Disopyramide phosphate, -[2(diisopropylamino)ethyl]- -phenyl-2-pyridineacetamidephosphate (Norpace), is an oral and intravenousclass IA antiarrhythmic agent. It is quite similar to quinidineand procainamide in its electrophysiological properties, inthat it decreases phase 4 diastolic depolarization, decreasesconduction velocity, and has vagolytic properties.31 It is usedclinically in the treatment of refractory, life-threatening ventriculartachyarrhythmias. Oral administration of the drugproduces peak plasma levels within 2 hours. The drug isbound approximately 50% to plasma protein and has a halflifeof 6.7 hours in humans. More than 50% is excretedunchanged in the urine. Therefore, patients with renal insufficiencyshould be monitored carefully for evidence ofoverdose. Disopyramide phosphate commonly exhibits sideeffects of dry mouth, constipation, urinary retention, andother cholinergic blocking actions because of its structuralsimilarity to anticholinergic drugs.
