Does Pronestyl (procainamide) cause side effects?

Pronestyl (procainamide) is an antiarrhythmic drug used to treat abnormal heart rhythms such as

Three actions are responsible for its ability to correct disturbances of rhythm and prevent their recurrence. Pronestyl

  • decreases the speed of electrical conduction through the heart muscle,
  • prolongs the electrical phase during which the heart's muscle cells can be electrically stimulated, and
  • prolongs the recovery period during which the heart muscle cells cannot be stimulated.

The brand name Pronesty is no longer available in the U.S.

Common side effects of Pronestyl include

Serious side effects of Pronestyl include

A syndrome resembling lupus erythematosus, including

The lupus-like syndrome is reversible after stopping the drug. Rarely, Pronestyl can cause confusion, hallucinations, and depression.

Drug interactions of Pronestyl include amiodarone, which increases the blood concentrations of Pronestyl by either decreasing the kidneys or the liver's abilities to remove Pronestyl.

  • Combining Pronestyl with thioridazine, pimozide, quinolone antibiotics, tricyclic antidepressants, and ziprasidone may increase the risk of abnormal heart beats because these drugs may also prolong the recovery period of the heart.
  • Concurrent administration of Pronestyl with other anti-arrhythmics can result in additive or antagonistic effects on the heart.

It also is unknown if Pronestyl can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Pronestyl should be given to a pregnant woman only if clearly needed.

Pronestyl is secreted in breast milk. Mothers should discontinue breastfeeding while taking Pronestyl.

What are the important side effects of Pronestyl (procainamide)?

Common reactions include

Severe reactions include

  • abnormal heartbeats,
  • seizures,
  • heart arrest, and
  • blood disorders.

 A severe reduction in white blood cell count occurs relatively rarely with procainamide therapy and is more common with the sustained-release preparations. This side effect has caused death.

For this reason, patients on sustained-release procainamide get a complete blood count test (CBC) every 2 weeks for the first 3 months of treatment. A syndrome resembling lupus erythematosus, including

The lupus-like syndrome is reversible after stopping the drug.

Rarely, procainamide can cause

Pronestyl (procainamide) side effects list for healthcare professionals


Hypotension following oral PA administration is rare. Hypotension and serious disturbances of cardiorhythm such as ventricular asystole or fibrillation are more common after. Second degree heart block has been reported in 2 of almost 500 patients taking PA orally.


A lupus erythematosus-like syndrome of arthralgia, pleural or abdominal pain, and some-times arthritis, pleural effusion, pericarditis, fever, chills, myalgia, and possibly related hematologic or skin lesions (see below) is fairly common after prolonged PA administration, perhaps more often in patients who are slow acetylators.

While some series have reported less than 1 in 500, others have reported the syndrome in up to 30 percent of patients on long term oral PA therapy. If discontinuation of PA does not reverse the lupoid symptoms, corticosteroid treatment may be effective.


Neutropenia, thrombocytopenia, or hemolytic anemia may rarely be encountered. Agranulocytosis has occurred after repeated use of PA, and deaths have been reported.


Angioneurotic edema, urticaria, pruritus, flushing, and maculopapular rash have also occurred occasionally.


Anorexia, nausea, vomiting, abdominal pain, bitter taste, or diarrhea may occur in 3 to 4 percent of patients taking oral procainamide.

Elevated Liver Enzymes

Elevations of transaminase with and without elevations of alkaline phosphatase and bilirubin have been reported. Some patients have had clinical symptoms (e.g., malaise, right upper quadrant pain). Deaths from liver failure have been reported.

Nervous System

Dizziness or giddiness, weakness, mental depression, and psychosis with hallucinations have been reported occasionally.

What drugs interact with Pronestyl (procainamide)?

If other antiarrhythmic drugs are being used, additive effects on the heart may occur with PA administration, and dosage reduction may be necessary.

Anticholinergic drugs administered concurrently with PA may produce additive antivagal effects on A-V nodal conduction, although this is not as well documented for PA as for quinidine.

Patients taking PA who require neuromuscular blocking agents such as succinylcholine may require less than usual doses of the latter, due to PA effects on reducing acetylcholine release.

Drug/Laboratory Test Interactions

Suprapharmacologic concentrations of lidocaine and meprobamate may inhibit fluorescence of PA and NAPA, and propranolol shows a native fluorescence close to the PA/NAPA peak wavelengths, so that tests which depend on fluorescence measurement may be affected.

Treatment & Diagnosis

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Medically Reviewed on 7/10/2020
FDA Prescribing Information

Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.