FDA BLACK BOX WARNING! INCREASED RISK OF DEATH
In the National Heart, Lung, and Blood Institute’s Cardiac Arrhythmia Suppression Trial (CAST) (a long-term, multicentered, randomized, double-blind study), in patients with asymptomatic non-life-threatening ventricular (the large chambers of the heart) arrhythmias (rhythm disturbances) who had a heart attack more than six days but less than two years previous, deaths or nonfatal cardiac arrest were seen in 7.7% of those patients treated with encainide or flecainide, members of the Class 1 group of antiarrhythmic drugs, compared to 3.0% in patients receiving an inactive sugar pill or placebo.
Because of the known ability of the Class 1 drugs, such as quinidine, to cause rhythm disturbances, and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening heart rhythm disturbances, the use of the Class 1 drugs should be reserved for patients with life-threatening rhythm disturbances of the ventricles. These warnings now appear in the FDA-approved product labeling, or package insert, for all Class 1 drugs, including: disopyramide (NORPACE and generics), flecainide (TAMBOCOR), mexiletine (MEXITIL and generics), moricizine (ETHMOZINE), procainamide (PROCANBID and generics), propafenone (RYTHMOL), quinidine (DURAQUIN, QUINAGLUTE DURA-TABS, QUINIDEX, and generics), and tocainide (TONOCARD).
FDA BLACK BOX WARNING
Positive ANA Titer: The prolonged administration of procainamide often leads to the development of a positive antinuclear antibody (ANA) test, with or without symptoms of lupus erythematosus–like syndrome. If a positive ANA titer develops, the benefits versus risks of continued procainamide therapy should be assessed.
FDA BLACK BOX WARNING
BLOOD DYSCRASIAS (disorders)
Agranulocytosis, bone marrow depression, neutropenia, hypoplastic anemia, and thrombocytopenia have been reported in patients receiving procainamide hydrochloride at a rate of approximately 0.5%. Most patients received procainamide hydrochloride within the recommended dosage range. Fatalities have occurred (with approximately 20–25% mortality in reported cases of agranulocytosis). Since most of these events have been noted during the first 12 weeks of therapy, it is recommended that complete blood counts, including white cell, differential, and platelet counts, be performed at weekly intervals for the first 3 months of therapy, and periodically thereafter. Complete blood counts should be performed promptly if the patient develops any signs of infection (such as fever, chills, sore throat, or stomatitis), bruising, or bleeding. If any of these hematologic disorders are identified, procainamide hydrochloride should be discontinued. Blood counts usually return to normal within 1 month of discontinuation. Caution should be used in patients with preexisting marrow failure or cytopenia of any type.
When this drug was used to treat rhythm disturbances of the small chambers of the heart (atria), it provided no survival advantage and a higher risk of serious adverse effects than older drugs such as digoxin, the beta-blockers, and the calcium channel blockers diltiazem and verapamil.,
This drug is not approved by the FDA to treat rhythm disturbances of the atria.