Disopyramide Phosphate

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Overview

What is Disopyramide Phosphate?

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:

CHNO∙HPO 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 and 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.

What does Disopyramide Phosphate look like?

What are the available doses of Disopyramide Phosphate?

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What should I talk to my health care provider before I take Disopyramide Phosphate?

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How should I use Disopyramide Phosphate?

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.

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. 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, as discussed below, should not be given, and initial dosage should be limited to 100 mg every 6 to 8 hours.

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 (100 mg every 6 hours).

For patients with severe renal insufficiency (C 40 mL/min or less), the recommended dosage regimen of disopyramide is 100 mg at intervals shown in the table below, with or without an initial loading dose of 150 mg.

For patients in whom rapid control of ventricular arrhythmia is essential, an initial loading dose of 300 mg disopyramide (200 mg for patients whose body weight is less than 110 pounds) is recommended, followed by the appropriate maintenance dosage. Therapeutic effects are usually attained 30 minutes to 3 hours after administration of a 300 mg loading dose. If there is no response or evidence of toxicity within 6 hours of the loading dose, 200 mg of disopyramide every 6 hours may be prescribed instead of the usual 150 mg. If there is no response to this dosage within 48 hours, either disopyramide should then be discontinued or the physician should consider hospitalizing the patient for careful monitoring while subsequent disopyramide doses of 250 mg or 300 mg every 6 hours are given. A limited number of patients with severe refractory ventricular tachycardia have tolerated daily doses of disopyramide up to 1600 mg per day (400 mg every 6 hours), resulting in disopyramide plasma levels up to 9 mcg/mL. If such treatment is warranted, it is essential that patients be hospitalized for close evaluation and continuous monitoring.

What interacts with Disopyramide Phosphate?

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.

What are the warnings of 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 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

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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.

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What are the precautions of Disopyramide Phosphate?

General

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Patients with atrial flutter or fibrillation should be digitalized prior to disopyramide administration to ensure that drug-induced enhancement of AV conduction does not result in an increase of ventricular rate beyond physiologically acceptable limits.

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Care should be taken when prescribing disopyramide for patients with sick sinus syndrome (bradycardia-tachycardia syndrome), Wolff-Parkinson-White syndrome (WPW), or bundle branch block. The effect of disopyramide phosphate in these conditions is uncertain at present.

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Patients with myocarditis or other cardiomyopathy may develop significant hypotension in response to the usual dosage of disopyramide phosphate, probably due to cardiodepressant mechanisms. Therefore, a loading dose of disopyramide should not be given to such patients, and initial dosage and subsequent dosage adjustments should be made under close supervision (see ).

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More than 50% of disopyramide is excreted in the urine unchanged. Therefore disopyramide phosphate dosage should be reduced in patients with impaired renal function (see ). The electrocardiogram should be carefully monitored for prolongation of PR interval, evidence of QRS widening, or other signs of overdosage (see ).

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Hepatic impairment also causes an increase in the plasma half-life of disopyramide. Dosage should be reduced for patients with such impairment. The electrocardiogram should be carefully monitored for signs of overdosage (see ).

Patients with cardiac dysfunction have a higher potential for hepatic impairment; this should be considered when administering disopyramide.

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Antiarrhythmic drugs may be ineffective in patients with hypokalemia, and their toxic effects may be enhanced in patients with hyperkalemia. Therefore, potassium abnormalities should be corrected before starting disopyramide therapy.

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 ). In healthy subjects, no significant drug-drug interaction was observed when disopyramide was coadministered with either propranolol or diazepam. Concomitant administration of disopyramide and quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels. Disopyramide does not increase serum digoxin levels.

Until data on possible interactions between verapamil and disopyramide phosphate are obtained, disopyramide should not be administered within 48 hours before or 24 hours after verapamil administration.

Although potent inhibitors of CYP3A4 (e.g., ketoconazole) have not been studied clinically, studies have shown that erythromycin and oleandomycin inhibit the metabolism of disopyramide. Cases of life-threatening interactions have been reported for disopyramide when given with clarithromycin and erythromycin indicating that co-administration of disopyramide with inhibitors of CYP3A4 could result in potentially fatal interaction.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Eighteen months of disopyramide phosphate administration to rats, at oral doses up to 400 mg/kg/day (about 30 times the usual daily human dose of 600 mg/day, assuming a patient weight of at least 50 kg), revealed no evidence of carcinogenic potential. An evaluation of mutagenic potential by Ames test was negative. Disopyramide, at doses up to 250 mg/kg/day, did not adversely affect fertility of rats.

Pregnancy

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Labor and Delivery

It is not known whether the use of disopyramide during labor or delivery has immediate or delayed adverse effects on the fetus, or whether it prolongs the duration of labor or increases the need for forceps delivery or other obstetric intervention.

Nursing Mothers

Studies in rats have shown that the concentration of disopyramide and its metabolites is between one and three times greater in milk than it is in plasma. Following oral administration, disopyramide has been detected in human milk at a concentration not exceeding that in plasma. Because of the potential for serious adverse reactions in nursing infants from disopyramide, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established (see ).

Geriatric Use

Clinical studies of disopyramide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Because of its anticholinergic activity, disopyramide phosphate should not be used in patients with glaucoma, urinary retention, or benign prostatic hypertrophy (medical conditions commonly associated with the elderly) unless adequate overriding measures are taken (see ). In the event of increased anticholinergic 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. This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function (see and ).

What are the side effects of Disopyramide Phosphate?

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.

The following reactions were reported in 10% to 40% of patients:

Anticholinergic:

The following reactions were reported in 3% to 9% of patients:

Anticholinergic:

Genitourinary:

Gastrointestinal:

General:

The following reactions were reported in 1% to 3% of patients:

Genitourinary:

Cardiovascular:

Gastrointestinal:

Dermatologic:

Central nervous system:

Other:

The following reactions were reported in less than 1%:

Depression, insomnia, dysuria, numbness/tingling, elevated liver enzymes, AV block, elevated BUN, elevated creatinine, decreased hemoglobin/hematocrit

Hypoglycemia has been reported in association with disopyramide administration (see ).

Infrequent occurrences of reversible cholestatic jaundice, fever, and respiratory difficulty have been reported in association with disopyramide therapy, as have rare instances of thrombocytopenia, reversible agranulocytosis, and gynecomastia. Some cases of LE (lupus erythematosus) symptoms have been reported; most cases occurred in patients who had been switched to disopyramide from procainamide following the development of LE symptoms. Rarely, acute psychosis has been reported following disopyramide therapy, with prompt return to normal mental status when therapy was stopped. The physician should be aware of these possible reactions and should discontinue disopyramide phosphate therapy promptly if they occur.

To report SUSPECTED ADVERSE EVENTS, contact Mayne Pharma at 1-844-825-8500 or FDA at 1-800-FDA-1088 or http://www.fda.gov/ for voluntary reporting of adverse reactions.

What should I look out for while using Disopyramide Phosphate?

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.

What might happen if I take too much Disopyramide Phosphate?

How should I store and handle Disopyramide Phosphate?

Disopyramide Phosphate Capsules (equivalent to 100 mg disopyramide base) are opaque orange capsules imprinted supplied in bottles of 100.Disopyramide Phosphate Capsules (equivalent to 150 mg disopyramide base) are opaque brown capsules imprinted supplied in bottles of 100.Dispense in a well-closed container with child-resistant closure.Disopyramide Phosphate Capsules (equivalent to 100 mg disopyramide base) are opaque orange capsules imprinted supplied in bottles of 100.Disopyramide Phosphate Capsules (equivalent to 150 mg disopyramide base) are opaque brown capsules imprinted supplied in bottles of 100.Dispense in a well-closed container with child-resistant closure.Disopyramide Phosphate Capsules (equivalent to 100 mg disopyramide base) are opaque orange capsules imprinted supplied in bottles of 100.Disopyramide Phosphate Capsules (equivalent to 150 mg disopyramide base) are opaque brown capsules imprinted supplied in bottles of 100.Dispense in a well-closed container with child-resistant closure.

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Clinical Information

Chemical Structure

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Clinical Pharmacology

Disopyramide phosphate is a Type 1 antiarrhythmic drug (i.e., similar to procainamide and quinidine). disopyramide decreases the rate of diastolic depolarization (phase 4) in cells with augmented automaticity, decreases the upstroke velocity (phase 0) and increases the action potential duration of normal cardiac cells, decreases the disparity in refractoriness between infarcted and adjacent normally perfused myocardium, and has no effect on alpha- or beta-adrenergic receptors.

Non-Clinical Toxicology

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.

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 ). In healthy subjects, no significant drug-drug interaction was observed when disopyramide was coadministered with either propranolol or diazepam. Concomitant administration of disopyramide and quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels. Disopyramide does not increase serum digoxin levels.

Until data on possible interactions between verapamil and disopyramide phosphate are obtained, disopyramide should not be administered within 48 hours before or 24 hours after verapamil administration.

Although potent inhibitors of CYP3A4 (e.g., ketoconazole) have not been studied clinically, studies have shown that erythromycin and oleandomycin inhibit the metabolism of disopyramide. Cases of life-threatening interactions have been reported for disopyramide when given with clarithromycin and erythromycin indicating that co-administration of disopyramide with inhibitors of CYP3A4 could result in potentially fatal interaction.

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.

The following reactions were reported in 10% to 40% of patients:

Anticholinergic:

The following reactions were reported in 3% to 9% of patients:

Anticholinergic:

Genitourinary:

Gastrointestinal:

General:

The following reactions were reported in 1% to 3% of patients:

Genitourinary:

Cardiovascular:

Gastrointestinal:

Dermatologic:

Central nervous system:

Other:

The following reactions were reported in less than 1%:

Depression, insomnia, dysuria, numbness/tingling, elevated liver enzymes, AV block, elevated BUN, elevated creatinine, decreased hemoglobin/hematocrit

Hypoglycemia has been reported in association with disopyramide administration (see ).

Infrequent occurrences of reversible cholestatic jaundice, fever, and respiratory difficulty have been reported in association with disopyramide therapy, as have rare instances of thrombocytopenia, reversible agranulocytosis, and gynecomastia. Some cases of LE (lupus erythematosus) symptoms have been reported; most cases occurred in patients who had been switched to disopyramide from procainamide following the development of LE symptoms. Rarely, acute psychosis has been reported following disopyramide therapy, with prompt return to normal mental status when therapy was stopped. The physician should be aware of these possible reactions and should discontinue disopyramide phosphate therapy promptly if they occur.

To report SUSPECTED ADVERSE EVENTS, contact Mayne Pharma at 1-844-825-8500 or FDA at 1-800-FDA-1088 or http://www.fda.gov/ for voluntary reporting of adverse reactions.

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Reference

This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
"https://dailymed.nlm.nih.gov/dailymed/"

While we update our database periodically, we cannot guarantee it is always updated to the latest version.

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Clonazepam Description Each single-scored tablet, for oral administration, contains 0.5 mg, 1 mg, or 2 mg Clonazepam, USP, a benzodiazepine. Each tablet also contains corn starch, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and povidone. Clonazepam tablets USP 0.5 mg contain Yellow D&C No. 10 Aluminum Lake. Clonazepam tablets USP 1 mg contain Yellow D&C No. 10 Aluminum Lake, as well as FD&C Blue No. 1 Aluminum Lake. Chemically, Clonazepam, USP is 5-(o-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one. It is a light yellow crystalline powder. It has the following structural formula: C15H10ClN3O3 M.W. 315.72

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Interactions

A total of 440 drugs (1549 brand and generic names) are known to interact with Imbruvica (ibrutinib). 228 major drug interactions (854 brand and generic names) 210 moderate drug interactions (691 brand and generic names) 2 minor drug interactions (4 brand and generic names) Show all medications in the database that may interact with Imbruvica (ibrutinib).

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