CHF and arrhythmias:

Indications for RYTHMOL SR:

To prolong recurrence of symptomatic atrial fibrillation in patients without structural heart disease.

Adult:

Individualize. Not interchangeable on a mg-to-mg basis with immediate-release form (see full labeling). Swallow whole. Initially 225mg every 12hrs. May increase at 5-day intervals to 325mg every 12hrs; max 425mg every 12hrs. When switching from 150mg three times daily of the immediate-release form, start Rythmol SR at 325mg twice daily. QRS widening, 2nd or 3rd degree AV block, or hepatic impairment: reduce dose.

Children:

Not established.

Contraindications:

Heart failure. Cardiogenic shock. SA, AV and intraventricular disorders of impulse generation or conduction (eg, sick sinus syndrome, AV block), unless paced. Known Brugada Syndrome. Bradycardia. Marked hypotension. Bronchospastic disorders. Severe obstructive pulmonary disease. Marked electrolyte imbalance.

Boxed Warning:

Mortality.

Warnings/Precautions:

Significant proarrhythmic risk in structural heart disease. Avoid in patients with non-life-threatening ventricular arrhythmias. Monitor ECG, pacemakers before and during therapy. May provoke overt heart failure. Discontinue if ECG changes are suggestive of Brugada Syndrome. Monitor for agranulocytosis. Hepatic or renal dysfunction: monitor. Elderly. Labor & delivery, fetal/neonatal: monitor. Pregnancy. Nursing mothers.

See Also:

Pharmacologic Class:

Class IC antiarrhythmic.

Interactions:

Avoid drugs that may prolong the QT interval (eg, antiarrhythmics, some phenothiazines, tricyclic antidepressants, oral macrolides). Avoid concomitant Class IA and III antiarrhythmics (including quinidine, amiodarone). Potentiates β-blockers, warfarin, digoxin (consider reducing their doses when starting propafenone). Potentiated by CYP2D6 inhibitors (eg, desipramine, paroxetine, ritonavir, sertraline) and CYP3A4 inhibitors (eg, ketoconazole, saquinavir, erythromycin, grapefruit juice); avoid simultaneous use with both. Antagonized by rifampin. May be antagonized by orlistat. Local anesthetics may increase CNS effects.

Adverse Reactions:

Unusual taste, nausea, vomiting, dizziness, constipation, headache, fatigue, 1st degree AV block, intraventricular conduction delay, palpitations, chest pain, dyspnea, anxiety, upper respiratory tract infection, edema, influenza, angina pectoris, atrial flutter, heart failure, bradycardia, blurred vision; new or worsened arrhythmias, conduction disturbances, elevated ANA titers, exacerbation of myasthenia gravis.

Generic Availability:

YES

How Supplied:

Tabs—100; SR caps—60

Pricing for RYTHMOL SR

225mg capsule (Qty: 60)
Appx. price $154
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