Adverse effects of amiodarone

Association between amiodarone use and risk of cataract: a population-based active-comparator study

BACKGROUND

Despite previous concerns about ocular side effects related to amiodarone, the relationship between amiodarone and cataract remains uncertain. Therefore, this study aimed to assess the potential association between amiodarone use and the subsequent risk of cataract, taking into account potential confounders.

METHODS

This population-based, active comparator-controlled cohort study utilized the data from the Taiwan National Health Insurance program and involved adults over 40 years old between 2001 and 2013. We analyzed 12 055 new amiodarone users and contrasted them with a propafenone user cohort. The primary outcome was the incidence of cataract. Inverse-probability treatment-weighting (IPTW) was further used to eliminate the potential confounding effects, and Cox proportional-hazard regression analyses were performed to calculate the risk of cataract. Serial subgroup analyses were also performed.

RESULTS

In the main analysis, amiodarone users did not exhibit a significant causal relationship in both full cohort [adjusted hazard ratio (aHR): 0.994, 95% confidence interval (CI): 0.913-1.082] and IPTW cohort (IPTW-aHR 0.977, 95% CI: 0.900-1.060). Furthermore, it is important to highlight a significantly reduced risk of cataract among patients with heart failure (IPTW-aHR 0.708, 95% CI: 0.554-0.905) and during the 2-year follow-up period (IPTW-aHR 0.889, 95% CI: 0.794-0.996), implying potential advantages linked to the use of amiodarone.

CONCLUSIONS

The study found no increased risk of cataract with amiodarone, one of the most frequently used antiarrhythmic medications, compared to the use of propafenone. Future research is recommended to explore potential mechanisms and their implications for clinical practice.

Integrating distribution kinetics and toxicodynamics to assess repeat dose neurotoxicity in vitro using human BrainSpheres: a case study on amiodarone

For ethical, economical, and scientific reasons, animal experimentation, used to evaluate the potential neurotoxicity of chemicals before their release in the market, needs to be replaced by new approach methodologies. To illustrate the use of new approach methodologies, the human induced pluripotent stem cell-derived 3D model BrainSpheres was acutely (48 h) or repeatedly (7 days) exposed to amiodarone (0.625-15 µM), a lipophilic antiarrhythmic drug reported to have deleterious effects on the nervous system. Neurotoxicity was assessed using transcriptomics, the immunohistochemistry of cell type-specific markers, and real-time reverse transcription-polymerase chain reaction for various genes involved in the lipid metabolism. By integrating distribution kinetics modeling with neurotoxicity readouts, we show that the observed time- and concentration-dependent increase in the neurotoxic effects of amiodarone is driven by the cellular accumulation of amiodarone after repeated dosing. The development of a compartmental in vitro distribution kinetics model allowed us to predict the change in cell-associated concentrations in BrainSpheres with time and for different exposure scenarios. The results suggest that human cells are intrinsically more sensitive to amiodarone than rodent cells. Amiodarone-induced regulation of lipid metabolism genes was observed in brain cells for the first time. Astrocytes appeared to be the most sensitive human brain cell type in vitro. In conclusion, assessing readouts at different molecular levels after the repeat dosing of human induced pluripotent stem cell-derived BrainSpheres in combination with the compartmental modeling of in vitro kinetics provides a mechanistic means to assess neurotoxicity pathways and refine chemical safety assessment for humans.

Amiodarone-Induced Liver Attenuation on CT Scan: Alarming Signal for Toxicity and Prompt Discontinuation

Amiodarone, a class III antiarrhythmic drug, is commonly used for the management of life-threatening ventricular arrhythmias, atrial fibrillation, and other refractory supra-ventricular arrhythmias. Factors like a large volume of distribution, lipophilic property, deposition in tissues in large amounts, etc. have led to the development of amiodarone-induced multisystem adverse events. We report a case of amiodarone-induced hepatic attenuation on computed tomography (CT) of the abdomen in an elderly female patient. Amiodarone with a composition of 40% iodine by weight deposits in the liver, leading to characteristically increased radiodensity reported as increased attenuation on CT scan. Surprisingly, the severity and extent of hepatic attenuation on CT scans do not necessarily correlate with the total exposure to amiodarone over time. Individual factors may influence the liver's response to the drug, leading to varying degrees of hepatic changes. To minimize the risk of adverse events associated with amiodarone, clinicians should carefully adjust the dosage to the lowest effective level and regularly monitor liver function tests in patients. This proactive approach enables early detection of liver dysfunction and facilitates timely adjustments or discontinuation of amiodarone, thereby reducing potential harm.

An Overview of Systematic Reviews on the Effectiveness of Wenxin Keli in the Treatment of Atrial Fibrillation

Background

Atrial fibrillation is one of the most common cardiac arrhythmias. Wenxin Keli (WXKL) is a Chinese herbal extract widely used in China to treat patients with atrial fibrillation. This study aimed to outline and summarize the current evidence of systematic reviews (SRs)/meta-analyses (MAs) investigating the clinical efficacy of WXKL in atrial fibrillation.

Methods

From inception to December 2021, 6 electronic databases in English and Chinese were searched for potential SRs/MAs. The GRADE (Grading of Recommendations Assessment, Development, and Evaluation), PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) checklist, and AMSTAR-2 (Assessing the Methodological Quality of Systematic Reviews-2) were used to evaluate the quality of the evidence, reporting, and methodology of SRs/MAs regarding WXKL for the treatment of atrial fibrillation.

Results

A total of 8 SRs/MAs were included in the present study. The results of AMSTAR-2 and PRISMA were unsatisfactory for the main insufficiency founded in registration and protocol, search strategy, excluded study statement, evidence certainty assessment, and funding and conflict of interest information. All the included SRs/MAs were assessed as very low in methodological quality. Moreover, 23 outcomes were evaluated by GRADE for the certainty of evidence, and 2 outcomes were assessed as moderate, while 15 were low and 6 were very low. Risk of bias and publication bias contributed to the downgrading.

Conclusion

WXKL may be clinically efficacious and safe for the treatment of atrial fibrillation. This finding, however, should be regarded with caution because of the low level of evidence and methodological qualities of the involved SRs/MAs. More standardized, rigorous, and comprehensive SRs/MAs and randomized control trials are needed to provide strong evidence to reach more convincing conclusions.

Development and Validation of a Novel HPLC Method to Analyse Metabolic Reaction Products Catalysed by the CYP3A2 Isoform: In Vitro Inhibition of CYP3A2 Enzyme Activity by Aspirin (Drugs Often Used Together in COVID-19 Treatment)

Aspirin (also known as acetylsalicylic acid) is a drug intended to treat fever, pain, or inflammation. Treatment of moderate to severe cases of COVID-19 using aspirin along with dexamethasone has gained major attention globally in recent times. Thus, the purpose of this study was to use High-Performance Liquid Chromatography (HPLC) to evaluate the in vitro inhibition of CYP3A2 enzyme activity using aspirin in rat liver microsomes (RLMs). In this study, an efficient and sensitive HPLC method was developed using a reversed phase C18 column (X Bridge 4.6 mm × 150 mm, 3.5 µm) at 243 nm using acetonitrile and water (70:30 v/v). The linearity (r2 > 0.999), precision (<15%), accuracy and recovery (80–120%), limit of detection (5.60 µM and 0.06 µM), limit of quantification (16.98 µM and 0.19 µM), and stability of the newly developed method were validated for dexamethasone and 6β-hydroxydexamethasone, respectively, following International Conference on Harmonization (ICH) guidelines. This method was applied in vitro to measure CYP3A2 activity. The results showed that aspirin competitively inhibits 6β-hydroxylation (CYP3A2 activity) with an inhibition constant (Ki) = 95.46 µM and the concentration of the inhibitor causing 50% inhibition of original enzyme activity (IC50) = 190.92 µM. This indicated that there is a minimal risk of toxicity when dexamethasone and aspirin are co-administrated and a very low risk of toxicity and drug interaction with drugs that are a substrate for CYP3A2 in healthcare settings.

Sotalol versus amiodarone for postoperative junctional tachycardia after congenital heart surgery

BACKGROUND

Junctional ectopic tachycardia (JET) is a common arrhythmia after congenital heart disease surgery. There is variability in the choice of antiarrhythmic therapy, with amiodarone used commonly. Intravenous (IV) sotalol is a newly available agent that may be useful for JET.

OBJECTIVE

The purpose of this study was to evaluate the safety and efficacy of IV sotalol for postoperative JET and compare outcomes with IV amiodarone.

METHODS

This is a retrospective single-center study of all patients who received IV sotalol or IV amiodarone for postoperative JET at Texas Children's Hospital from December 15, 2015, to December 15, 2020. Data included antiarrhythmic efficacy, hemodynamics, and adverse effects. Successful JET control was defined as a decrease in JET rate to <170 beats/min (or decrease by >20%), or conversion to sinus rhythm, with persistent control over 24 hours without requiring alternative antiarrhythmics or mechanical support.

RESULTS

A total of 32 patients (median age 71 days; interquartile range 17-221 days) received IV amiodarone (n = 20 [62%]) or IV sotalol (n = 12 [38%]) for postoperative JET. Amiodarone was successful in treating JET in 75% of cases; sotalol was successful in 83%. The JET rate decreased faster over the first 90 minutes after a sotalol bolus (25 beats/min per hour) than after an amiodarone bolus (8 beats/min per hour) (P < .01); no heart rate difference was seen after 24 hours. Amiodarone infusion was discontinued early because of hypotension/bradycardia in 2 patients; this was not required in any patients receiving sotalol.

CONCLUSION

For children with postoperative JET, both IV sotalol and amiodarone are safe and efficacious. IV sotalol may lead to a faster improvement in heart rate.

Current Drug Treatment Strategies for Atrial Fibrillation and TASK-1 Inhibition as an Emerging Novel Therapy Option

Atrial fibrillation (AF) is the most common sustained arrhythmia with a prevalence of up to 4% and an upwards trend due to demographic changes. It is associated with an increase in mortality and stroke incidences. While stroke risk can be significantly reduced through anticoagulant therapy, adequate treatment of other AF related symptoms remains an unmet medical need in many cases. Two main treatment strategies are available: rate control that modulates ventricular heart rate and prevents tachymyopathy as well as rhythm control that aims to restore and sustain sinus rhythm. Rate control can be achieved through drugs or ablation of the atrioventricular node, rendering the patient pacemaker-dependent. For rhythm control electrical cardioversion and pharmacological cardioversion can be used. While electrical cardioversion requires fasting and sedation of the patient, antiarrhythmic drugs have other limitations. Most antiarrhythmic drugs carry a risk for pro-arrhythmic effects and are contraindicated in patients with structural heart diseases. Furthermore, catheter ablation of pulmonary veins can be performed with its risk of intraprocedural complications and varying success. In recent years TASK-1 has been introduced as a new target for AF therapy. Upregulation of TASK-1 in AF patients contributes to prolongation of the action potential duration. In a porcine model of AF, TASK-1 inhibition by gene therapy or pharmacological compounds induced cardioversion to sinus rhythm. The DOxapram Conversion TO Sinus rhythm (DOCTOS)-Trial will reveal whether doxapram, a potent TASK-1 inhibitor, can be used for acute cardioversion of persistent and paroxysmal AF in patients, potentially leading to a new treatment option for AF.

Amiodarone-induced neuromyopathy in a geriatric patient

Amiodarone is an antiarrhythmic medication with many side effects. Neuromyopathy is a rare adverse effect. We present an 87-year-old woman with bilateral leg pain and weakness in the context of amiodarone. She was admitted to the Acute Geriatric Unit in Calgary, Alberta, Canada. On examination, hip flexor and extensor strength were 2/5 bilaterally while knee flexor and extensor strength were 4/5 and 3/5, respectively. Creatine kinase and C-reactive protein levels were normal. MRI of the lumbar spine showed mild central canal stenosis. Electromyography and nerve conduction testing showed a severe axonal length-dependent polyneuropathy of the left lower extremity. There was evidence of myopathic changes to the left iliopsoas muscle. Overall, a neuromyopathic process affecting the lower extremities was supported. After discontinuation of amiodarone, mobility and function significantly improved. Although a rare complication of amiodarone, neuromyopathy should be considered in patients with compatible symptomatology.

Amiodarone treatment in atrial fibrillation and the risk of incident cancers: A nationwide observational study

BACKGROUND

In observational studies, case reports, and animal studies, amiodarone has been associated with incident cancer.

OBJECTIVE

The purpose of this study was to examine whether a dose-response relationship between amiodarone use and the risk of cancer could be ascertained in a large nationwide study cohort.

METHODS

Using nationwide registers, we included all Danish patients with atrial fibrillation (AF) treated with amiodarone from 1996 to 2014. Exposure was defined both by categories and as a continuous variable of the cumulative defined daily doses (cDDDs) of amiodarone. The associations between amiodarone cDDD and incident cancer, as well as organ-specific types of cancer (skin, liver, lung), were estimated using multivariable Cox regression models and reported as hazard ratios (HR) with 95% confidence intervals (CI) and using cubic restricted spline plots.

RESULTS

We included 18,503 patients with a median follow-up time of 8.1 years (interquartile range [IQR] 4.3-12.4). Median age was 70 years (IQR 63-77). A total of 2974 individuals developed cancer during follow-up. We found no association between increasing amiodarone exposure (cDDD 181-400 and cDDD >400) and the hazard of incident cancer (HR 0.95; 95% CI 0.87-1.04; and HR 1.01; 95% CI 0.92-1.10) with reference to patients with cDDD <181. Similar results were found when investigating specific cancer types (skin, liver, and lung) as well as cDDD as a continuous variable.

CONCLUSION

In a large nationwide cohort of AF patients treated with amiodarone, we found no evidence of a dose-response relationship between cumulative dose of amiodarone and incident cancer risk.

Improvement in Dyssynchrony with Pharmacological Ablation of Right-Sided Accessory Pathway-Induced Cardiomyopathy in Infants

Right-sided accessary pathways in patients with Wolff-Parkinson-White (WPW) syndrome may cause cardiac dyssynchrony and dilated cardiomyopathy, with a characteristic septal shape, irrespective of any supraventricular tachycardia episodes. We report on two infants (13 and 5 months), whose right-sided accessary pathway-induced dilated cardiomyopathy was successfully treated by flecainide for the first time. After the flecainide administration, an abnormal aneurysmal dilation of the basal interventricular septum was almost restored to normal, and the decreased ejection fraction recovered. Flecainide use may be an important therapeutic option for this entity to avoid catheter ablation during infancy.

Cardiovascular Collapse with Intravenous Amiodarone in Children: A Multi-Center Retrospective Cohort Study

OBJECTIVE

To determine the incidence of cardiovascular collapse in children receiving intravenous (IV) amiodarone and to identify the population at risk.

DESIGN

A multicenter study of patients ≤ 18 years of age who received intravenous amiodarone between January 2005 and December 2015. A retrospective analysis was performed to identify patients who developed cardiovascular collapse (bradycardia and/or hypotension).

RESULTS

Of 456 patients who received amiodarone, cardiovascular collapse occurred in 47 patients (10%). Patient risk factors for collapse in a univariate analysis were as follows: age < 3 months (p = 0.04), depressed cardiac function (p < 0.001), blood pressure below 3rd percentile (p < 0.001), high lactate at baseline (p < 0.001). Administration risk factors included bolus administration (p = 0.04), and bolus administration over ≤ 20 min (p = 0.04). In multivariate analysis, age, baseline blood pressure less than 3rd percentile, and rapid bolus delivery were independent risk factors for cardiovascular collapse in the study group. The mortality rate was significantly higher in the collapse group (28% versus 8%).

CONCLUSION

We found an association between IV amiodarone administration and the risk of developing cardiovascular collapse in a significant subset of children. Extreme caution and careful hemodynamic monitoring is recommended when using IV amiodarone in this population, especially in young infants, hemodynamically compromised patients, and in patients receiving rapid amiodarone bolus administration.

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.

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.

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.

Cardiac ion channels and mechanisms for protection against atrial fibrillation

Atrial fibrillation (AF) is recognised as the most common sustained cardiac arrhythmia in clinical practice. Ongoing drug development is aiming at obtaining atrial specific effects in order to prevent pro-arrhythmic, devastating ventricular effects. In principle, this is possible due to a different ion channel composition in the atria and ventricles. The present text will review the aetiology of arrhythmias with focus on AF and include a description of cardiac ion channels. Channels that constitute potentially atria-selective targets will be described in details. Specific focus is addressed to the recent discovery that Ca(2+)-activated small conductance K(+) channels (SK channels) are important for the repolarisation of atrial action potentials. Finally, an overview of current pharmacological treatment of AF is included.

Rapid stimulating effect of the antiarrhythmic agent amiodarone on absorption of organic anion compounds

In a clinical setting, changes in pharmacokinetics due to drug-drug interactions can often directly affect the therapeutic safety and efficacy of drugs. Recently, interest has been shown in drug-drug interactions in the intestine. It is now recognized that changes in the functions of drug transporters substantially influence the absorption of administered drugs from the intestine. Amiodarone (AMD) is a potent drug used in the treatment of serious supraventricular and ventricular tachyarrhythmias. Despite its potent pharmacological effects, its wide clinical use is precluded by drug-drug interactions. In this study, we characterized the transporter function between AMD and various compounds in human intestinal model Caco-2 cells. AMD significantly and rapidly increased the uptake of [(3)H]estrone-3-sulfate (E-3-S) for 5 min. The apical-to-basal transport of [(3)H]E-3-S was significantly increased by AMD. The AMD-stimulated [(3)H]E-3-S uptake was inhibited by organic anion transporting polypeptide (OATP) substrates. Caco-2 cells treated with AMD showed increased OATP2B1 expression on the cell surface. AMD also increased the absorption of sulfobromophthalein (BSP), which is a typical organic anion compound, and the expression level of Oatp2b1 at the membrane in in vivo experiments. The results indicate that AMD induces OATP2B1/Oatp2b1 expression at the membrane in the intestine and enhances absorption of organic anion compounds.

Comparison of effectiveness and safety of ranolazine versus amiodarone for preventing atrial fibrillation after coronary artery bypass grafting

Atrial fibrillation (AF) is common after coronary artery bypass grafting (CABG) and increases the morbidity and cost. Amiodarone reduces AF after CABG. Ranolazine, an antianginal agent, also prolongs atrial refractoriness and inhibits after depolarizations and triggered activity; effects that could decrease AF after CABG. The present study compared amiodarone versus ranolazine for the prevention of AF after CABG. A retrospective cohort study of patients undergoing CABG at Aspirus Hospital from June 2008 to April 2010. The patients received either amiodarone (400 mg preoperatively followed by 200 mg twice daily for 10 to 14 days) or ranolazine (1,500 mg preoperatively followed by 1,000 mg twice daily for 10 to 14 days). The primary end point was any identified AF after CABG. A total of 393 consecutive patients undergoing CABG (mean age 65 ± 10 years, 72% men) received either amiodarone (n = 211 [53.7%]) or ranolazine (n = 182 [46.3%]). AF occurred in 26.5% of the amiodarone-treated patients compared to 17.5% of the ranolazine-treated patient (p = 0.035). The univariate predictors of AF included amiodarone use, age, chronic lung disease, and congestive heart failure. The multivariate predictors of AF included amiodarone use (odds ratio 1.7, 95% confidence interval 1.01 to 2.91, p = 0.045 vs ranolazine), age (odds ratio 2.2 per 10 years, 95% confidence interval 1.63 to 2.95, p <0.001), and chronic lung disease (odds ratio 1.86, 95% confidence interval 1.00 to 3.43, p = 0.049). No difference was found in the risk of adverse events between the 2 therapies. In conclusion, ranolazine was independently associated with a significant reduction of AF compared to amiodarone after CABG, with no difference in the incidence of adverse events. Randomized studies should be conducted to confirm these results.

Efflux transport of N-monodesethylamiodarone by the human intestinal cell-line Caco-2 cells

Amiodarone (AMD) is a benzofurane derivative with class III antiarrhythmic activity that is effective in controlling intractable cardiac arrhythmias. One of the most common and serious drug interactions in clinical practice is the interaction between digoxin and an antiarrhythmic agent. It has been reported that AMD and N-monodesethylamiodarone (DEA), the active metabolite of AMD, inhibit the P-glycoprotein (P-gp/MDR1)-mediated digoxin transport. However, the intestinal transport processes of AMD and DEA have not been fully revealed. In this study, we focused on the intestinal transport mechanism of DEA and characterized the intestinal transport of DEA using Caco-2 cells. Basal-to-apical transport of DEA by Caco-2 cells was greater than apical-to-basal transport. The relationship between concentration and basal-to-apical flux rate appeared to approach saturation. The uptake of DEA by Caco-2 cells was increased in the presence of typical ATP-depletion compounds and thyroid hormones. On the other hand, substrates for P-gp, multidrug resistance-associated proteins (MRPs/ABCCs) and breast cancer resistance protein (BCRP/ABCG2) had no effect on the efflux of DEA. These results suggest that an ATP-binding cassette (ABC) transporter, which is different from P-gp, MRPs and BCRP, mediates the efflux of DEA across the apical membrane in Caco-2 cells and that thyroid hormone inhibits this transporter.

A practical guide for clinicians who treat patients with amiodarone: 2007

Amiodarone is commonly used to treat supraventricular and ventricular arrhythmias in various inpatient and outpatient settings. Over- and under-use of amiodarone is common, and data regarding patterns of use are sparse and largely anecdotal. Because of adverse drug reactions, proper use is essential to deriving optimal benefits from the drug with the least risk. This guide updates an earlier version published in 2000, reviews indications for use of amiodarone and recommends strategies to minimize adverse effects. The recommendations included herein are based on the best available data and the collective experience of the member of the writing committee.

Flow injection chemiluminescent determination of amiodarone in pharmaceutical preparations using photogenerated tris(2,2′-bipyridyl)ruthenium(III)

A flow injection configuration was developed and evaluated for the chemiluminescent determination of amiodarone. The method is based on the reaction of the drug with tris(2,2'-bipyridyl)ruthenium(III), which was generated through the on-line photo-oxidation of tris(2,2'-bipyridyl)ruthenium(II) with peroxydisulfate. Under the optimum experimental conditions, a linear calibration graph was obtained over the range 3.0-60.0 microg ml(-1) with a detection limit of 0.28 microg ml(-1). The proposed method allows 120 injections h(-1) with excellent repeatability and precision (R.S.D. less than 0.5% and 2.8%, respectively) and a reagent consumption of only 0.37 micromol (0.27 mg) of Ru(bpy)(3)Cl(2) x 6H(2)O per determination. The method was successfully applied to the determination of amiodarone in commercial pharmaceutical formulations.

Antiarrhythmic drug therapy for atrial fibrillation: are the guidelines guiding clinical practice?

The AFFIRM study showed no clear survival advantage for a rhythm versus rate control strategy in patients with atrial fibrillation (AF). However, rhythm control with antiarrhythmic drugs (AADs) is appropriate in a large number of patients with AF. The American College of Cardiology/ American Heart Association/European Society of Cardiology AF management guidelines include a safety-based algorithm for selection of AAD therapy. Class 1C agents are recommended as first-line therapy in patients without or with minimal structural heart disease. However, market research and clinical study data indicate a growing use of class III agents (mainly amiodarone) despite long-term safety and tolerability concerns, suggesting that clinical practice does not adhere to current guidelines.

Antiarrhythmic drug therapy of atrial fibrillation

In the post-AFFIRM era, treatment of AF has become the treatment of symptoms. In some patients, this will be simple rate control, but there remain a significant cohort of patients in whom rate control alone does not give acceptable symptom relief. In this group, antiarrhythmic therapy still has a role, and the AFFIRM trial indicates that this therapeutic strategy is without significant deleterious effect on mortality. The choice of antiarrhythmic agent must be individualized according to underlying cardiac pathologies and comorbidities, however. Most recently, the introduction of dofetilide has widened the therapeutic options in patients with severe heart disease, and the Canadian Trial of Atrial Fibrillation indicated the superior efficacy of amiodarone at low doses. The release/ development of newer Class III antiarrhythmic agents may offer hope for the benefits of amiodarone without the serious adverse effects with long-term therapy.

Validated Spectrophotometric Methods for the Determination of Amiodarone Hydrochloride in Commercial Dosage Forms Using p-Chloranilic Acid and 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone

Two simple, sensitive and economical spectrophotometric methods have been developed for the determination of amiodarone hydrochloride in pure form and commercial dosage form. These methods (A and B) are based on the reaction of amiodarone base as n-electron donor with p-chloranilic acid and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as pi-acceptors to give highly colored complex species which absorb maximally at 535 and 570 nm, respectively. Beer's law is obeyed in the concentration ranges 10.0 - 360.0 and 2.0 - 65.0 microg ml(-1) for methods A and B, respectively. Application of the proposed methods to commercial pharmaceutical tablets are presented.

Clinical relevance and management of drug-related QT interval prolongation

Much attention recently has focused on drugs that prolong the QT interval, potentially leading to fatal cardiac dysrhythmias (e.g., torsade de pointes). We provide a detailed review of the published evidence that supports or does not support an association between drugs and their risk of QT prolongation. The mechanism of drug-induced QT prolongation is reviewed briefly, followed by an extensive evaluation of drugs associated with QT prolongation, torsade de pointes, or both. Drugs associated with QT prolongation are identified as having definite, probable, or proposed associations. The role of the clinician in the prevention and management of QT prolongation, drug-drug interactions that may occur with agents known to affect the QT interval, and the impact of this adverse effect on the regulatory process are addressed.

Amiodarone versus placebo and class Ic drugs for cardioversion of recent-onset atrial fibrillation: a meta-analysis

OBJECTIVES

This meta-analysis compared amiodarone with placebo and class Ic drugs for the cardioversion of recent-onset atrial fibrillation (AF), defined as lasting less than seven days.

BACKGROUND

Despite the lack of trials that support its efficacy convincingly, amiodarone is widely used for conversion of recent-onset AF.

METHODS

We searched Medline and EMBASE databases, as well as the Cochrane Controlled Trials Register for randomized trials on recent-onset AF comparing amiodarone to placebo or class Ic drugs. Data were combined according to a fixed effect model. The primary end point was the rate of conversion at 24 h. To study time-dependency of the drugs, efficacy at 1 to 2 h, 3 to 5 h, 6 to 8 h, and at 24 h was analyzed.

RESULTS

We found six studies randomizing amiodarone versus placebo (595 patients) and seven studies versus class Ic drugs (579 patients). There was no significant difference between amiodarone and placebo at 1 to 2 h, but significant efficacy was found after 6 to 8 h (relative risk [RR] 1.23, p = 0.022) and at 24 h (RR 1.44, p < 0.001). Efficacy with amiodarone was inferior to class Ic drugs for up to 8 h (RR 0.67, p < 0.001) but no difference was seen at 24 h (RR 0.95, p = 0.50). There were no major adverse effects.

CONCLUSIONS

Amiodarone is superior to placebo for cardioversion of AF, and even though the onset of conversion is delayed, its efficacy is similar at 24 h compared with class Ic drugs. These results favor amiodarone as a reasonable alternative for patients with recent AF in whom class Ic and other, more rapidly acting antiarrhythmic drugs cannot be used.

Low dose amiodarone and sotalol in the treatment of recurrent, symptomatic atrial fibrillation: a comparative, placebo controlled study

OBJECTIVE

To assess and compare the safety and efficacy of amiodarone and sotalol in the treatment of patients with recurrent symptomatic atrial fibrillation.

DESIGN

Prospective, randomised, single blind, placebo controlled study.

SETTING

Tertiary cardiac referral centre.

PATIENTS

186 consecutive patients (97 men, 89 women; mean (SD) age, 63 (10) years) with recurrent, symptomatic atrial fibrillation.

INTERVENTIONS

65 patients were randomised to amiodarone, 61 to sotalol, and 60 to placebo. Patients receiving amiodarone were maintained at a dose of 200 mg/day after a 30 day loading phase. The sotalol dose was 160-480 mg daily, as tolerated.

MAIN OUTCOME MEASURES

Recurrence of atrial fibrillation or side effects.

RESULTS

In the amiodarone group, 31 of the 65 patients developed atrial fibrillation after an average of six months, while 15 (11 in sinus rhythm and four in atrial fibrillation) experienced significant side effects after an average of 16 months. In the sotalol group, relapse to atrial fibrillation occurred in 47 of the 61 patients after an average of eight months; three experienced side effects during the titration phase. In the placebo group, 53 of the 60 patients developed atrial fibrillation after an average of four months (p < 0.001 for amiodarone and sotalol v placebo; p < 0.001 for amiodarone v sotalol).

CONCLUSIONS

Both amiodarone and sotalol can be used for the maintenance of normal sinus rhythm in patients with symptomatic atrial fibrillation. Amiodarone is more effective but causes more side effects.

The Management of Atrial Fibrillation in the ICU

Atrial tachyarrhythmias are the most frequent arrhythmias occurring in ICU patients, being particularly common in patients with cardiovascular and respiratory failure. Unlike ambulatory patients in whom atrial fibrillation/flutter (AF) is likely to be short lived, in the critically ill these arrhythmias are unlikely to resolve until the underlying disease process has improved. Urgent cardioversion is indicated for hemodynamic instability. Treatment in hemodynamically stable patients includes correction of treatable precipitating factors, control of the ventricular response rate, conversion to sinus rhythm, and prophylaxis against thromboembolic events in those patients who remain in AF. Diltiazem is the preferred agent for rate control, while procainamide and amiodarone are generally considered to be the antiarrhythmic agents of choice.

Amiodarone as a first-choice drug for restoring sinus rhythm in patients with atrial fibrillation: a randomized, controlled study

STUDY OBJECTIVES

To investigate the efficacy and safety of amiodarone administered as the drug of first choice in the conversion of atrial fibrillation, regardless of its duration.

DESIGN

: Prospective, randomized, controlled clinical study.

SETTING

: Tertiary cardiac referral center.

PATIENTS

Two-hundred eight consecutive patients (102 men; mean [+/- SD] age, 65 +/- 10 years) with atrial fibrillation.

INTERVENTIONS

One-hundred eight patients received amiodarone, and 100 patients received placebo treatment. Patients randomized to amiodarone received 300 mg IV for 1 h, and then 20 mg/kg for 24 h. They were also given 600 mg/d orally, divided into three doses, for 1 week, and thereafter 400 mg/d for 3 weeks. Patients randomized to placebo treatment received an identical amount of saline solution IV over 24 h, and oral placebo treatment for 1 month.

MEASUREMENTS AND RESULTS

Baseline clinical characteristics were similar in the two groups. Conversion to sinus rhythm was achieved in 87 of 108 patients (80.05%) who received amiodarone, and in 40 of 100 patients (40%) in the placebo group (p < 0.0001). Statistical analysis showed that the duration of the arrhythmia and the size of the left atrium affected both the likelihood of conversion to sinus rhythm and the time to conversion in both groups. No side effects requiring discontinuation of treatment were observed in either group.

CONCLUSIONS

Amiodarone appears to be safe and effective in the termination of atrial fibrillation. However, extreme cases with a large left atrium and long-lasting arrhythmia need long-term therapy.

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

AIMS

To predict the drug interactions of amiodarone and other drugs, the inhibitory effects and inactivation potential for human cytochrome P450 (CYP) enzymes by amiodarone and its N-dealkylated metabolite, desethylamiodarone were examined.

METHODS

The inhibition or inactivation potency of amiodarone and desethylamiodarone for human CYP activities were investigated using microsomes from B-lymphoblastoid cell lines expressing CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4. The in vivo drug interactions of amiodarone and desethylamiodarone were predicted in vitro using the 1+Iu/Ki values.

RESULTS

Amiodarone weakly inhibited CYP2C9, CYP2D6, and CYP3A4-mediated activities with Ki values of 45.1-271.6 microm. Desethylamiodarone competitively inhibited the catalytic activities of CYP2D6 (Ki=4.5 microm ) and noncompetitively inhibited CYP2A6 (Ki=13.5 microm ), CYP2B6 (Ki=5.4 microm ), and CYP3A4 (Ki=12.1 microm ). The catalytic activities of CYP1A1 (Ki=1.5 microm, alpha=5.7), CYP1A2 (Ki=18.8 microm, alpha=2.6), CYP2C9 (Ki=2.3 microm, alpha=5.9), and CYP2C19 (Ki=15.7 microm, alpha=4.5) were inhibited by desethylamiodarone with mixed type. The 1+Iu/Ki values of desethylamiodarone were higher than those of amiodarone. Amiodarone inactivated CYP3A4, while desethylamiodarone inactivated CYP1A1, CYP1A2, CYP2B6, and CYP2D6.

CONCLUSIONS

The interactions between amiodarone and other drugs might occur via the inhibition of CYP activities by its N-dealkylated metabolite, desethylamiodarone, rather than by amiodarone itself. In addition, the inactivation of CYPs by desethylamiodarone as well as by amiodarone would also contribute to the drug interactions.

Review of common adverse effects of selected antiarrhythmic drugs

The management of cardiac arrhythmias has changed dramatically over the past several years. New drugs and devices are now available to treat various arrhythmias. Many new agents have been developed that rely on different electrophysiologic mechanisms to elicit their effect on the heart rhythm. Though often effective, these drugs also pose a risk because all of them have a variety of potential adverse effects associated with their use. Many of these adverse reactions are common to all antiarrhythmic drugs, whereas others are unique to particular agents. This review discusses the notable adverse effects of selected antiarrhythmic drugs.

Interactions between implantable cardioverter-defibrillators and class III agents

Although implantable cardioverter-defibrillators (ICDs) can successfully terminate ventricular arrhythmias, antiarrhythmic drugs are often required to prevent recurrent events. Class III antiarrhythmic agents have emerged as the safest, most effective, and widely used agents in the 40-70% of ICD patients who require concomitant antiarrhythmic medication. Antiarrhythmic agents can influence the effectiveness of ICDs to terminate arrhythmias through their effect on defibrillation threshold. All class III agents share the ability to prolong ventricular refractoriness and those with "pure" class III activity consistently decrease defibrillation threshold in the normal canine heart model. Sotalol, amiodarone, and bretylium all have other Vaughan Williams class actions that influence their respective effects on defibrillation threshold. Sotalol has been associated with a decrease in defibrillation threshold in both animal and in clinical studies, whereas amiodarone has been associated with variable effects in animal models and an increase in defibrillation threshold in clinical studies. Additionally, antiarrhythmic agents may prolong ventricular tachycardia (VT) cycle length, which may affect the ability to pace terminate or cardiovert VT. Amiodarone has a moderate slowing effect on the VT cycle length. Finally, class III drugs also have proarrhythmic potential that may affect the defibrillator's function. Sotalol can be associated with dose-related torsade de pointes, whereas amiodarone may slow the VT cycle length below the tachycardia detection rate cutoff. In conclusion, class III pharmacotherapy can be safely administered in conjunction with ICD therapy as long as the interaction between these therapeutic modalities is appreciated.