Procainamide

What is procainamide?

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

Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. 

In these instances, follow your veterinarian’s directions and cautions carefully, as they 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.
• 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 as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.

Are there any potential side effects?

Procainamide may cause the following side effects:

• loss of appetite
• vomiting
• diarrhea
• weakness
• low blood pressure
• less effective heart beats
• heart rhythm abnormalities
• fever
• low white blood cell

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
• pets with myasthenia gravis
• pets with torsade de pointes
• pets with cardiac glycoside intoxication
• pets with heart block
• doberman pinscher and boxer breeds

Procainamide should be USED WITH CAUTION in:

• patients with severe liver, kidney, or heart disease
• pets that are generally critically ill
• pregnant and lactating pets (consider a milk replacer if using this medication long term)

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with procainamide:

• antibiotics, including azithromycin, erythromycin, fluoroquinolones, metronidazole and trimethoprim
• anti-arrhythmics, including amiodarone, propanolol and sotalol
• behavior medications: amitriptyline, clomipramine, fluoxetine and trazodone
• azole antifungals
• cisapride
• H2 antagonists
• hypotensive drugs
• ondansetron
• quinidine
• sodium phosphate

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

Is any monitoring needed 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?

• Store tablets at room temperature.
• Store the solution at room temperature.
• Do not use the solution if its color becomes darker than light amber.

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.