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The adverse reactions which were reported in Nor-pace clinical trials encompass observations in 1,500 patients, including 90 patients studied for at least 4 years. The most serious adverse reactions are hypo-tension 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: dry mouth (32%), urinary hesitancy (14%), constipation (11%)
The following reactions were reported in 3% to 9% of patients:
Genitourinary: urinary retention, urinary frequency and urgency
Gastrointestinal: nausea, pain/bloating/gas
General: dizziness, general fatigue/muscle weakness, headache, malaise, aches/pains
The following reactions were reported in 1% to 3% of patients:
Cardiovascular: hypotension with or without congestive heart failure, increased congestive heart failure (see WARNINGS), cardiac conduction disturbances (see WARNINGS), edema/weight gain, shortness of breath, syncope, chest pain
Dermatologic: generalized rash/dermatoses, itching
Central nervous system: nervousness
Other: hypokalemia, elevated cholesterol/triglycerides
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 Norpace administration (see WARNINGS).
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 procaina-mide following the development of LE symptoms. Rarely, acute psychosis has been reported following Norpace (disopyramide phosphate) therapy, with prompt return to normal mental status when therapy was stopped. The physician should be aware of these possible reactions and should discontinue Norpace (disopyramide phosphate) or Norpace (disopyramide phosphate) CR therapy promptly if they occur.
Read the Norpace (disopyramide phosphate) Side Effects Center for a complete guide to possible side effects
If phenytoin or other hepatic enzyme inducers are taken concurrently with Norpace (disopyramide phosphate) or Norpace (disopyramide phosphate) CR, lower plasma levels of disopyramide may occur. Monitoring of disopyramide plasma levels is recommended in such concurrent use to avoid inef-fective therapy. Other antiarrhythmic drugs (eg, quinidine, procainamide, lidocaine, propranolol) have occasionally been used concurrently with Nor-pace. 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 Norpace (disopyramide phosphate) was coadministered with either propranolol or diazepam. Concomitant administration of Norpace (disopyramide phosphate) and quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels. Norpace (disopyramide phosphate) does not increase serum digoxin levels.
Until data on possible interactions between ve-rapamil and disopyramide phosphate are obtained, disopyramide should not be administered within 48 hours before or 24 hours after verapamil administration.
Although potent inhibitors of cytochrome P450 3A4 (eg, ketoconazole) have not been studied clinically, in vitro studies have shown that erythromycin and oleandomycin inhibit the metabolism of diso-pyramide. 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 cy-tochrome 3A4 could result in potentially fatal interaction.
Read the Norpace Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 7/17/2008
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