, and 0.51 pmol/min/mg protein, and that was increased by 6.15 and 1.60-fold in the presence of 50 µM amiodarone, respectively. On the other hand, in the absence of BSA, or when BSA was replaced with human serum albumin, no enhancing effect of amiodarone on glucuronidation activity was observed, suggesting that BSA played a role in the mechanisms for the enhancement of glucuronidation activity. Unbound fraction of S-carvedilol in the reaction mixture was greater than that of R-carvedilol in the absence of amiodarone. Also, the addition of amiodarone caused a greater increase of unbound fraction of R-carvedilol than that of S-carvedilol. These results suggest that the altered protein binding by amiodarone is a key mechanism for R-selective stimulation of carvedilol glucuronidation.

The role of CYP 3A4 and 1A1 in amiodarone-induced hepatocellular toxicity

Amiodarone is a widely used potent antiarrhythmic for the treatment of cardiac disease; however, its use is often discontinued due to numerous adverse effects, including hepatotoxicity. To investigate the role of drug metabolism in this liver toxicity, amiodarone and its major metabolite desethylamiodarone were incubated with HepG2 cells overexpressing a series of cytochrome P450 (CYP) isoforms. Significantly higher cytotoxicity of amiodarone was observed in HepG2 cells overexpressing CYP3A4 or CYP1A1, compared with that observed in empty vector transduced control cells. Further, higher levels of the more potent hepatotoxic metabolite desethylamiodarone were detected in CYP3A4 or CYP1A1 expressed cells. The CYP3A4 inhibitor ketoconazole and the CYP1A1 inhibitor α-naphthoflavone drastically inhibited the metabolism of amiodarone to desethylamiodarone. Along with the inhibition of CYP1A1 or CYP3A4, the cytotoxicity of amiodarone was significantly reduced. These data indicate that the metabolism of amiodarone to desethylamiodarone by CYP1A1 or CYP3A4 plays an important role in the hepatocellular toxicity of amiodarone.