Disopyramide Phosphate Er
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Questions & Answers
Side Effects & Adverse Reactions
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 non-fatal 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 phosphate and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of disopyramide phosphate as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias.
Disopyramide phosphate 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 phosphate 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 phosphate but careful attention must be given to the maintenance of cardiac function, including optimal digitalization. If hypotension occurs or heart failure worsens, disopyramide phosphate should be discontinued and, if necessary, restarted at a lower dosage only after adequate cardiac compensation has been established.
Although it is unusual, significant widening (greater than 25%) of the QRS complex may occur during disopyramide phosphate administration; in such cases disopyramide phosphate should be discontinued.
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 phosphate.
In rare instances significant lowering of blood glucose values has been reported during disopyramide phosphate 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.
The concomitant use of disopyramide phosphate 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.
If first-degree heart block develops in a patient receiving disopyramide phosphate 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 phosphate therapy, unless the ventricular rate is adequately controlled by a temporary or implanted ventricular pacemaker.
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 phosphate 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 phosphate 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.
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Manufacturer Warnings
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FDA Labeling Changes
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Uses
Disopyramide Phosphate Extended-release Capsules, USP are indicated for the treatment of documented ventricular arrhythmias such as sustained ventricular tachycardia, that in the judgement 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. The extended-release capsules should not be used initially if rapid establishment of disopyramide plasma levels is desired.
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 extended-release capsules equivalent to 150 mg of disopyramide present as the phosphate. The base content of the phosphate salt is 77.66%. The structural formula of disopyramide phosphate is:
C21H29N3O.H3PO4 M.W.437.48
(±)-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 Extended-release Capsules, USP are designed to afford a gradual and consistent release of disopyramide. Thus, for maintenance therapy, Disopyramide Phosphate Extended-release Capsules, USP provide the benefit of less frequent dosing (every 12 hours) as compared with the every-6-hour dosage schedule of immediate-release capsules.
Inactive ingredients: aluminum hydrate, black iron oxide, calcium stearate, D&C Red No. 28, D&C Yellow No. 10, dibutyl sebacate, ethylcellulose, FD&C Blue No. 1, FD&C Red No. 40, gelatin, lecithin, pharmaceutical glaze, povidone, simethicone, starch, sucrose, talc and titanium dioxide.
This product meets USP Drug Release Test 2.
Sources
Disopyramide Phosphate Er Manufacturers
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Ethex
![Disopyramide Phosphate Er (Disopyramide Phosphate) Capsule, Extended Release [Ethex]](/wp-content/themes/bootstrap/assets/img/loading2.gif)
Disopyramide Phosphate Er | Ethex
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 (300 mg every 12 hours for the extended-release product). For patients whose body weight is less than 110 pounds (50 kg), the recommended dosage is 400 mg/day given in divided doses (200 mg every 12 hours for the extended-release product). In the event of increased anticholingeric side effects, plasma levels of disopyramide should be monitored and the dose of the drug adjusted accordingly. A reduction of the dose by one third, from the recommended 600 mg/day to 400 mg/day, would be reasonable, without changing the dosing interval.
For patients with cardiomyopathy or possible cardiac decompensation, a loading dose should not be given, and initial dosage should be limited to 100 mg of immediate-release disopyramide phosphate every 6 to 8 hours. Subsequent dosage adjustments should be made gradually, with close monitoring for the possible development of hypotension and/or congestive heart failure (see WARNINGS).
For patients with moderate renal insufficiency (creatinine clearance greater than 40 mL/min) or hepatic insufficiency, the recommended dosage is 400 mg/day given in divided doses (200 mg every 12 hours for the extended-release product).
Disopyramide Phosphate Extended-release Capsules, USP are not recommended for patients with severe renal insufficiency.
Disopyramide Phosphate Extended-release Capsules, USP should not be used initially if rapid establishment of disopyramide plasma levels is desired.
Transferring to Disopyramide Phosphate Extended-release Capsules, USPThe following dosage schedule based on theoretical considerations rather than experimental data is suggested for transferring patients with normal renal function from either quinidine sulfate or procainamide therapy (Type 1 antiarrhythmic agents) to Disopyramide Phosphate Extended-release Capsules, USP therapy.
Disopyramide Phosphate Extended-release Capsules, USP should be started using the regular maintenance schedule without a loading dose 6 to 12 hours after the last dose of quinidine sulfate or 3 to 6 hours after the test dose of procainamide.
In patients in whom withdrawal of quinidine sulfate or procainamide is likely to produce life-threatening arrhythmias, the physician should consider hospitalization of the patient. When transferring a patient from immediate-release disopyramide to extended-release disopyramide, the maintenance schedule of Disopyramide Phosphate Extended-release Capsules, USP may be started 6 hours after the last dose of immediate-release disopyramide phosphate capsules.
Pediatric dosageThere is no adequate data to recommend use of Disopyramide Phosphate Extended-release Capsules, USP in pediatric patients.
Disopyramide Phosphate Extended-release Capsules, USP should not be used to prepare extemporaneous suspensions.
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