Antiarrhythmics adverse reactions

Discuss the uses, general drug actions, general adverse reactions, contraindications, precautions, and interactions of the antiarrhythmic drugs. 

Discuss ways to promote an optimal response to therapy, how to manage common adverse reactions, and important points to keep in mind when educating patients about the use of antiarrhythmic drugs. 

Coadministration of ritonavir with certain nonsedating antihistamines, sedative hypnotics, antiarrhythmics, or ergot alkaloid preparations may result in potentially serious and/or life-threatening adverse reactions due to possible effects of ritonavir on the hepatic metabolism of certain drugs (see Contraindications). 

Antiarrhythmic therapy carries with it a number of risks. In some cases, the risk of an adverse reaction is clearly related to high dosages or plasma concentrations. Examples include lidocaine-induced tremor or quinidine-induced cinchonism. In other cases, adverse reactions are unrelated to high plasma concentrations (eg, procainamide-induced agranulocytosis). For many serious adverse reactions to antiarrhythmic drugs, the combination of drug therapy and the underlying heart disease appears important. 

Hilleman DE, Mohiuddin SM, Garmon JM. Adverse reactions during acute and chronic class I antiarrhythmic therapy. Curr Ther Res 1992 51 730-8. 

The therapeutic range is bounded by a plasma concentration below which no dierapeutic effect is likely, and an upper concentration above which the risk of adverse effects increases. As discussed in the text, many serious adverse reactions to antiarrhythmic drugs can occur at dierapeutic concentrations in susceptible individuals. When only an upper limit is cited, a lower limit has not been well defined. Variable generation of active metabolites may furdier complicate die interpretation of plasma concentration data (Chapters 1 Pharmacokinetics The Dynamics of Drug Absorption, Distribution, and Elimination and 5 Principles of Therapeutics). 

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