Disopyramide Phosphate

Disopyramide Phosphate

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Questions & Answers

Side Effects & Adverse Reactions

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. Considering the known proarrhythmic properties of disopyramide and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of disopyramide as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias.

Negative Inotropic Properties
Heart Failure/Hypotension

Disopyramide may cause or worsen congestive heart failure or produce severe hypotension as a consequence of its negative inotropic properties. Hypotension has been observed primarily in patients with primary cardiomyopathy or inadequately compensated congestive heart failure. Disopyramide should not be used in patients with uncompensated or marginally compensated congestive heart failure or hypotension unless the congestive heart failure or hypotension is secondary to cardiac arrhythmia. Patients with a history of heart failure may be treated with disopyramide, but careful attention must be given to the maintenance of cardiac function, including optimal digitalization. If hypotension occurs or congestive heart failure worsens, disopyramide should be discontinued and, if necessary, restarted at a lower dosage only after adequate cardiac compensation has been established.

QRS Widening

Although it is unusual, significant widening (greater than 25%) of the QRS complex may occur during disopyramide administration; in such cases disopyramide should be discontinued.

Q-T Prolongation

As with other Type 1 antiarrhythmic drugs, prolongation of the Q-T interval (corrected) and worsening of the arrhythmia, including ventricular tachycardia and ventricular fibrillation, may occur. Patients who have evidenced prolongation of the Q-T interval in response to quinidine may be at particular risk. As with other Type 1A antiarrhythmics, disopyramide phosphate has been associated with torsade de pointes.

If a Q-T prolongation of greater than 25% is observed and if ectopy continues, the patient should be monitored closely, and consideration be given to discontinuing disopyramide.

Hypoglycemia

In rare instances significant lowering of blood glucose values has been reported during disopyramide administration. The physician should be alert to this possibility, especially in patients with congestive heart failure, chronic malnutrition, hepatic, renal or other diseases, or drugs (e.g., beta adrenoceptor blockers, alcohol) which could compromise preservation of the normal glucoregulatory mechanisms in the absence of food. In these patients the blood glucose levels should be carefully followed.

Concomitant Antiarrhythmic Therapy

The concomitant use of disopyramide with other Type 1A antiarrhythmic agents (such as quinidine or procainamide), Type 1C antiarrhythmics (such as encainide, flecainide or propafenone), and/or propranolol should be reserved for patients with life-threatening arrhythmias who are demonstrably unresponsive to single-agent antiarrhythmic therapy. Such use may produce serious negative inotropic effects, or may excessively prolong conduction. This should be considered particularly in patients with any degree of cardiac decompensation or those with a prior history thereof. Patients receiving more than one antiarrhythmic drug must be carefully monitored.

Heart Block

If first-degree heart block develops in a patient receiving disopyramide, the dosage should be reduced. If the block persists despite reduction of dosage, continuation of the drug must depend upon weighing the benefit being obtained against the risk of higher degrees of heart block. Development of second- or third-degree AV block or unifascicular, bifascicular, or trifascicular block requires discontinuation of disopyramide therapy, unless the ventricular rate is adequately controlled by a temporary or implanted ventricular pacemaker.

Anticholinergic Activity

Because of its anticholinergic activity, disopyramide phosphate should not be used in patients with glaucoma, myasthenia gravis, or urinary retention unless adequate overriding measures are taken; these consist of the topical application of potent miotics (e.g., pilocarpine) for patients with glaucoma, and catheter drainage or operative relief for patients with urinary retention. Urinary retention may occur in patients of either sex as a consequence of disopyramide administration, but males with benign prostatic hypertrophy are at particular risk. In patients with a family history of glaucoma, intraocular pressure should be measured before initiating disopyramide therapy. Disopyramide phosphate should be used with special care in patients with myasthenia gravis since its anticholinergic properties could precipitate a myasthenic crisis in such patients.

Legal Issues

There is currently no legal information available for this drug.

FDA Safety Alerts

There are currently no FDA safety alerts available for this drug.

Manufacturer Warnings

There is currently no manufacturer warning information available for this drug.

FDA Labeling Changes

There are currently no FDA labeling changes available for this drug.

Uses

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.

History

There is currently no drug history available for this drug.

Other Information

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:

Disopyramide Phosphate Structural Formula

Disopyramide Phosphate Structural Formula

C21H29N3O•H3PO4            M.W. 437.47

(±)-α-[2-(Diisopropylamino)ethyl]-α-phenyl-2-pyridineacetamide phosphate (1:1).

Disopyramide phosphate is freely soluble in water, and the free base (pKa 10.4) has an aqueous solubility of 1 mg/mL. The chloroform: water partition coefficient of the base is 3.1 at pH 7.2.

Disopyramide phosphate is a racemic mixture of d- and l-isomers. This drug is not chemically related to other antiarrhythmic drugs.

Disopyramide phosphate capsules (equivalent to 100 mg Disopyramide Base) and Disopyramide phosphate capsules (equivalent to 150 mg Disopyramide Base) contain the following inactive ingredients: magnesium stearate, microcrystalline cellulose and sodium lauryl sulfate. The capsule shells contain gelatin, methylparaben, propylparaben, silicon dioxide, sodium lauryl sulfate and titanium dioxide.

The 100 mg capsule shell also contains D&C Red No. 28, D&C Yellow No. 10, FD&C Blue No. 1 and FD&C Red No. 40.

The 150 mg capsule shell also contains black iron oxide and red iron oxide.

Disopyramide Phosphate Manufacturers


  • Watson Laboratories, Inc.
    Disopyramide Phosphate Capsule [Watson Laboratories, Inc.]
  • Teva Pharmaceuticals Usa Inc
    Disopyramide Phosphate Capsule [Teva Pharmaceuticals Usa Inc]
  • Avkare, Inc.
    Disopyramide Phosphate (Disopyramide Phosphate) Capsule [Avkare, Inc.]
  • Carilion Materials Management
    Disopyramide Phosphate Capsule [Carilion Materials Management]
  • Carilion Materials Management
    Disopyramide Phosphate Capsule [Carilion Materials Management]

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