Amiodarone

Case Report: Amiodarone-induced multi-organ toxicity

Background

Amiodarone is a class III antiarrhythmic drug that is commonly used in the clinic to treat ventricular arrhythmias and atrial fibrillation. We present a case report of the adverse effects of amiodarone and review its characteristics.

Case report

A 73-year-old Asian female with a history of paroxysmal atrial fibrillation managed with amiodarone, well-controlled hypertension, and no substance abuse presented with gastrointestinal distress and dizziness, without chest pain or palpitations. Despite normal annual check-ups, she developed abnormal liver and thyroid function tests, and imaging revealed lung and liver changes suggestive of amiodarone toxicity. Discontinuation of amiodarone for sotalol led to symptom improvement and normalization of thyroid and liver functions, with imaging indicating recovery from interstitial fibrosis and reduced liver density.

Discussion

Amiodarone, a widely used for treating ventricular and atrial arrhythmias, and with significant benefits in improving patient survival in cases of ventricular fibrillation. However, its long-term use is associated with serious adverse effects, including thyroid dysfunction, liver injury, and pulmonary toxicity, necessitating careful monitoring and management. Despite its efficacy, the need for research on early detection and management of amiodarone's side effects is crucial, highlighting the importance of regular monitoring and possibly adjusting therapy to mitigate these risks.

Relevance of mexiletine in the era of evolving antiarrhythmic therapy of ventricular arrhythmias

Despite impressive developments in the field of ventricular arrhythmias, there is still a relevant number of patients with ventricular arrhythmias who require antiarrhythmic drug therapy and may, e.g., in otherwise drug and/or ablation refractory situations, benefit from agents known for decades, such as mexiletine. Through its capability of blocking fast sodium channels in cardiomyocytes, it has played a minor to moderate antiarrhythmic role throughout the recent decades. Nevertheless, certain patients with structural heart disease suffering from drug-refractory, i.e., mainly amiodarone refractory ventricular arrhythmias, as well as those with selected forms of congenital long QT syndrome (LQTS) may nowadays still benefit from mexiletine. Here, we outline mexiletine's cellular and clinical electrophysiological properties. In addition, the application of mexiletine may be accompanied by various potential side effects, e.g., nausea and tremor, and is limited by several drug-drug interactions. Thus, we shed light on the current therapeutic role of mexiletine for therapy of ventricular arrhythmias and discuss clinically relevant aspects of its indications based on current evidence.

The role of melatonin in preventing amiodarone-induced rat liver damage

Long-term exposure to amiodarone, an antiarrhythmic drug, can induce different organ damage, including liver. Cell damage included by amiodarone is a consequence of mitochondrial damage, reactive oxygen species production, and cell energy depletion leading to programmed cell death. In the present study, hepatoprotective potential of neurohormone melatonin (50 mg/kg/day) was evaluated in a chronic experimental model of liver damage induced by a 4-week application of amiodarone (70 mg/kg/day). The obtained results indicate that amiodarone induces an increase in xanthine oxidase activity, as well as the content of the lipid and protein oxidatively modified products and p53 levels. Microscopic analysis further corroborated the biochemical findings revealing hepatocyte degeneration, apoptosis, and occasional necrosis, with the activation of Kupffer cells. Coadministration of melatonin and amiodaron prevented an increase in certain damage associated parameters, due to its multiple targets. In conclusion, the application of melatonin together with amiodarone prevented an increase in tissue oxidative damage parameters and moderately prevented liver cell apoptosis, indicating that the damage of hepatocytes provoked by amiodarone supersedes the protective properties of melatonin in a given dose.

Amiodarone-Induced Nystagmus and Ataxia: Case Report and Systematic Review of Case Reports

Amiodarone is an antiarrhythmic drug with a significant adverse effect profile, including neurotoxicity. While ataxia, neuropathy, and tremors are more commonly seen forms of amiodarone neurotoxicity, very few cases of nystagmus are reported. We report the case of an 86-year-old man who presented with abrupt-onset ataxia, dizziness, and inability to ambulate, 10 days after initiating amiodarone for atrial fibrillation. His examination revealed gaze-evoked nystagmus along with features of cerebellar dysfunction. After excluding other etiologies, amiodarone was stopped. His nystagmus resolved, and his ataxia improved within 48 h of stopping amiodarone. Due to the rarity of this drug-induced adverse effect, we performed a systematic review of available case reports in the literature (PubMed and Scopus) using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and presented our findings. Nystagmus is a rarely reported adverse effect of amiodarone, which can occur within days to months of starting the medication. Treatment includes stopping the drug and monitoring for resolution of nystagmus.

Hepatic Encephalopathy Caused by Long-Term Amiodarone Use

This case describes a 72-year-old Japanese woman with hypertrophic cardiomyopathy and non-sustained ventricular tachycardia who had received a total of 215 g of amiodarone over six years and presented with hepatic encephalopathy. The abdominal non-contrast computed tomography showed diffusely increased attenuation of the liver parenchyma. The liver biopsy revealed drug-induced steatohepatitis. No genetic variations in the urea cycle were found. She was ultimately diagnosed with drug-induced steatohepatitis and urea cycle abnormalities caused by long-term amiodarone use. Amiodarone may cause drug-induced steatohepatitis and urea cycle abnormalities, which could induce hyperammonemia. Although case reports of amiodarone-induced hyperammonemia and hepatic encephalopathy have already been reported, we present a typical picture of an amiodarone-induced bright liver, including the mechanism of amiodarone-induced hyperammonemia, to provide an educational learning point for many readers.

Clinical and economic outcomes associated with use of anti-arrhythmic drugs versus ablation in atrial fibrillation

Aim: To evaluate the clinical and economic impact of antiarrhythmic drugs (AADs) compared with ablation both as individual treatments and as combination therapy without/with considering the order of treatment among patients with atrial fibrillation (AFib). Materials & methods: A budget impact model over a one-year time horizon was developed to assess the economic impact of AADs (amiodarone, dofetilide, dronedarone, flecainide, propafenone, sotalol, and as a group) versus ablation across three scenarios: direct comparisons of individual treatments, non-temporal combinations, and temporal combinations. The economic analysis was conducted in accordance with CHEERS guidance as per current model objectives. Results are reported as costs per patient per year (PPPY). The impact of individual parameters was evaluated using one-way sensitivity analysis (OWSA). Results: In direct comparisons, ablation had the highest annual medication/procedure cost ($29,432), followed by dofetilide ($7661), dronedarone ($6451), sotalol ($4552), propafenone ($3044), flecainide ($2563), and amiodarone ($2538). Flecainide had the highest costs for long-term clinical outcomes ($22,964), followed by dofetilide ($17,462), sotalol ($15,030), amiodarone ($12,450), dronedarone ($10,424), propafenone ($7678) and ablation ($9948). In the non-temporal scenario, total costs incurred for AADs (group) + ablation ($17,278) were lower compared with ablation alone ($39,380). In the temporal scenario, AADs (group) before ablation resulted in PPPY cost savings of ($22,858) compared with AADs (group) after ablation ($19,958). Key factors in OWSA were ablation costs, the proportion of patients having reablation, and withdrawal due to adverse events. Conclusion: Utilization of AADs as individual treatment or in combination with ablation demonstrated comparable clinical benefits along with costs savings in patients with AFib.

Antiarrhythmic Drug Therapy in Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heritable progressive myocardial disorder that predisposes patients to ventricular arrhythmias and sudden cardiac death. Antiarrhythmic medications have an important role in reducing the frequency of ventricular arrhythmias and the morbidity associated with recurrent implantable cardioverter-defibrillator (ICD) shocks. Although several studies have examined the use of antiarrhythmic drugs in ARVC, these have been mostly retrospective in nature and inconsistent in their methodology, patient population and endpoints. Thus, current prescribing practices are largely based on expert opinion and extrapolation from other diseases. Herein, we discuss the major studies of the use of antiarrhythmics in ARVC, present the current approach employed at the Johns Hopkins Hospital and identify areas where further research is needed. Most notably, there is a great need for high-quality studies with consistent methodology and randomized controlled trial data into the use of antiarrhythmic drugs in ARVC. This would improve management of the condition and ensure antiarrhythmic prescribing is based on robust evidence.

Development of Interstitial Lung Disease Among Patients With Atrial Fibrillation Receiving Oral Anticoagulants in Taiwan

IMPORTANCE

There are emerging concerns from case reports and pharmacovigilance analyses of a possible risk of interstitial lung disease (ILD) associated with the use of factor Xa (FXa) inhibitors.

OBJECTIVE

To evaluate the risk of incident ILD associated with the use of oral anticoagulants (OACs) in patients with nonvalvular atrial fibrillation (NVAF).

DESIGN, SETTING, AND PARTICIPANTS

This nationwide retrospective cohort study used data from the Taiwan National Health Insurance Research Database. Patients with NVAF without preexisting lung disease who received OACs from June 1, 2012, to December 31, 2017, were included. Propensity score stabilized weighting (PSSW) was used to balance covariates across the medication groups (FXa inhibitors, dabigatran, and warfarin, with warfarin as the reference). Patients were followed up from the drug index date until the onset of ILD, death, or end of the study (December 31, 2019), whichever occurred first. Data were analyzed from September 11, 2021, to August 3, 2022.

EXPOSURES

Patients with NVAF were treated with FXa inhibitors, dabigatran, or warfarin.

MAIN OUTCOMES AND MEASURES

New-onset idiopathic ILD.

RESULTS

Among the 106 044 patients (mean [SD] age, 73.4 [11.9] years; 59 995 men [56.6%]) included in the study, 64 555 (60.9%) received FXa inhibitors (apixban [n = 15 386], edoxaban [n = 12 413], and rivaroxaban [n = 36 756]), 22 501 (21.2%) received dabigatran, and 18 988 (17.9%) received warfarin at baseline. The FXa inhibitors were associated with a higher risk of incident ILD (0.29 vs 0.17 per 100 patient-years; hazard ratio, 1.54 [95% CI, 1.22-1.94]; P < .001), whereas dabigatran was associated with a nonsignificant difference in risk of incident ILD compared with warfarin (reference) after PSSW. The higher risk of incident ILD for FXa inhibitors vs warfarin was consistent with several high-risk subgroups.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that FXa inhibitors were associated with lung injury among patients with NVAF who were treated with OACs. Physicians should be vigilant in monitoring for any potential adverse lung outcomes associated with the use of these drugs.

Griseofulvin: An Updated Overview of Old and Current Knowledge

Griseofulvin is an antifungal polyketide metabolite produced mainly by ascomycetes. Since it was commercially introduced in 1959, griseofulvin has been used in treating dermatophyte infections. This fungistatic has gained increasing interest for multifunctional applications in the last decades due to its potential to disrupt mitosis and cell division in human cancer cells and arrest hepatitis C virus replication. In addition to these inhibitory effects, we and others found griseofulvin may enhance ACE2 function, contribute to vascular vasodilation, and improve capillary blood flow. Furthermore, molecular docking analysis revealed that griseofulvin and its derivatives have good binding potential with SARS-CoV-2 main protease, RNA-dependent RNA polymerase (RdRp), and spike protein receptor-binding domain (RBD), suggesting its inhibitory effects on SARS-CoV-2 entry and viral replication. These findings imply the repurposing potentials of the FDA-approved drug griseofulvin in designing and developing novel therapeutic interventions. In this review, we have summarized the available information from its discovery to recent progress in this growing field. Additionally, explored is the possible mechanism leading to rare hepatitis induced by griseofulvin. We found that griseofulvin and its metabolites, including 6-desmethylgriseofulvin (6-DMG) and 4- desmethylgriseofulvin (4-DMG), have favorable interactions with cytokeratin intermediate filament proteins (K8 and K18), ranging from -3.34 to -5.61 kcal mol-1. Therefore, they could be responsible for liver injury and Mallory body (MB) formation in hepatocytes of human, mouse, and rat treated with griseofulvin. Moreover, the stronger binding of griseofulvin to K18 in rodents than in human may explain the observed difference in the severity of hepatitis between rodents and human.

Quantitation of Free Thyroxine by Equilibrium Dialysis and Liquid Chromatography-Tandem Mass Spectrometry

A method for free thyroxine measurement in human serum using equilibrium dialysis followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) is described. Free thyroxine in serum is first separated from protein-bound thyroxine by equilibrium dialysis and then measured by LC-MS/MS.

Historical Aspects of the Use of Antiarrhythmic Drugs in Clinical Practice

Heart rhythm disorders are one of the most urgent problems in cardiology. The first reports on the possibility of using drugs in the treatment of cardiac arrhythmias began to appear in the scientific literature from the middle of the 18th century. This pharmacotherapeutic direction has been developed since the second half of the 20th century, when new antiarrhythmic drugs began to be used in clinical practice. The introduction of new drugs and modern methods of treating arrhythmias into clinical practice has significantly improved the prognosis and quality of life of patients. Combination antiarrhythmic therapy, including antiarrhythmic drugs and radiofrequency ablation, seems to be the most promising and successful tactic for treating patients in the future. A historical review of the literature on the clinical use of antiarrhythmic drugs both in past years and at present is presented in the article.

Drug Interactions Affecting Antiarrhythmic Drug Use

Antiarrhythmic drugs (AAD) play an important role in the management of arrhythmias. Drug interactions involving AAD are common in clinical practice. As AADs have a narrow therapeutic window, both pharmacokinetic as well as pharmacodynamic interactions involving AAD can result in serious adverse drug reactions ranging from arrhythmia recurrence, failure of device-based therapy, and heart failure, to death. Pharmacokinetic drug interactions frequently involve the inhibition of key metabolic pathways, resulting in accumulation of a substrate drug. Additionally, over the past 2 decades, the P-gp (permeability glycoprotein) has been increasingly cited as a significant source of drug interactions. Pharmacodynamic drug interactions involving AADs commonly involve additive QT prolongation. Amiodarone, quinidine, and dofetilide are AADs with numerous and clinically significant drug interactions. Recent studies have also demonstrated increased morbidity and mortality with the use of digoxin and other AAD which interact with P-gp. QT prolongation is an important pharmacodynamic interaction involving mainly Vaughan-Williams class III AAD as many commonly used drug classes, such as macrolide antibiotics, fluoroquinolone antibiotics, antipsychotics, and antiemetics prolong the QT interval. Whenever possible, serious drug-drug interactions involving AAD should be avoided. If unavoidable, patients will require closer monitoring and the concomitant use of interacting agents should be minimized. Increasing awareness of drug interactions among clinicians will significantly improve patient safety for patients with arrhythmias.

Development of a Scoring System to Differentiate Amiodarone-Induced Liver Injury From Alcoholic Steatohepatitis

OBJECTIVES

Amiodarone-induced liver injury (AILI) is histopathologically similar to alcoholic steatohepatitis (ASH). We sought to elucidate their histologic differences and develop a scoring system to differentiate these two entities.

METHODS

A cohort of 17 AILI and 17 ASH cases was included in the initial study. Cases from three different institutions were included for further validation.

RESULTS

Macrovesicular steatosis was usually below 10% of the liver parenchyma in AILI. Hepatocyte ballooning degeneration was more common in ASH than in AILI. "Balloon-like" hepatocyte was more common in AILI than in ASH. Lobular neutrophilic inflammation, satellitosis, and cholestasis were more common in ASH. Mallory-Denk bodies and pericellular fibrosis in AILI were mainly located in zone 1 compared with a panacinar or zone 3 distribution in ASH. A scoring system was developed in which points were assigned to different histologic features; a total sum of less than 5 suggests AILI, more than 5 is ASH, and 5 is equivocal. This scoring system was then evaluated on a test cohort comprising 14 AILI cases, in which 13 cases were correctly assigned with a score less than 5. The sensitivity, specificity, and accuracy for diagnosing AILI in the test cohort were 92.9%, 91.7%, and 92.3%, respectively.

CONCLUSIONS

This scoring system can aid pathologists to differentiate AILI from ASH.

Amiodarone-Induced Multi-Systemic Toxicity Involving the Liver, Lungs, Thyroid, and Eyes: A Case Report

Objectives

Amiodarone is widely used to treat arrhythmia. However, amiodarone is known for its severe toxicity to the liver, lungs, and thyroid. Amiodarone causes liver damage ranging from asymptomatic serum aminotransferase elevation to hepatic failure requiring liver transplantation. Although amiodarone toxicity has been reported, its simultaneous multi-organ toxicity is not well-known. Here, we introduce a novel case of multi-systemic amiodarone toxicity involving the liver, lungs, thyroid, and eyes.

Case Presentation

A 61-year-old woman visited the emergency room due to general weakness, nausea, visual disturbance, heat intolerance, and a non-productive cough. The patient had been using clopidogrel and amiodarone due to underlying atrial fibrillation. The total level of bilirubin was 0.71 mg/dL, aspartate aminotransferase was 358 U/L, alanine aminotransferase was 177 U/L, and prothrombin time was 27.1 s. Computed tomography showed diffuse increased liver intensity and scattered hyperattenuated nodular consolidations in both lungs. Transthoracic needle lung biopsy revealed fibrinoid interstitial inflammation with atypical change of type II pneumocytes and intra-alveolar foamy macrophages. In addition, the thyroid-stimulating hormone level was &lt;0.008 μIU/mL, and free thyroxine was 4.67 ng/dL. The thyroid scan showed diffuse homogenous intake of technetium-99 m pertechnetate in both thyroid lobes. The ophthalmologic exam detected bilateral symmetrical corneal deposits in a vortex pattern. With these findings, we could diagnose amiodarone-induced hepatic, pulmonary, thyroid, and ophthalmologic toxicity. Liver function was restored after cessation of amiodarone, and thyroid function was normalized with methimazole administration. However, due to aggravated lung consolidations, systemic steroid treatment was administered, and improvement was seen 1 week after, at the follow-up exam. As her symptoms improved, she was discharged with a plan of steroid administration for 3 to 6 months.

Conclusions

This case implies the possibility of multi-systemic amiodarone toxicity. Thus, the toxicity of amiodarone to multiple organs must be monitored. Prompt cessation of the drug should be considered upon diagnosis.

Recent insights into mechanisms and clinical approaches to electrical storm

Electrical storm, characterized by repetitive ventricular tachycardia/fibrillation (VT/VF) over a short period, is becoming commoner with widespread use of implantable cardioverter-defibrillator (ICD) therapy. Electrical storm, sometimes called "arrhythmic storm" or "VT-storm", is usually a medical emergency requiring hospitalization and expert management, and significantly affects short- and long-term outcomes. This syndrome typically occurs in patients with underlying structural heart disease (ischemic or non-ischemic cardiomyopathy) or inherited channelopathies. Triggers for electrical storm should be sought but are often unidentifiable. Initial management is dictated by the hemodynamic status, while subsequent management typically involves ICD interrogation and reprogramming to reduce recurrent shocks, identification/management of triggers like electrolyte abnormalities, myocardial ischemia, or decompensated heart failure, and antiarrhythmic-drug therapy or catheter ablation. Sympathetic nervous system activation is central to the initiation and maintenance of arrhythmic storm, so autonomic modulation is a cornerstone of management. Sympathetic inhibition can be achieved with medications (particularly beta-adrenoreceptor blockers), deep sedation, or cardiac sympathetic denervation. More definitive management targets the underlying ventricular arrhythmia substrate to terminate and prevent recurrent arrhythmia. Arrhythmia targeting can be achieved with antiarrhythmic medications, catheter ablation or more novel therapies such as stereotactic radiation therapy that targets the arrhythmic substrate. Mechanistic studies point to adrenergic activation and other direct consequences of ICD-shocks in promoting further arrhythmogenesis and hypocontractility. Here, we review the pathophysiologic mechanisms, clinical features, prognosis, and therapeutic options for electrical storm. We also outline a clinical approach to this challenging and complex condition, along with its mechanistic basis.

Electrical storm: Prognosis and management

Electrical storm is present when a cluster of ventricular arrhythmias (VAs) occurs within a short time frame. The most widely accepted definition is 3 or more episodes of VA within a 24-h period, although prognostic risk begins to rise when 2 or more events occur within 3months. Electrical storm often presents as a medical emergency in the form of recurrent implantable cardiac defibrillator (ICD) shocks, recurrent syncope in patients with no ICD or low cardiac output symptoms. Management often requires a multimodality approach including ICD management, pharmacologic therapy, catheter ablation and modulations of the autonomic nervous system. In this article, we review the definition, prognosis and management of electrical storm.

[Perioperative Atrial Fibrillation]

New atrial fibrillation is a risk factor for increased morbidity and mortality in the perioperative phase. The prevalence and incidence of atrial fibrillation depend on age, previous illnesses and the intercurrent diagnoses in the perioperative phase. Pathomechanisms for both permanent and acute forms of atrial fibrillation relate to electrophysiological, histopathological and other pathophysiological abnormalities. In the perioperative phase, decompensated heart failure, systemic inflammation, sepsis and cardiac surgery are risk factors for conversion to atrial fibrillation and/or rapid transition. The consequences of newly occurring and/or rapidly transferred atrial fibrillation are cardiac instability due to a drop in blood pressure or cardiac output volume or coronary underperfusion due to tachycardia and the risk of thromboembolism. Associated with this is a significantly increased long-term mortality risk in the elderly if atrial fibrillation occurs again in the perioperative phase. The diagnosis of atrial fibrillation is made in the monitor or 12-channel electrocardiogram. Echocardiography and the adenosine test can be included in the differential diagnosis in cases of doubt. Important current guidelines for the treatment of atrial fibrillation are the ESC (atrial fibrillation) and the ERC (Advanced Cardiac Life Support) guidelines. The conversion into the sinus rhythm can be done electrically or medicinally. It is indicated in cases of acute instability or symptomatic atrial fibrillation despite frequency control after cardiac thrombi have been excluded by echocardiography. A step-by-step concept for thromboembolism prophylaxis from initial parenteral and secondary oral therapy must take place up to four weeks after conversion to sinus rhythm or permanently in the case of permanent atrial fibrillation. The individual indication for thromboembolism prophylaxis results from the CHA2-DS2-VASc score.

Amiodarone-Induced Immune Thrombocytopenia: A Rare Hematologic Side Effect of a Common Cardiac Drug

Thrombocytopenia is a rare immune-mediated hematologic complication of amiodarone. We describe a case of delayed-onset amiodarone-induced thrombocytopenia in a 72-year-old male and highlight the process of working it up. A timely diagnosis of drug-induced immune thrombocytopenia is crucial in order to minimize unnecessary testing, avoid treatments with potential harm, and prevent life-threatening hemorrhagic complications.

Aldehydes: magnificent acyl equivalents for direct acylation

From the viewpoint of meeting the current green chemistry challenges in chemical synthesis, there is a need to disseminate how the cocktail of acylation and activation can play a pivotal role in affording bioactive acylated products comprising substituted ketone motifs in fewer reaction steps, with higher atom-economy and improved selectivity. In recent years, a significant number of articles employing the title compounds "aldehydes" as magnificent acylation surrogates which are less toxic and widely applicable have been published. This review sheds light on the compounds use for selective acylation of arene, heteroarene and alkyl (sp3, sp2 and sp) C-H bonds by proficient utilization of the C-H activation strategy. Critical insights into selective acylation of diverse moieties for the synthesis of bioactive compounds are presented in this review that will enable academic and industrial researchers to understand the mechanistic aspects involved and fruitfully employ these strategies in designing novel molecules.

Recent Achievement in the Synthesis of Benzo[b]furans

BACKGROUND

Benzo[b]furan derivatives are oxygen-containing heterocyclic compounds consisting of fused benzene and furan rings and are present in a large number of natural and non-natural compounds. This class of compounds has a wide spectrum of biological activities, such as antiarrhythmic, anticancer, inflammatory, antioxidant, antimicrobial, and antiviral. Furthermore, benzo[b]furan derivatives have also been applied in various areas, such as organic electroluminescence device materials and organic dyes, photosensitizing material, organic synthesis as building blocks or intermediates. Because of a broad range of applicability, the synthesis of benzo[b]furan derivative has drawn great attention of chemists and many studies on the synthesis of this class of compounds have been reported recently. This review will give an overview of benzo[b]furan preparation based on studies dating back to the year 2012.

OBJECTIVE

In this review, recent development in the synthesis of benzo[b]furans are discussed. There has been increasingly new methodologies for the construction of benzo[b]furans skeleton to improve efficiency or develop environmentally friendly procedures. In some studies, reaction mechanisms were also outlined.

CONCLUSION

Many methods for the synthesis of benzo[b]furans have been reported recently. Most of them involve cyclization or cycloisomerization processes. Unquestionably, more imaginative strategies for the construction of benzo[b]furan skeleton will be established in the near future. Application of known methods to natural products or drug synthesis, on industrial scale for the synthesis of economically or medicinally important benzo[ b]furans will probably be paid attention to.

Handling of Ventricular Fibrillation in the Emergency Setting

Ventricular fibrillation (VF) and sudden cardiac death (SCD) are predominantly caused by channelopathies and cardiomyopathies in youngsters and coronary heart disease in the elderly. Temporary factors, e.g., electrolyte imbalance, drug interactions, and substance abuses may play an additive role in arrhythmogenesis. Ectopic automaticity, triggered activity, and reentry mechanisms are known as important electrophysiological substrates for VF determining the antiarrhythmic therapies at the same time. Emergency need for electrical cardioversion is supported by the fact that every minute without defibrillation decreases survival rates by approximately 7%–10%. Thus, early defibrillation is an essential part of antiarrhythmic emergency management. Drug therapy has its relevance rather in the prevention of sudden cardiac death, where early recognition and treatment of the underlying disease has significant importance. Cardioprotective and antiarrhythmic effects of beta blockers in patients predisposed to sudden cardiac death were highlighted in numerous studies, hence nowadays these drugs are considered to be the cornerstones of the prevention and treatment of life-threatening ventricular arrhythmias. Nevertheless, other medical therapies have not been proven to be useful in the prevention of VF. Although amiodarone has shown positive results occasionally, this was not demonstrated to be consistent. Furthermore, the potential proarrhythmic effects of drugs may also limit their applicability. Based on these unfavorable observations we highlight the importance of arrhythmia prevention, where echocardiography, electrocardiography and laboratory testing play a significant role even in the emergency setting. In the following we provide a summary on the latest developments on cardiopulmonary resuscitation, and the evaluation and preventive treatment possibilities of patients with increased susceptibility to VF and SCD.

Atrial Fibrillation Post Coronary Artery Graft Surgery: A Review Of Literature

Atrial fibrillation (AF) is a failure that is observed in heart disease and is also known to be the most common heart rhythm disturbance post coronary artery bypass surgery. Although AF is considered a transient problem, it is usually accompanied with a variety of complications and morbidity for patients and may result in death. In the present study, pre- and post-operative considerable factors which may increase the risk and mortality of AF, and possible treatments have been concisely reviewed.

Natural source, bioactivity and synthesis of benzofuran derivatives

Benzofuran compounds are a class of compounds that are ubiquitous in nature. Numerous studies have shown that most benzofuran compounds have strong biological activities such as anti-tumor, antibacterial, anti-oxidative, and anti-viral activities. Owing to these biological activities and potential applications in many aspects, benzofuran compounds have attracted more and more attention of chemical and pharmaceutical researchers worldwide, making these substances potential natural drug lead compounds. For example, the recently discovered novel macrocyclic benzofuran compound has anti-hepatitis C virus activity and is expected to be an effective therapeutic drug for hepatitis C disease; novel scaffold compounds of benzothiophene and benzofuran have been developed and utilized as anticancer agents. Novel methods for constructing benzofuran rings have been discovered in recent years. A complex benzofuran derivative is constructed by a unique free radical cyclization cascade, which is an excellent method for the synthesis of a series of difficult-to-prepare polycyclic benzofuran compounds. Another benzofuran ring constructed by proton quantum tunneling has not only fewer side reactions, but also high yield, which is conducive to the construction of complex benzofuran ring systems. This review summarizes the recent studies on the various aspects of benzofuran derivatives including their important natural product sources, biological activities and drug prospects, and chemical synthesis, as well as the relationship between the bioactivities and structures.

Effects of N-acetyl cysteine, vitamin E and vitamin C on liver glutathione levels following amiodarone treatment in rats

Introduction

Amiodarone, a pharmaceutical extensively used to suppress atrial and ventricular tachyarrhythmias, is also known to cause many side effects on many tissues. N-acetyl-cysteine (NAC), vitamin E and vitamin C are known as antioxidants for their ability to minimize oxidative stress. In the peer-reviewed literature, there is no study reporting on the protective effects of these antioxidant agents against its hepatotoxicity.

Aim

We investigated the oxidative effects of NAC, vitamins E and C on liver tissue after amiodarone treatment.

Material and methods

Rats were randomly assigned to: control; amiodarone group; amiodarone + NAC treated group; amiodarone + Vit. E group and amiodarone + Vit. C group. Liver tissues were isolated from animals and total glutathione levels were measured.

Results

In all time intervals, the level of glutathione increased. When all time intervals were compared, the amiodarone group revealed the lowest levels. The antioxidant co-administered group was studied; the glutathione levels were statistically significantly higher than the sole amiodarone group. When vitamins E, C or N-acetyl cysteine were examined, there was no statistically significant difference among them.

Conclusions

In this study we found that hepatotoxicity capacity of amiodarone may be reduced by taking up antioxidants. In addition, the effect documented here may be reproducible and may be applied to clinical settings.

Generation of Human iPSC-Derived Intestinal Epithelial Cell Monolayers by CDX2 Transduction

BACKGROUND & AIMS

To develop an effective and safe orally administered drug, it is important to predict its intestinal absorption rate, intestinal first-pass effect, and drug-drug interactions of orally administered drugs. However, there is no existing model to comprehensively predict the intestinal pharmacokinetics and drug-response of orally administered drugs. In this study, we attempted to generate homogenous and functional intestinal epithelial cells from human induced pluripotent stem (iPS) cells for pharmaceutical research.

METHODS

We generated almost-homogenous Villin- and zonula occludens-1 (ZO1)-positive intestinal epithelial cells by caudal-related homeobox transcription factor 2 (CDX2) transduction into human iPS cell-derived intestinal progenitor cells.

RESULTS

The drug absorption rates in human iPS cell-derived intestinal epithelial cell monolayers (iPS-IECM) were highly correlated with those in humans (R²=0.91). The expression levels of cytochrome P450 (CYP) 3A4, a dominant drug-metabolizing enzyme in the small intestine, in human iPS-IECM were similar to those in human small intestine in vivo. In addition, intestinal availability in human iPS-IECM (the fraction passing the gut wall: Fg=0.73) was more similar to that in the human small intestine in vivo (Fg=0.57) than to that in Caco-2 cells (Fg=0.99), a human colorectal adenocarcinoma cell line. Moreover, the drug-drug interaction and drug-food interaction could be observed by using our human iPS-IECM in the presence of an inducer and inhibitor of CYP3A4, i.e., rifampicin and grape fruit juice, respectively.

CONCLUSION

Taking these results together, we succeeded in generating the human iPS-IECM that can be applied to various intestinal pharmacokinetics and drug-response tests of orally administered drugs.

A Stretchable and Flexible Cardiac Tissue-Electronics Hybrid Enabling Multiple Drug Release, Sensing, and Stimulation

Replacement of the damaged scar tissue created by a myocardial infarction is the goal of cardiac tissue engineering. However, once the implanted tissue is in place, monitoring its function is difficult and involves indirect methods, while intervention necessarily requires an invasive procedure and available medical attention. To overcome this, methods of integrating electronic components into engineered tissues have been recently presented. These allow for remote monitoring of tissue function as well as intervention through stimulation and controlled drug release. Here, an improved hybrid microelectronic tissue construct capable of withstanding the dynamic environment of the beating heart without compromising electronic or mechanical functionality is reported. While the reported system is enabled to sense the function of the engineered tissue and provide stimulation for pacing, an electroactive polymer on the electronics enables it to release multiple drugs in parallel. It is envisioned that the integration of microelectronic devices into engineered tissues will provide a better way to monitor patient health from afar, as well as provide facile, more exact methods to control the healing process.

Aggravation of atrial arrhythmia by amiodarone during the perinatal period: A case report

RATIONALE

Amiodarone, a broad-spectrum antiarrhythmic drug, is widely used for the clinical treatment of tachyarrhythmias because of its safety and efficacy.

PATIENT CONCERNS

A 30-year-old woman presented with known paroxysmal atrial tachycardia and severe preeclampsia. Two days before admission, she had given birth to twins. She described her symptoms as a sudden palpitation at 10:20 accompanied by chest tightness and shortness of breath.

DIAGNOSIS

Cardiac arrhythmia and acute left heart failure.

INTERVENTIONS

Furosemide and sodium nitroprusside were administered to control the heart failure. At 16:20, 150 mg amiodarone (15 mg/min) was injected intravenously and continued at 1 mg/min. At 16:50, her electrocardiogram showed possible atrial tachycardia or atrial flutter with a ventricular rate of 206 beats/min. Administration of amiodarone was stopped at 17:23, and the medication was changed to esmolol.

OUTCOMES

After 3 minutes, the palpitations stopped, the heart rate changed to a sinus rhythm, and the ventricular rate was 100 beats/min. Four days later, the patient underwent an electrophysiologic study and radiofrequency ablation.

LESSONS

When amiodarone is used to treat atrial arrhythmia, the ventricular rate may accelerate, which can cause patients with borderline heart failure to develop acute heart failure or further deterioration of acute heart failure. For heart failure induced or mediated by atrial arrhythmias, short-term β-blockers may be used to control the ventricular rate more quickly and effectively and to prevent the progression of heart failure.

[Clinical aspects of treatment with amiodarone]

Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.

Comedication with interacting drugs predisposes amiodarone users in cardiac and surgical intensive care units to acute liver injury: A retrospective analysis

Risk factors and underlying mechanisms for liver injury associated with amiodarone remain elusive. This study aimed to investigate the drug-related covariates for acute liver injury by amiodarone-an intriguing compound of high lipophilicity, with a long half-life and notable efficacy.The medical, pharmacy, and laboratory records of new amiodarone users admitted to the cardiac or surgical intensive care units of a medical center were examined retrospectively. A Cox regression model with time-varying dose-related variables of amiodarone was utilized to estimate the hazard ratio (HR) of amiodarone-associated liver injury while adjusting for concomitant therapy and relevant covariates.Of the 131 eligible patients among 6,572 amiodarone users (46,402 prescriptions), 6 were identified as amiodarone-associated liver injury cases. In comparison to controls (n = 125), this liver injury cohort (n = 6) had significantly higher numbers of amiodarone-interacting (2.7 ± 2.0 vs 0.9 ± 0.9 drugs, P = .02) and hepatotoxic (3.8 ± 0.8 vs 2.5 ± 1.7 drugs, P = .03) comedications. The number of comedications with amiodarone-interacting potential (HR 2.07, 95% confidence interval [CI] 1.02-4.22, P = .04) and amiodarone cumulative doses standardized by body surface area (HR 6.82, 95% CI 1.72-27.04, P = .01) were independent risk factors for liver injury associated with amiodarone.Drug-related (amiodarone cumulative dose, interacting drugs) factors were significant predictors of amiodarone-associated acute liver injury. A prudent evaluation of each medication profile is warranted to attain precision medicine at the level of patient care, especially for those treated by medications with complex physicochemical and pharmacokinetic properties, such as amiodarone.

Efficacy and Safety of Low-Dose Amiodarone Therapy for Tachyarrhythmia in Congenital Heart Disease

Amiodarone (AMD) is a class III anti-arrhythmic drug that is highly effective for tachyarrhythmia treatment. AMD is widely used in adults with congenital heart disease (CHD); however, higher doses of AMD (> 200 mg/day) can cause various non-cardiac side effects. The purpose of this study was to assess the efficacy, safety, and adverse events of low-dose AMD (≤ 200 mg/day) for tachyarrhythmia in patients with CHD. We retrospectively studied 80 patients with CHD and tachyarrhythmia who received oral low-dose AMD (≤ 200 mg/day) from January 2004 to March 2016. Low-dose AMD therapy was used to treat supraventricular tachycardia (SVT) in 51 patients and ventricular tachycardia (VT) in 29 patients. After a mean follow-up of 2.9 years for SVT and 3.2 years for VT, 36% and 65% of the patients with SVT and VT, respectively, were free from a first tachyarrhythmia recurrence for 3 years. The incidence of AMD-induced side effects was 23%, and all these cases consisted of thyroid dysfunction. Low-dose AMD was effective for the treatment of tachyarrhythmia in patients with CHD and had a relatively low incidence of side effects. These findings suggest that low-dose AMD is useful and effective for decreasing the frequency of tachyarrhythmia in patients with CHD and has a low incidence of side effects.

DNA damage-induced apoptosis and mitogen-activated protein kinase pathway contribute to the toxicity of dronedarone in hepatic cells

Dronedarone, an antiarrhythmic drug, has been marketed as an alternative to amiodarone. The use of dronedarone has been associated with severe liver injury; however, the mechanisms remain unclear. In this study, the possible mechanisms of dronedarone induced liver toxicity were characterized in HepG2 cells. Dronedarone decreased cells viability and induced apoptosis and DNA damage in a concentration- and time-dependent manner. Pretreatment of the HepG2 cells with apoptosis inhibitors (caspase-3, -8, and -9) or the necrosis inhibitor (Necrox-5), partially, but significantly, reduced the release of lactate dehydrogenase. Dronedarone caused the release of cytochrome c from mitochondria to cytosol, a prominent feature of apoptosis. In addition, the activation of caspase-2 was involved in dronedarone induced DNA damage and the activation of JNK and p38 signaling pathways. Inhibition of JNK and p38 by specific inhibitors attenuated dronedarone-induced cell death, apoptosis, and DNA damage. Additionally, suppression of caspase-2 decreased the activities of JNK and p38. Dronedarone triggered DNA damage was regulated by downregulation of topoisomerase IIα at both transcriptional and post-transcriptional levels. Taken together, our data show that DNA damage, apoptosis, and the activation of JNK and p38 contribute to dronedarone-induced cytotoxicity. Environ. Mol. Mutagen. 59:278-289, 2018. © 2018 Wiley Periodicals, Inc.

Amiodarone-induced thyrotoxicosis in heart failure with a reduced ejection fraction: A retrospective cohort study

BACKGROUND

Amiodarone-induced thyrotoxicosis (AIT) is associated with significant morbidity and mortality. We aimed to describe AIT and its clinical outcomes in patients with heart failure with reduced ejection fraction (HFrEF).

METHODS

We performed a retrospective chart review at a heart failure center in Winnipeg, Canada. We screened 1059 consecutive patients seen over a 12-month period (August 2011 to July 2012) for AIT in patients with HFrEF. Using descriptive and Cox proportional hazard analyses, we explored the association between AIT and mortality.

RESULTS

A total of 110 patients with HFrEF who were exposed to amiodarone were included in the analysis. Of these, 13 (11.8%) were diagnosed with AIT. All AIT patients in our cohort were male. Amiodarone was discontinued in nearly half (46.2%) of patients with AIT. All patients were treated with antithyroid medications, and 5 patients (38.5%) also received prednisone. Euthyroidism was achieved in 2 patients (15.4%), hypothyroidism occurred in 6 patients (46.2%), and 5 patients remained thyrotoxic until death or time of chart review (38.5%).

CONCLUSION

Thyrotoxicosis is common in patients with HFrEF on amiodarone and is challenging to treat. Due to the sample size, while no association was found in mortality for patients with HFrEF with AIT, a real association could have been missed.

Amiodarone-induced reversible and irreversible hepatotoxicity: two case reports

Background

Amiodarone is a highly effective treatment for supraventricular and ventricular tachyarrhythmia; however, it could be associated with several serious adverse effects, including liver injury.

Case presentation

We report the clinical and histological features of two contrasting Japanese patients with amiodarone-induced reversible and irreversible hepatotoxicity. One patient with amiodarone-induced irreversible hepatotoxicity showed liver cirrhosis during treatment with amiodarone and died of hepatic failure; the other patient, who had reversible hepatotoxicity, showed a reversible course of liver function and imaging after discontinuation of amiodarone.

Conclusions

We emphasize the importance of close monitoring of liver enzymes and evaluation of liver computed tomographic imaging as well as liver biopsy during treatment with amiodarone, and discontinuation should be considered when amiodarone-induced hepatotoxicity is suspected.

The effect of amiodarone on warfarin anticoagulation: a register-based nationwide cohort study involving the Swedish population

Essentials Data on the effect of introducing amiodarone in patients already using warfarin regime are scarce. Information on 754 patients was extracted from three nationwide registers in Sweden. With amiodaron, 37% of patients had an international normalized ratio (INR) over 3.0 To avoid bleeding, the initiation of amiodarone should be accompanied by closer INR monitoring.

SUMMARY

Background Data indicate that the interaction between warfarin and amiodarone results in an increased warfarin effect. There are several large, well-performed studies using genetic and clinical factors such as co-medication to predict an adequate starting dose of warfarin. However, longitudinal data on the effect of introducing amiodarone in patients on an ongoing warfarin regime are more scarce. Objectives An investigation of how initiation of amiodarone affects the anticoagulant effect and dosing of warfarin, using data from three nationwide registries. Patients/Methods In a retrospective cohort study including 754 patients, warfarin doses were compared between two 4-week periods, before and 18-21 weeks after initiating co-treatment with amiodarone. In addition, warfarin doses and international normalized ratio (INR) values were calculated week-by-week after the initiation of amiodarone. Results The initiation of amiodarone increased the mean INR from 2.6 to 3.1. The proportion of patients with a supratherapeutic INR over 3.0 and 4.0 increased from 12% to 37% and 0.9% to 5.5%, respectively. The subsequent mean decrease in warfarin dose was 24.6% (95% confidence interval [CI], 23.5, 25.6). The frequency of INR monitoring within 1 and 2 weeks after initiation of amiodarone was 67% and 90%. Conclusions Although warfarin doses in most patients were within the therapeutic range, more than one in three patients initiating co-treatment with amiodarone were exposed to a supratherapeutic anticoagulative effect within 3 weeks. In order to further avoid severe unnecessary bleeding, the initiation of amiodarone should be accompanied by closer INR monitoring, anticipating an average dose reduction of 25%.

Amiodaron in atrial fibrillation: post coronary artery bypass graft

BACKGROUND

Atrial fibrilation (AF) is the most common complication following heart surgeries; it often occurs in patients after coronary artery bypass graft (CABG). The purpose of this review is to categorize prophylaxes or treatment by administration of Amiodaron in patients with CABG.

DATA RESOURCES

We searched google scholar, pubmed, and Cochrane Library databases (the period 1970-2010) for articles on Amiodaron in CABG and cardiac surgery. A total of 1 561 articles were identified, and 30 articles met the criteria and were enrolled in this review.

RESULTS

Most studies supported Amiodarone for prophylaxi purpose in patients who were performed with CABG; few papers supported Amiodaron as a drug for treating CABG. The prophylaxis can decrease the incidence rate of AF in CABG, but if it uses as a treatment, the side effect of Amiodaron will decrease because all of the patients will not get Amiodarone. In the other hand use of Amiodarone as a treatment does not influence the length of hospital stay significantly but these kinds of study are so few.

CONCLUSION

No appropriate therapeutic method has been defined for AF. At present, the common way of treating AF following cardiac surgery is mainly based on prophylaxis in medical books and references.

Cancer metastasis and EGFR signaling is suppressed by amiodarone-induced versican V2

Extracellular matrix components play an active role in cancer progression and prognosis. Versican, a large extracellular matrix proteoglycan, can promote cancer metastasis through facilitating cell proliferation, adhesion, migration and angiogenesis. We had previously demonstrated that amiodarone caused ectopic overexpression of similar to versican b (s-vcanb), inhibited EGFR/GSK3β/Snail signaling, and enhanced Cdh5 at the heart field of zebrafish, indicating interference with epithelial-mesenchymal transition (EMT). Since S-vcanb is homologous to mammalian versican V2 isoform, we examined the effects of amiodarone on mammalian tumor proliferation, migration, invasion and metastasis in vitro and in vivo and on EMT signaling pathways. Monolayer wound assays and extracellular matrix transwell invasion assays showed reduced migration and invasion by 15 μM amiodarone treated B16OVA, JC, 4T-1, MDA-MB-231 and MCF-7 tumor cell lines. All cancer cell lines showed reduced metastatic capabilities in vivo after treatment with amiodarone in experimental animals. Western blots revealed that EMT-related transcription factors Snail and Twist were reduced and E-cadherin was enhanced in amiodarone treated cells through an EGFR/ERK/GSK3β-dependent pathway. Immunohistochemistry showed amiodarone lead to increased expression of versican V2 isoform concomitant with reduced versican V1. Our study illustrated the role of versican v2 in EMT modulation and cancer suppression by amiodarone treatment.

Amiodarone Rescue Therapy for Severe Decompensated Heart Failure Initially Unsuitable for β-Blockers

Background: β-Blocker therapy is now standard therapy for patients with stable heart failure; however, fluid-overloaded, New York Heart Association Class IV patients tolerate β-blockers poorly. Amiodarone, a drug with antiadrenergic effects, has been shown to improve survival for patients with heart rates of 90 beats per minute or greater.

Methods: We reviewed 26 patients with severe decompensated heart failure who were started on oral amiodarone for heart rate control. β-Blocker titration was attempted when patients became clinically stable.

Results: The mean age of the patients was 48.5±17.5 years, and 73% were male. Fifteen patients were New York Heart Association Class IV, and 11 were Class III. Of these, 23 (88%) were fluid-overloaded, and 11 (42%) were on inotropic agents when amiodarone was started. The mean ejection fraction was 16.1 ± 6%. The initial dose of amiodarone was 346 ± 120 mg/day. Twenty (77%) patients were successfully started on β-blockers. At follow-up prior to β-blockers, 20 (77%) patients improved by at least one New York Heart Association class. Heart rate decreased from a mean of 98 ± 15 to 78 ± 13 beats per minute (P < .0001). Echocardiograms were available in 12 patients, with ejection fractions increasing from 16.1 ± 8% to 26.8 ± 13% (P= .004).

Conclusions: Amiodarone may be an effective rescue therapy for patients with decompensated heart failure and serve as a bridge to subsequent β-blocker therapy.

Practical Management Guide for Clinicians Who Treat Patients with Amiodarone

Amiodarone, an iodinated benzofuran derivative with Class I, II, III, and IV antiarrhythmic properties, is the most commonly used antiarrhythmic drug used to treat supraventricular and ventricular arrhythmias. Appropriate use of this drug, with its severe and potentially life-threatening adverse effects, requires an essential understanding of its risk-benefit properties in order to ensure safety. The objective of this review is to afford clinicians who treat patients receiving amiodarone an appropriate management strategy for its safe use. The authors of this consensus management guide have thoroughly reviewed and evaluated the existing literature on amiodarone and apply this information, along with the collective experience of the authors, in its development. Provided are management guides on the intravenous and oral dosing of amiodarone, appropriate outpatient follow-up of patients taking the drug, its recognized adverse effects, and recommendations on when to consult specialists to help in patient management. All clinicians must be cognizant of the appropriate use, follow-up, and adverse reactions of amiodarone. The responsibility incurred by those treating such patients cannot be overemphasized.

Diagnostic Evaluation and Follow-Up of Patients with Atrial Fibrillation

In this article, a review of the diagnostic evaluation and outpatient follow-up of patients with atrial fibrillation is presented. After exploring details of symptoms, past medical history, quality of life, and physical exam findings, diagnostic tools are then discussed. Furthermore, important considerations after the initial diagnosis and treatment of patients with atrial fibrillation are discussed.

A Mechanistic Study on the Amiodarone-Induced Pulmonary Toxicity

Amiodarone- (AM-) induced pulmonary toxicity (AIPT) is still a matter of research and is poorly understood. In attempting to resolve this issue, we treated Sprague-Dawley rats with AM doses of 80 mg/kg/day/i.p. for one, two, three, and four weeks. The rats were weighed at days 7, 14, 21, and 28 and bronchoalveolar lavages (BAL) were obtained to determine total leukocyte count (TLC). For each group, lung weighing, histopathology, and homogenization were performed. Fresh homogenates were used for determination of ATP content, lipid peroxides, GSH, catalase, SOD, GPx, GR activities, NO, and hydroxyproline levels. The results showed a significant decrease in body weight and GSH depletion together with an increase in both lung weight and lung/body weight coefficient in the first week. Considerable increases in lung hydroxyproline level with some histopathological alterations were apparent. Treatment for two weeks produced a significant increase in BAL fluid, TLC, GR activity, and NO level in lung homogenate. The loss of cellular ATP and inhibition of most antioxidative protective enzymatic system appeared along with alteration in SOD activity following daily treatment for three weeks, while, in rats treated with AM for four weeks, more severe toxicity was apparent. Histopathological diagnosis was mostly granulomatous inflammation and interstitial pneumonitis in rats treated for three and four weeks, respectively. As shown, it is obvious that slow oedema formation is the only initiating factor of AIPT; all other mechanisms may occur as a consequence.

P450-Based Drug-Drug Interactions of Amiodarone and its Metabolites: Diversity of Inhibitory Mechanisms

In this study, IC50 shift and time-dependent inhibition (TDI) experiments were carried out to measure the ability of amiodarone (AMIO), and its circulating human metabolites, to reversibly and irreversibly inhibit CYP1A2, CYP2C9, CYP2D6, and CYP3A4 activities in human liver microsomes. The [I]u/Ki,u values were calculated and used to predict in vivo AMIO drug-drug interactions (DDIs) for pharmaceuticals metabolized by these four enzymes. Based on these values, the minor metabolite N,N-didesethylamiodarone (DDEA) is predicted to be the major cause of DDIs with xenobiotics primarily metabolized by CYP1A2, CYP2C9, or CYP3A4, while AMIO and its N-monodesethylamiodarone (MDEA) derivative are the most likely cause of interactions involving inhibition of CYP2D6 metabolism. AMIO drug interactions predicted from the reversible inhibition of the four P450 activities were found to be in good agreement with the magnitude of reported clinical DDIs with lidocaine, warfarin, metoprolol, and simvastatin. The TDI experiments showed DDEA to be a potent inactivator of CYP1A2 (KI = 0.46 μM, kinact = 0.030 minute(-1)), while MDEA was a moderate inactivator of both CYP2D6 (KI = 2.7 μM, kinact = 0.018 minute(-1)) and CYP3A4 (KI = 2.6 μM, kinact = 0.016 minute(-1)). For DDEA and MDEA, mechanism-based inactivation appears to occur through formation of a metabolic intermediate complex. Additional metabolic studies strongly suggest that CYP3A4 is the primary microsomal enzyme involved in the metabolism of AMIO to both MDEA and DDEA. In summary, these studies demonstrate both the diversity of inhibitory mechanisms with AMIO and the need to consider metabolites as the culprit in inhibitory P450-based DDIs.