Adverse effects of amiodarone. Pathogenesis, incidence and management

Development, validation and long-term evaluation of a liquid chromatography-tandem mass spectrometry method for simultaneous quantification of amiodarone, desethylamiodarone and mexiletine in human plasma and serum

Amiodarone and mexiletine are used for ventricular arrhythmias, for which a combination therapy of both anti-arrhythmic drugs (AADs) is not uncommon. Therapeutic drug monitoring (TDM) can be beneficial for clinical guidance of therapy, especially to correctly identify adverse events. Desethylamiodarone, the active metabolite of amiodarone, accumulates over time and is associated with serious adverse events. Therefore, simultaneous TDM for amiodarone, desethylamiodarone and mexiletine is advantageous in clinical practice. The presented LC-MS/MS method was validated for selectivity, matrix effect, linearity, accuracy, precision, carry-over and stability. The method was continuously evaluated during eight months of clinical use. The method was shown to be linear within the measured range of 0.1 to 10 mg/L for each component. The matrix effect was considered negligible. No interfering responses were found for amiodarone, desethylamiodarone and the isotopic-labeled internal standards. A constant and reproducible within-run contribution of 45.3 %, originating from the system, was identified for mexiletine. The systemic contribution to the peak area of the lowest quantifiable concentration of mexiletine affected the selectivity and carry-over effect measurements. Multiple measurements showed that regression adjusted concentrations were accurate and reproducible, indicating calibration correction was applicable. Sample stability was found to be within limits for all storage conditions and freeze-thaw cycles. Furthermore, long-term method evaluation with external controls resulted in stable measurements with a percentage coefficient of variance between 1.3 % and 6.3 %. The presented practical and reliable method is applicable for clinical TDM and will allow clinical practitioners to guide drug therapy of amiodarone and mexiletine.

Potential therapeutic approaches for modulating expression and accumulation of defective lamin A in laminopathies and age-related diseases

Scientific understanding of the genetic components of aging has increased in recent years, with several genes being identified as playing roles in the aging process and, potentially, longevity. In particular, genes encoding components of the nuclear lamina in eukaryotes have been increasingly well characterized, owing in part to their clinical significance in age-related diseases. This review focuses on one such gene, which encodes lamin A, a key component of the nuclear lamina. Genetic variation in this gene can give rise to lethal, early-onset diseases known as laminopathies. Here, we analyze the literature and conduct computational analyses of lamin A signaling and intracellular interactions in order to examine potential mechanisms for altering or slowing down aberrant Lamin A expression and/or for restoring the ratio of normal to aberrant lamin A. The ultimate goal of such studies is to ameliorate or combat laminopathies and related diseases of aging, and we provide a discussion of current approaches in this review.

Old and new antiarrhythmic drugs for converting and maintaining sinus rhythm in atrial fibrillation: comparative efficacy and results of trials

In managing atrial fibrillation (AF), the main therapeutic strategies include rate control, termination of the arrhythmia, and the prevention of recurrences and thromboembolic events. Safety and efficacy considerations are important in optimizing the choice of an antiarrhythmic drug for the treatment of AF. Recently approved antiarrhythmics, such as dofetilide, and promising investigational drugs, such as azimilide and dronedarone, may change the treatment landscape for AF. For medical conversion of recent-onset AF, class IC antiarrhythmic drugs, administered as an oral bolus, have been demonstrated to be the most efficacious pharmacologic conversion agents. Intravenous ibutilide and oral dofetilide both have efficacies superior to placebo in controlled trials for converting persistent AF. Comparative trials in paroxysmal AF have demonstrated that flecainide, propafenone, quinidine, and sotalol are equally effective in preventing recurrences of AF. Amiodarone has been demonstrated to be more efficacious than propafenone or sotalol in the Canadian Trial of Atrial Fibrillation. In persistent AF, twice-daily dofetilide has been shown to be as or more effective than low-dose sotalol given twice daily for the maintenance of sinus rhythm in patients with AF. Trials have demonstrated that subjective adverse effects are less frequent with class IC drugs, sotalol, and dofetilide compared with such drugs as quinidine. In patients without structural heart disease, flecainide, propafenone, and D,L-sotalol are the initial drugs of choice, given their reasonable efficacy, low incidence of subjective side effects, and lack of significant end-organ toxicity. Treating AF in patients with left ventricular dysfunction can be difficult because of associated electrophysiologic derangements, potential proarrhythmic concerns, and negative inotropic effects of antiarrhythmics. Some data exist suggesting that angiotensin-converting enzyme inhibitors and angiotensin receptor blockers can prevent AF either by preventing atrial dilation and stretch-induced arrhythmias or by blocking the renin-angiotensin system. In post-myocardial infarction patients, D,L-sotalol, dofetilide, and amiodarone-and in congestive heart failure patients, amiodarone and dofetilide-have demonstrated neutral effects on survival in controlled trials. In the Congestive Heart Failure Survival Trial of Antiarrhythmic Therapy (CHF-STAT), amiodarone lowered the frequency of AF development and improved left ventricular ejection fraction over time. In CHF-STAT, there was lower mortality in patients who converted from AF to sinus rhythm. Dofetilide decreased rehospitalization for congestive heart failure in the Danish Investigations of Arrhythmia and Mortality on Dofetilide (DIAMOND) trials. Neutral effects on survival and favorable hemodynamics have positioned amiodarone and dofetilide as the antiarrhythmics of choice in patients with left ventricular dysfunction. In post-myocardial infarction patients, sotalol is an additional agent to consider for treatment of AF in this setting.

Proarrhythmia

Proarrhythmia is defined as the aggravation of an existing arrhythmia or the development of a new arrhythmia secondary to antiarrhythmic drug. Proarrhythmic events include drug-induced bradyarrhythmias, atrial and ventricular proarrhythmias. New onset sustained or incessant ventricular tachycardia and torsade de pointes can be life threatening. This article reviews the incidence, aggravating factors, and treatment of proarrhythmia.

Neurodevelopment after in utero amiodarone exposure

It is not known whether amiodarone is neurotoxic to the fetus, as it is to adults. We evaluated neurodevelopment of a historical cohort (N = 10) of children exposed transplacentally to amiodarone. Scores on standardized tests of cognitive and language skills were compared (by Wilcoxon signed rank test) between eight toddlers and matched controls. It was not possible to obtain controls for older amiodarone-exposed children (aged 9.7 and 12.0 years), whose test results were compared descriptively with normative data. There was no difference in IQ scores between amiodarone-exposed toddlers and controls. All had favorable temperaments. However, amiodarone-exposed toddlers showed expressive language skills that were relatively poorer than verbal skills, when compared with controls (p = 0.046). One amiodarone-exposed toddler exhibited global developmental delay. The older amiodarone-exposed children had well-developed social competence, favorable global IQ scores, but problems with reading comprehension, written language, and arithmetic. This picture is reminiscent of the Nonverbal Learning Disability Syndrome. There may be neurotoxicity associated with transplacental exposure to amiodarone. Follow-up is warranted, although most mothers were happy with the development of their children.

Pregnancy outcome after gestational exposure to amiodarone in Canada

OBJECTIVE

Our purpose was to quantitate the risk of perinatal thyroid dysfunction and other amiodarone-induced adverse effects among infants exposed in utero to amiodarone.

STUDY DESIGN

A historic cohort study of gestational exposure to amiodarone was conducted by contacting Canadian cardiac electrophysiologists.

RESULTS

Twelve cases were identified. Of six with first-trimester exposure, one child had congenital nystagmus with synchronous head titubation. There was one case each of transient neonatal hypothyroidism (9%) and hyperthyroidism (9%). A fourth child, exposed to amiodarone from 20 weeks' gestation, had developmental delay, hypotonia, hypertelorism, and micrognathia. Four small-for-gestational-age infants were also exposed to beta-blockers, which in addition to maternal cardiac disease, have been recognized to cause growth restriction. beta-Blockers may also have contributed to bradycardia in one of the three fetuses in whom this was observed.

CONCLUSIONS

Gestational exposure to amiodarone may be complicated by perinatal hypothyroidism or hyperthyroidism and possibly neurologic abnormalities, intrauterine growth retardation or fetal bradycardia. Concomitant beta-blocker therapy should probably be avoided. Full neonatal thyroid function tests and developmental follow-up are recommended.

Amiodarone. An overview of its pharmacological properties, and review of its therapeutic use in cardiac arrhythmias

Amiodarone, originally developed over 20 years ago, is a potent antiarrhythmic drug with the actions of all antiarrhythmic drug classes. It has been successfully used in the treatment of symptomatic and life-threatening ventricular arrhythmias and symptomatic supraventricular arrhythmias. In patients with left ventricular dysfunction amiodarone does not usually produce any clinically significant cardiodepression and the drug has relatively high antiarrhythmic efficacy. Preliminary studies indicate that amiodarone may have a beneficial effect on mortality and survival in certain groups of patients with ventricular arrhythmias, an action probably related to both its antiarrhythmic and antifibrillatory effects. The adverse effect profile of amiodarone is diverse, involving the cardiac, thyroid, pulmonary, hepatic, gastrointestinal, ocular, neurological and dermatological systems. Interstitial pneumonitis and hepatitis are potentially fatal, but the vast majority of adverse events are less serious, and some may be dose dependent. Pretreatment monitoring, regular assessments and the use of minimum effective doses are, therefore, necessary. Thus, with appropriate monitoring to control its well recognised adverse effects amiodarone has an important place as an effective 'broad spectrum' antiarrhythmic drug which has, so far, been used when other treatments have proved ineffective. More recent preliminary data also suggest that it may also have a beneficial effect in the prevention of sudden death in some patients.

Prevention and management of drug-induced peripheral neuropathy

When symptoms of peripheral neuropathy appear, the possibility that they have been induced by drugs should be considered. A large number of drugs of all kinds, several of which are considered indispensable, have been implicated in peripheral neuropathy. A list of some of these drugs is provided. Neuropathy is a universal and dose-limiting factor during treatment with vinca alkaloids, but is otherwise a rare complication of drug therapy. Drug-induced peripheral neuropathy is almost always due to a dose-dependent primary axonal degeneration caused either by toxic reactions or by metabolic changes in neurons or their surroundings. The use of drugs should be restricted, especially in patients with a risk for development of neuropathy or with already existing neuropathy, e.g. patients with hepatic or renal failure, diabetes mellitus, or malnutrition. Patients should be given vitamins, prophylactically or therapeutically, which will sometimes allow a treatment to be continued. In other cases of drug-induced neuropathy the drug should be stopped. Reversal depends on the severity of the neuropathy, intensity and duration of the treatment and existence of causative cofactors, but generally the prognosis is good. While waiting for recovery physiotherapy is of importance, and when paraesthesia and pain are troublesome the patient should be treated with carbamazepine, imipramine or lidocaine (lignocaine).