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Isorythm: Full Drug Profile

Medically reviewed by Min Clinic Staff | Updated: January 2026

Isorythm - General Information

A class I anti-arrhythmic agent (one that interferes directly with the depolarization of the cardiac membrane and thus serves as a membrane-stabilizing agent) with a depressant action on the heart similar to that of guanidine. It also possesses some anticholinergic and local anesthetic properties. [PubChem]

 

Pharmacology of Isorythm

Isorythm is an antiarrhythmic drug indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia that are life-threatening. In man, Isorythm at therapeutic plasma levels shortens the sinus node recovery time, lengthens the effective refractory period of the atrium, and has a minimal effect on the effective refractory period of the AV node. Little effect has been shown on AV-nodal and His-Purkinje conduction times or QRS duration. However, prolongation of conduction in accessory pathways occurs.

 

Isorythm for patients

 

Isorythm Interactions

If phenytoin or other hepatic enzyme inducers are taken concurrently with Norpace or Norpace CR, lower plasma levels of disopyramide may occur. Monitoring of disopyramide plasma levels is recommended in such concurrent use to avoid ineffective therapy. Other antiarrhythmic drugs (eg, quinidine, procainamide, lidocaine, propranolol) have occasionally been used concurrently with Norpace. Excessive widening of the QRS complex and/or prolongation of the Q-T interval may occur in these situations. In healthy subjects, no significant drug-drug interaction was observed when Norpace was coadministered with either propranolol or diazepam. Concomitant administration of Norpace and quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels. Norpace does not increase serum digoxin levels.

Patients taking disopyramide phosphate and erythromycin concomitantly may develop increased serum concentrations of disopyramide resulting in excessive widening of the QRS complex and/or prolongation of the Q-T interval. Patients taking disopyramide phosphate and hepatic enzyme inhibitors concomitantly should be closely monitored.

Until data on possible interactions between verapamil and disopyramide phosphate are obtained, disopyramide should not be administered within 48 hours before or 24 hours after verapamil administration.

 

Isorythm Contraindications

Norpace and Norpace CR are contraindicated in the presence of cardiogenic shock, preexisting second- or third-degree AV block (if no pacemaker is present), congenital Q-T prolongation, or known hypersensitivity to the drug.

 

Additional information about Isorythm

Isorythm Indication: For the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, ventricular pre-excitation and cardiac dysrhythmias. Mechanism Of Action: Isorythm is a Type 1 antiarrhythmic drug (ie, similar to procainamide and quinidine). It inhibits the fast sodium channels. In animal studies Isorythm decreases the rate of diastolic depolarization (phase 4) in cells with augmented automaticity, decreases the upstroke velocity (phase 0) and increases the action potential duration of normal cardiac cells, decreases the disparity in refractoriness between infarcted and adjacent normally perfused myocardium, and has no effect on alpha- or beta-adrenergic receptors. Drug Interactions: Acebutolol The beta-blocker increases toxicity of disopyramideAtenolol The beta-blocker increases toxicity of disopyramideAzithromycin The macrolide increases the effect of disopyramideBetaxolol The beta-blocker increases toxicity of disopyramideBevantolol The beta-blocker increases toxicity of disopyramideBisoprolol The beta-blocker increases toxicity of disopyramideCarteolol The beta-blocker increases toxicity of disopyramideCarvedilol The beta-blocker increases toxicity of disopyramideCisapride Increased risk of cardiotoxicity and arrhythmiasClarithromycin Increased risk of cardiotoxicity and arrhythmiasDonepezil Possible antagonism of actionErythromycin Increased risk of cardiotoxicity and arrhythmiasEsmolol The beta-blocker increases toxicity of disopyramideEthotoin The hydantoin decreases the effect of disopyramideFosphenytoin The hydantoin decreases the effect of disopyramideGalantamine Possible antagonism of actionGatifloxacin Increased risk of cardiotoxicity and arrhythmiasGrepafloxacin Increased risk of cardiotoxicity and arrhythmiasLabetalol The beta-blocker increases toxicity of disopyramideLevofloxacin Increased risk of cardiotoxicity and arrhythmiasMephenytoin The hydantoin decreases the effect of disopyramideMesoridazine Increased risk of cardiotoxicity and arrhythmiasMetoprolol The beta-blocker increases toxicity of disopyramideMoxifloxacin Increased risk of cardiotoxicity and arrhythmiasNadolol The beta-blocker increases toxicity of disopyramidePenbutolol The beta-blocker increases toxicity of disopyramidePhenobarbital Phenobarbital decreases levels of disopyramidePhenytoin The hydantoin decreases the effect of disopyramidePindolol The beta-blocker increases toxicity of disopyramidePractolol The beta-blocker increases toxicity of disopyramidePropranolol The beta-blocker increases toxicity of disopyramideQuinupristin This combination presents an increased risk of toxicityRanolazine Possible additive effect on QT prolongationRifampin Rifampin decreases the effect of disopyramideRivastigmine Possible antagonism of actionSotalol The beta-blocker increases toxicity of disopyramideSparfloxacin Increased risk of cardiotoxicity and arrhythmiasTelithromycin Increased risk of cardiotoxicity and arrhythmiasTerfenadine Increased risk of cardiotoxicity and arrhythmiasThioridazine Increased risk of cardiotoxicity and arrhythmiasTimolol The beta-blocker increases toxicity of disopyramideZiprasidone Increased risk of cardiotoxicity and arrhythmiasOxprenolol The beta-blocker increases toxicity of disopyramide Food Interactions: Take without regard to meals.Avoid alcohol. Generic Name: Disopyramide Synonyms: Disopiramida [Inn-Spanish]; Disopyramide Free Base; Disopyramide Phosphate; Disopyramidum [Inn-Latin] Drug Category: Antiarrhythmic Agents Drug Type: Small Molecule; Approved Other Brand Names containing Disopyramide: Dicorantil; Isorythm; Lispine; Norpace; Norpace CR; Ritmodan; Rythmodan; Rythmodan P; Rythmodan-La; Searle 703; Xi-Disopyramide; Absorption: Nearly complete Toxicity (Overdose): LD50=580 mg/kg in rats Protein Binding: 50%-65% Biotransformation: Hepatic Half Life: 6.7 hours (range 4-10 hours) Dosage Forms of Isorythm: Tablet, extended release OralCapsule Oral Chemical IUPAC Name: 4-(di(propan-2-yl)amino)-2-phenyl-2-pyridin-2-ylbutanamide Chemical Formula: C21H29N3O Disopyramide on Wikipedia: https://en.wikipedia.org/wiki/Disopyramide Organisms Affected: Humans and other mammals