[Determination of plasma concentrations of anti-arrhythmia agents]

The measurements of the plasma concentrations of antiarrhythmic drugs is useful both for studying the pharmacokinetics and bio-availability of a drug, and for assessing the relationship between pharmacological activity and plasma levels in clinical practice so that dosages may be adapted to obtain optimal efficacity in each individual patient and to avoid side-effects caused by drugs with low therapeutic indices. Many methods are available, including spectrophotometry, spectrofluorometry, gas chromatography, liquid chromatography and immuno-enzymology. The practicability, sensitivity and specificity of these techniques are compared with respect to their objectives. Particular attention is paid to the principal antiarrhythmic agents with fairly well defined zones of efficacity: procainamide, quinidine, disopyramide, propranolol, lignocaine and mexiletine.