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Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication for a longer time may develop serious side effects, but with frequent visits to your doctor, this risk can be minimized. (See Warning section.)

Tell your doctor immediately if any of these unlikely but serious side effects occur: symptoms of liver problems (e.g., persistent nausea, stomach/abdominal pain, dark urine, yellowing eyes/skin), worsening symptoms of heart failure (e.g., ankle/leg swelling, increased tiredness, increased shortness of breath when lying down).

Seek immediate medical attention if any of these unlikely but serious side effects occur: severe dizziness, fainting, sudden change in heartbeat (unusually faster/slower/more irregular), chest pain.

Tell your doctor immediately if any of these rare but very serious side effects occur: seizures, mental/mood changes (e.g., depression, confusion, unusual thoughts/behavior, hallucinations), muscle pain/weakness, dry mouth/eyes.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking procainamide, tell your doctor or pharmacist if you are allergic to it; or to local anesthetics (e.g., procaine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: certain heart problems (second- or third-degree atrioventricular block or bundle branch block unless you have a heart pacemaker), a certain immune problem (lupus).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: first-degree atrioventricular block, new or recent heart attack, worsening chest pain (angina), low blood pressure, kidney problems, liver problems, myasthenia gravis.

Procainamide may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can infrequently result in serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that require immediate medical attention. The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may affect the heart rhythm (see also Drug Interactions section). Before using procainamide, tell your doctor or pharmacist if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using procainamide safely.

Contact your doctor immediately if you develop other illnesses/conditions such as prolonged diarrhea, large quantities of diarrhea, heavy sweating, vomiting, prolonged loss of appetite, or prolonged loss of desire to drink water. These conditions could cause you to have serious changes in blood minerals, leading to increased side effects.

This drug may rarely make you dizzy or drowsy. Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities safely. Limit alcoholic beverages.

Caution is advised when using this drug in the elderly because their bodies may not get rid of procainamide as easily, possibly leading to increased side effects.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk and may have undesirable effects on a nursing infant. Consult your doctor before breast-feeding.