Molecular basis for the antigenicity of lidocaine analogs: tocainide and mexiletine

Adverse dermatologic effects of cardiovascular drug therapy: part I

Cardiovascular disease is common, affecting an increasing number of persons as the population ages. To combat this growing health problem, physicians use a multitude of medications in the treatment of their patients. Although pharmacologic therapy greatly enhances quality of life for a majority of patients, there is always the potential for an unfavorable reaction. For example, cardiovascular drugs can induce a vast array of adverse dermatologic responses. This article reviews the various cutaneous reaction patterns that can occur as a result of treatment with Class I and II antiarrhythmic agents.

Adverse dermatologic reactions from antiarrhythmic drug therapy

Undesirable cutaneous reactions to drugs may occur early or late in the course of treatment. The ingestion of drugs may also aggravate existing dermatologic conditions. The adverse dermatologic reactions from antiarrhythmic drug therapy are reviewed. The exact incidence of dermatologic side effects from cardiovascular drugs has been difficult to estimate because of sporadic reporting. In this review, the cutaneous side effects are discussed according to drug class and the type of dermatologic reaction.

Tocainide: a severe adverse reaction

Tocainide is a primary analog of lidocaine with antiarrhythmic properties used to treat ventricular rhythm disorders. A 76-year-old man with benign paroxysmal premature ventricular contractions was treated with tocainide and developed a generalized maculopapular lupoid eruption, bleeding from the lips and gingivae, vertigo, gross tremors of the extremities, fever, and short-term memory loss, which required hospitalization. The patient recovered slowly over three months with no permanent sequelae after discontinuing the drug and receiving rigorous supportive care. His excellent physical status and absence of concomitant illness contributed to an uneventful recovery. Tocainide is a potent cardioactive drug with a long biological half-life and should be used with caution.

Overview of the clinical pharmacology of antiarrhythmic drugs

Antiarrhythmic drugs have been recognized to possess 1 or more classes of antiarrhythmic action. This classification scheme is useful, but has major limitations because the available drugs and their metabolites have multiple actions. This report presents an overview of the distinguishing features of the most frequently used agents having class I or III actions. Agents with class I actions are local anesthetic agents that depress the fast inward depolarizing sodium current and thereby slow the rate of the rise of the action potential (phase 0). This category is further divided into classes IA, IB, and IC according to the degree of potency as sodium channel inhibitors, and the individual effects of the drug on action potential, conduction velocity and repolarization. Included in the spectrum of agents with class I action are quinidine, procainamide, disopyramide, lidocaine, tocainide, mexiletine, flecainide, amiodarone, encainide and lorcainide. The antiarrhythmic drugs that exert class III action lengthen repolarization and refractoriness; included in this category are amiodarone, quinidine, bretylium and sotalol. Because of the broad range of effects that antiarrhythmic agents may exert, safe and effective therapy requires a thorough familiarity with the pharmacologic profile of each drug administered and a careful evaluation of the presenting condition and the patient history. In some cases, a multiple drug regimen may be most appropriate. Various combinations such as class IA and IB agents, have been shown to slow conduction synergistically and increase refractoriness while keeping adverse effects to a minimum.

Tocainide: a new oral antiarrhythmic

Tocainide is an orally active lidocaine analog indicated for the suppression of ventricular arrhythmias. It is electrophysiologically similar to lidocaine and produces minimal hemodynamic and electrocardiographic changes. Oral bioavailability is virtually complete, elimination half-life is 11-15 hours, and 40 percent of a dose is excreted unchanged in urine. Tocainide therapy is commonly associated with gastrointestinal and neurologic side effects that generally are well tolerated. Rash, aggravation of arrhythmias, and worsening of heart failure may also occur. While tocainide does not consistently suppress arrhythmias following myocardial infarction, it does control chronic ventricular arrhythmias, being particularly effective in patients responsive to lidocaine. Tocainide has not been shown to be more effective than quinidine or procainamide. Tocainide should be a useful agent in patients who are unable to tolerate other antiarrhythmics, who are responsive to lidocaine, or who have been troubled with Q-T prolongation with or without torsade de pointes.