By Rania Gollakner, BS, DVM, MPH

What is procainamide?

Procainamide (brand name: Pronestyl®, Biocoryl®, Procan®, Procanbid®) is an antiarrhythmic drug used in dogs and horses to treat abnormal heart rhythms such as atrial fibrillation, ventricular premature complexes, and ventricular tachycardia.

Its use in dogs and horses to treat abnormal heart rhythms is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How is procainamide given?

Procainamide is given by mouth in the form of a capsule, tablet, or is given by injection into the vein in the hospital setting. When giving by mouth, give the medication on an empty stomach, at least 1 hour prior to feeding.

This medication should take effect within 1 to 2 hours and clinical signs should improve shortly after.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects may include loss of appetite, vomiting, diarrhea, weakness, low blood pressure, less effective heart beats, and rhythm abnormalities. Fevers and low white blood cell counts can also occur.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Procainamide should not be used in pets that are allergic to it or related drugs, or in pets with myasthenia gravis, torsade de pointes, cardiac glycoside intoxication, or heart block. It should also be avoided in Doberman Pinschers and Boxers. Use cautiously in patients with severe liver, kidney, or heart disease, or in pets that are generally critically ill.

It should be used with caution in pregnant and lactating pets; and a milk replacer should be considered if using this medication longer term.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with procainamide: amiodarone, amitriptyline, anticholinesterase agents, azithromycin, azole antifungals, bupropion, cisapride, clomipramine, erythromycin, fluoroquinolones, fluoxetine, H2 antagonists, hydroxychloroquine, hypotensive drugs, isoflurane, lidocaine, methadone, metronidazole, neuromuscular blocking agents, ondansetron, phenytoin, propranolol, quinidine, sodium phosphate, sotalol, trazodone, or trimethoprim.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

For long term use, serum levels should be checked periodically. Pets should be monitored for signs of toxicity, such as lethargy, confusion, decreased urination, low blood pressure, and nausea and vomiting.

How do I store procainamide?

The solution may be stored at room temperature, but do not use if the color becomes darker than a light amber color.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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