Disopyramide

 Action Decreases rate of diastolic depolarizations rate; decreases upstroke velocity; increases action potential duration; prolongs refractory period.

 Indications Suppression and documented prevention of ventricular arrhythmias considered to be life threatening. Unlabeled use(s): Treatment of paroxysmal supraventricular tachycardia.

 Contraindications Cardiogenic shock; pre-existing second- or third-degree atrioventricular block (if no pacemaker present); congenital Q-T prolongation; sick sinus syndrome.

 Route/Dosage

ADULTS: PO 400 to 800 mg/day in 4 divided, evenly spaced doses. CHILDREN (12 to 18 YR): PO 6 to 15 mg/kg/day in divided doses. CHILDREN (4 to 12 YR): PO 10 to 15 mg/kg/day in divided doses. CHILDREN (1 to 4 YR): PO 10 to 20 mg/kg/day in divided doses. CHILDREN (< 1 YR): PO 10 to 30 mg/kg/day in divided doses.

Severe Refractory Ventricular Tachycardia

May give PO up to 400 mg q 6 hr.

With Cardiomyopathy or Cardiac Decompensation

Limit to PO 100 mg q 6 to 8 hr initially.

Renal/Hepatic Impairment

ADULTS: PO 100 mg q 6 hr; increase to q 8 to 24 hr for patients with deteriorating renal function.

 Interactions

Antiarrhythmic agents: May cause widened QRS and prolonged QT. Erythromycin: May cause increased disopyramide plasma levels. Hydantoins: May decrease disopyramide serum levels, half-life and bioavailability. Rifampin: May decrease disopyramide serum levels.

 Lab Test Interferences None well documented.

 Adverse Reactions

CV: Hypotension; CHF; edema; shortness of breath; syncope; chest pain. CNS: Dizziness; fatigue; headache; nervousness. DERM: Rash; dermatoses; itching. EENT: Blurred vision; dry nose, eyes, throat. GI: Nausea; pain; bloating; gas; anorexia; vomiting; diarrhea; dry mouth; constipation. GU: Urinary retention, frequency and urgency; impotence; urinary hesitancy. OTHER: Muscle weakness; malaise; aches and pains; hypokalemia; weight gain; elevated cholesterol and triglycerides; hypoglycemia.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Anticholinergic activity: Use with extreme caution in patients with urinary retention, glaucoma or myasthenia gravis. Conduction abnormalities: Use with caution in patients with bundle branch block or Wolff-Parkinson-White syndrome. Heart block: Reduce dose if first-degree block occurs; drug may need to be discontinued if heart block continues. Heart failure/hypotension: May cause or aggravate CHF or produce severe hypotension, especially in patients with depressed systolic function. Potassium imbalance: Disopyramide may be ineffective in hypokalemia and have enhanced toxicity in hyperkalemia. Renal or hepatic impairment: Dosage should be reduced.

 Administration/Storage

• Have patient swallow capsules whole.
• Administer doses 6 hr apart (12 hr apart for extended release form).
• Adjust dosage according to physiologic effect and serum levels.
• Store capsules in light-resistant container.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Assess apical/radial heart rate.
• Obtain baseline 12-lead ECG.
• Correct hypokalemia before giving drug.
• Assess I&O.
• Monitor patient weight daily.
• Monitor plasma levels and therapeutic response.
• Monitor serum electrolytes.
• If blood pressure drop of 20 mm Hg occurs, notify physician immediately.
• If heart arrhythmia or increase in heart rate develops, notify physician immediately.
• If serum potassium level is higher than recommended level, notify physician.
• If serum level of drug is higher than therapeutic level, notify physician.
• If patient has urinary elimination problems, notify physician.

 Patient/Family Education

• Instruct patient how to take own BP and heart rate.
• Tell patient to keep weekly record of weight and report any change ³ 2 lb to physician.
• Instruct patient to increase roughage in diet.
• Inform patient about possibility of urinary elimination problems and instruct to notify physician if problems persist.
• Instruct patient not to crush or chew capsules.
• Advise patient about possibility of hypoglycemia and to be alert for cold sweats, drowsiness, confusion, anxiety and cool, pale skin.
• Instruct patient to take sips of water frequently, suck on ice chips or sugarless hard candy or chew sugarless gum if dry mouth occurs.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
• Instruct patient to avoid intake of alcoholic beverages or other CNS depressants.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing other tasks requiring mental alertness.