The importance of pharmacokinetics and pharmacodynamics in the clinical evaluation of antiarrhythmic drugs.

Many pharmacokinetic and pharmacodynamic factors affect clinical evaluation of antiarrhythmic agents. The route of administration and the duration of treatment are variables that influence the study outcome. Due to metabolic differences and pharmacodynamic factors, different results may be obtained depending on whether drugs are administered orally or intravenously. Moreover the achievement of steady state blood level does not insure the achievement of adequate myocardial drug level nor does it indicate that a steady state effect has been achieved. There may be significant delay in the accumulation of antiarrhythmic drugs in the myocardium. Only when the metabolic profile and pharmacodynamic characteristics of a drug are understood can the most efficient testing protocol be designed for a particular antiarrhythmic agent.