Procainamide

Major Uses

Procainamide is a Class IA anti-arrhythmic drug used to suppress abnormal electrical activity and make the heart less irritable. It is primarily used to control ventricular arrhythmias in dogs, but it is also sometimes used in cats. The drug is beneficial in the treatment of cardiomyopathy and in the treatment of cardiac arrhythmias associated with infections, metabolic illness, and surgery.

Procainamide is not approved by the Food and Drug Administration for use in animals, but it is prescribed legally as an extra-label drug by veterinarians. It is very similar to the drug quinidine and is typically taken from the time of diagnosis until the end of life.

Common Precautions

Side effects commonly associated with use of procainamide include diarrhea, vomiting, weakness, anorexia, and low blood pressure. Changes in hair color have been reported in dogs undergoing long-term treatment with the medication.

Dogs undergoing treatment with the drug may develop the autoimmune disease called systemic lupus erythematosus.

Procainamide should not be administered to animals diagnosed with myasthenia gravis because it can prevent the anticholinestearease drugs used to treat this neuromuscular disease from working. Procainamide is also not for animals experiencing second-degree or third-degree heart block.

The drug should be used cautiously in animals with liver disease and congestive heart failure.

Procainamide is known to interact with other medications and supplements, including cimetidine, succinylcholine, antihypertensive drugs, muscle relaxants, aminoglycosides, acetazolamide, digitalis, pyridostigmine, neostigmine, and certain antihistamines.

Procainamide should not be used in animals with a known allergy or hypersensitivity to the drug. Any known or suspected overdose should be reported to a veterinarian right away.

Storage

Procainamide should be stored in a cool and dry location, at room temperature, and away from direct sunlight and sources of heat. It should not be kept in the bathroom or above the kitchen sink, and it should be stored in its original packaging and out of the reach of children and animals.

Administration

Procainamide is available as an injection in concentrations of 100 mg/ml and 500 mg/ml. It is also available in tablet and capsule form in strengths of 250 mg, 375 mg, and 500 mg. Sustained release capsules are available in strengths of 250 mg, 500 mg, 750 mg, and 1,000 mg.

In dogs, the typical dose of procainamide is 3 to 10 mg/lb (6 to 20 mg/kg) IV or as a constant IV drip at 6 to 12 mcg/lb/min (12 to 25 mcg/kg/min). Orally, the drug is dosed at 5 to 10 mg/lb (10 to 20 mg/kg) every six to eight hours.

Procainamide should be given on an empty stomach and at least one-half hour before meals.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose of procainamide is missed, it should be taken as soon as possible. If it is almost time for the next dose, the missed dose should be skipped and the normal schedule resumed. Two doses of this medication should not be administered at once.