Disopyramide Phosphate
Generic Name: disopyramide phosphate
Brand Names:
Disopyramide Phosphate
DESCRIPTION Disopyramide phosphate is an antiarrhythmic drug available for oral administration in immediate-release capsules containing 100 mg or 150 mg of disopyramide base, present as the phosphate. The base content of the phosphate salt is 77.6%. The structural formula of disopyramide phosphate is: C 21 H 29 N 3 O∙H 3 PO 4 M.W. 437.47 (±)-α-[2-(Diisopropylamino)ethyl]-α-phenyl-2-pyridineacetamide phosphate (1:1).
Overview
DESCRIPTION Disopyramide phosphate is an antiarrhythmic drug available for oral administration in immediate-release capsules containing 100 mg or 150 mg of disopyramide base, present as the phosphate. The base content of the phosphate salt is 77.6%. The structural formula of disopyramide phosphate is: C 21 H 29 N 3 O∙H 3 PO 4 M.W. 437.47 (±)-α-[2-(Diisopropylamino)ethyl]-α-phenyl-2-pyridineacetamide phosphate (1:1).
Uses
INDICATIONS AND USAGE Disopyramide phosphate capsules are indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgment of the physician, are life-threatening. Because of the proarrhythmic effects of disopyramide, its use with lesser arrhythmias is generally not recommended. Treatment of patients with asymptomatic ventricular premature contractions should be avoided. Initiation of disopyramide treatment, as with other antiarrhythmic agents used to treat life-threatening arrhythmias, should be carried out in the hospital. Antiarrhythmic drugs have not been shown to enhance survival in patients with ventricular arrhythmias.
Dosage
DOSAGE AND ADMINISTRATION The dosage of disopyramide (as the phosphate) must be individualized for each patient on the basis of response and tolerance. The usual adult dosage of disopyramide is 400 to 800 mg (calculated as the disopyramide base) per day given in divided doses. The recommended dosage for most adults is 600 mg/day given in divided doses (150 mg every 6 hours). For patients whose body weight is less than 110 pounds (50 kg), the recommended dosage is 400 mg/day given in divided doses (100 mg every 6 hours). In the event of increased anticholinergic side effects, plasma levels of disopyramide should be monitored and the dose of the drug adjusted accordingly.
Side Effects
ADVERSE REACTIONS The adverse reactions which were reported in disopyramide phosphate clinical trials encompass observations in 1,500 patients, including 90 patients studied for at least 4 years. The most serious adverse reactions are hypotension and congestive heart failure. The most common adverse reactions, which are dose dependent, are associated with the anticholinergic properties of the drug. These may be transitory, but may be persistent or can be severe. Urinary retention is the most serious anticholinergic effect.
Interactions
Drug Interactions If phenytoin or other hepatic enzyme inducers are taken concurrently with disopyramide, 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 (e.g., quinidine, procainamide, lidocaine, propranolol) have occasionally been used concurrently with disopyramide. Excessive widening of the QRS complex and/or prolongation of the Q-T interval may occur in these situations (see WARNINGS ). In healthy subjects, no significant drug-drug interaction was observed when disopyramide was coadministered with either propranolol or diazepam.
Warnings
Mortality In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life threatening ventricular arrhythmias who had had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or nonfatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to careful... WARNINGS Mortality In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life threatening ventricular arrhythmias who had had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or nonfatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to carefully matched placebo-treated groups (3%). The average duration of treatment with encainide or flecainide in this study was 10 months. The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) is uncertain. CONTRAINDICATIONS Disopyramide phosphate capsules 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.
Pregnancy
Pregnancy Teratogenic Effects Pregnancy Category C Disopyramide was associated with decreased numbers of implantation sites and decreased growth and survival of pups when administered to pregnant rats at 250 mg/kg/day (20 or more times the usual daily human dose of 12 mg/kg, assuming a patient weight of at least 50 kg), a level at which weight gain and food consumption of dams were also reduced. Increased resorption rates were reported in rabbits at 60 mg/kg/day (5 or more times the usual daily human dose). Effects on implantation, pup growth, and survival were not evaluated in rabbits.
Storage
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature].
Frequently Asked Questions
What is Disopyramide Phosphate used for?▼
INDICATIONS AND USAGE Disopyramide phosphate capsules are indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgment of the physician, are life-threatening. Because of the proarrhythmic effects of disopyramide, its use with lesser arrhythmias is generally not recommended. Treatment of patients with asymptomatic ventricular premature contractions should be avoided. Initiation of disopyramide treatment, as with other antiarrhythmic agents used to treat life-threatening arrhythmias, should be carried out in the hospital. Antiarrhythmic drugs have not been shown to enhance survival in patients with ventricular arrhythmias.
What are the side effects of Disopyramide Phosphate?▼
ADVERSE REACTIONS The adverse reactions which were reported in disopyramide phosphate clinical trials encompass observations in 1,500 patients, including 90 patients studied for at least 4 years. The most serious adverse reactions are hypotension and congestive heart failure. The most common adverse reactions, which are dose dependent, are associated with the anticholinergic properties of the drug. These may be transitory, but may be persistent or can be severe. Urinary retention is the most serious anticholinergic effect.
Can I take Disopyramide Phosphate during pregnancy?▼
Pregnancy Teratogenic Effects Pregnancy Category C Disopyramide was associated with decreased numbers of implantation sites and decreased growth and survival of pups when administered to pregnant rats at 250 mg/kg/day (20 or more times the usual daily human dose of 12 mg/kg, assuming a patient weight of at least 50 kg), a level at which weight gain and food consumption of dams were also reduced. Increased resorption rates were reported in rabbits at 60 mg/kg/day (5 or more times the usual daily human dose). Effects on implantation, pup growth, and survival were not evaluated in rabbits.
What are the important warnings for Disopyramide Phosphate?▼
Mortality In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life threatening ventricular arrhythmias who had had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or nonfatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to careful... WARNINGS Mortality In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life threatening ventricular arrhythmias who had had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or nonfatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to carefully matched placebo-treated groups (3%). The average duration of treatment with encainide or flecainide in this study was 10 months. The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) is uncertain. CONTRAINDICATIONS Disopyramide phosphate capsules 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.
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Medical Disclaimer
This drug information is for educational purposes only and should not replace professional medical advice. Drug information is sourced from the FDA National Drug Code Directory and Structured Product Labeling. Always consult with a healthcare provider before starting, stopping, or changing any medication.