In the U.S.—

In Canada—

• Antiarrhythmic

Procainamide ( proe-KANE-a-mide) is used to correct irregular heartbeats to a normal rhythm and to slow an overactive heart. This allows the heart to work more efficiently. Procainamide produces its beneficial effects by slowing nerve impulses in the heart and reducing sensitivity of heart tissues.

Procainamide is available only with your doctor's prescription, in the following dosage forms:

Oral
• Capsules (U.S. and Canada)
• Tablets (U.S.)
• Extended-release tablets (U.S. and Canada)

Parenteral
• Injection (U.S. and Canada)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For procainamide, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to procainamide, procaine, or any other ``caine-type'' medicine. Also tell your health care professional if you are allergic to any other substance, such as foods, preservatives, or dyes.

Pregnancy—Procainamide has not been studied in pregnant women. However, it has been used in some pregnant women and has not been shown to cause problems. Before taking this medicine, make sure your doctor knows if you are pregnant or if you may become pregnant.

Breast-feeding—Procainamide passes into breast milk.

Children—Procainamide has been used in a limited number of children. In effective doses, the medicine has not been shown to cause different side effects or problems than it does in adults.

Older adults—Dizziness or lightheadedness is more likely to occur in the elderly, who are usually more sensitive to the effects of this medicine.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking procainamide, it is especially important that your health care professional know if you are taking any of the following:

• Antiarrhythmics (medicines for heart rhythm problems), other—Effects on the heart may be increased

• Antihypertensives (high blood pressure medicine)—Effects on blood pressure may be increased

• Antimyasthenics (ambenonium [e.g., Mytelase], neostigmine [e.g., Prostigmin], pyridostigmine [e.g., Mestinon])—Effects may be blocked by procainamide

• Pimozide (e.g., Orap)—May increase the risk of heart rhythm problems

• Asthma—Possible allergic reaction

• Kidney disease or
• Liver disease—Effects may be increased because of slower removal of procainamide from the body

• Lupus erythematosus (history of)—Procainamide may cause the condition to become active

• Myasthenia gravis—Procainamide may increase muscle weakness

Take procainamide exactly as directed by your doctor, even though you may feel well. Do not take more medicine than ordered.

Procainamide should be taken with a glass of water on an empty stomach 1 hour before or 2 hours after meals so that it will be absorbed more quickly. However, to lessen stomach upset, your doctor may want you to take the medicine with food or milk.

For patients taking the extended-release tablets:

• Swallow the tablet whole without breaking, crushing, or chewing it.

This medicine works best when there is a constant amount in the blood. To help keep the amount constant, do not miss any doses. Also, it is best to take the doses at evenly spaced times day and night. For example, if you are to take 6 doses a day, the doses should be spaced about 4 hours apart. If this interferes with your sleep or other daily activities, or if you need help in planning the best times to take your medicine, check with your health care professional.

Dosing—

The dose of procainamide will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of procainamide. If your dose is different, do not change it unless your doctor tells you to do so.

The number of capsules or tablets that you take depends on the strength of the medicine.

• For regular (short-acting) oral dosage forms (capsules or tablets):
  • For atrial arrhythmias (fast or irregular heartbeat):
    • Adults—500 milligrams (mg) to 1000 mg (1 gram) every four to six hours.
    • Children—12.5 mg per kilogram (5.68 mg per pound) of body weight four times a day.
  • For ventricular arrhythmias (fast or irregular heartbeat):
    • Adults—50 mg per kilogram (22.73 mg per pound) of body weight per day divided into eight doses taken every three hours.
    • Children—12.5 mg per kilogram (5.68 mg per pound) of body weight four times a day.
• For long-acting oral dosage form (extended-release tablets):
  • For atrial arrhythmias (fast or irregular heartbeat):
    • Adults—1000 mg (1 gram) every six hours.
    • Children—Use is not recommended.
  • For ventricular arrhythmias (fast or irregular heartbeat):
    • Adults—50 mg per kilogram (22.73 mg per pound) of body weight per day divided into four doses taken every six hours.
• For injection dosage form:
  • For arrhythmias (fast or irregular heartbeat):
    • Adults—
      • First few doses: May be given intramuscularly (into the muscle) at 50 mg per kilogram (22.73 mg per pound) of body weight per day in divided doses every three hours; or may be given intravenously (into the vein) by slowly injecting 100 mg (mixed in fluid) every five minutes or infusing 500 to 600 mg (mixed in fluid) over a twenty-five to thirty minute period.
      • Doses after the first few doses: 2 to 6 mg (mixed in fluid) per minute infused into the vein.
    • Children—Dose must be determined by your doctor.

Missed dose—

If you miss a dose of this medicine and remember within 2 hours (4 hours if you are taking the long-acting tablets), take it as soon as possible. However, if you do not remember until later, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, refrigerator, near the kitchen sink, or in other damp places. Moisture usually present in these areas may cause the medicine to break down. Keep the container tightly closed and store in a dry place.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

It is important that your doctor check your progress at regular visits to make sure the medicine is working properly. This will allow necessary changes in the amount of medicine you are taking, which also may help reduce side effects.

Do not stop taking this medicine without first checking with your doctor. Stopping it suddenly may cause a serious change in the activity of your heart. Your doctor may want you to reduce gradually the amount you are taking before stopping completely.

Before having any kind of surgery (including dental surgery) or emergency treatment, tell the medical doctor or dentist in charge that you are taking this medicine.

Your doctor may want you to carry a medical identification card or bracelet stating that you are taking this medicine.

Dizziness or lightheadedness may occur, especially in elderly patients and when large doses are used. Elderly patients should use extra care to avoid falling. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert.

Tell the doctor in charge that you are taking this medicine before you have any medical tests. The results of some tests may be affected by this medicine.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• Less common
  • Fever and chills;  joint pain or swelling ;  pains with breathing;  skin rash or itching 
  
  

• Rare
  • Confusion;  fever or sore mouth, gums, or throat;  hallucinations (seeing, hearing, or feeling things that are not there);  mental depression;  unusual bleeding or bruising;  unusual tiredness or weakness 
  
  

• Signs and symptoms of overdose
  • Confusion;  decrease in urination;  dizziness (severe) or fainting;  drowsiness ;  fast or irregular heartbeat;  nausea and vomiting 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• More common
  • Diarrhea;  loss of appetite 
  
  

• Less common
  • Dizziness or lightheadedness 
  
  

The medicine in the extended-release tablets is contained in a special wax form (matrix). The medicine is slowly released, after which the wax matrix passes out of the body. Sometimes it may be seen in the stool. This is normal and is no cause for concern.

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.