Disopyramide

Disopyramide is a prescription medication used to treat life-threatening abnormal heart rhythms (arrhythmias). This medication belongs to a group of drugs called antiarrhythmics. It works by affecting sodium channels in the heart which slows electrical signals, stabilizing heart rhythm.

Disopyramide comes in capsule form. It is taken 3 to 4 times daily. It is also available in a long-acting form, which is taken twice daily. The long-acting capsules should be swallowed whole.

Common side effects include dry mouth, difficult urination, blurred vision, and dizziness. Do not drive or operate heavy machinery until you know how disopyramide affects you.

Disopyramide is a prescription medications used to treat life-threatening ventricular (lower chambers of the heart) arrhythmias.

These medications may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Disopyramide may be found in some form under the following brand names:

• Norpace

• Norpace CR

Serious side effects have been reported with disopyramide. See the “Disopyramide Precautions” section.

Common side effects include:

• dry mouth
• difficult urination
• constipation
• blurred vision
• dry eyes, nose, and throat
• urinary retention
• frequent urination
• nausea
• bloating and gas pains
• dizziness
• fatigue
• muscle weakness
• headache

This is not a complete list of disopyramide side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

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

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• medications that block a protein in the body (CYP3A4) such as some macrolide antibiotics (clarithromycin, telithromycin), some HIV protease inhibitors (indinavir, nelfinavir, ritonavir, saquinavir), some HCV protease inhibitors (boceprevir, telaprevir), some azole antifungals (ketoconazole, itraconazole, posaconazole, voriconazole), conivaptan (Vaprisol), delavirdine (Rescriptor), and nefazodone
• verapamil
• phenytoin

This is not a complete list of disopyramide drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with disopyramide including the following: 

• Heart Failure/Hypotension. Disopyramide may cause or worsen congestive heart failure or produce severe low blood pressure. Norpace should not be given to patients uncompensated or marginally compensated congestive heart failure or hypotension unless the congestive heart failure or hypotension is secondary to cardiac arrhythmia.
• QRS Widening. Disopyramide may widen the QRS complex. If this happens, your doctor will stop disopyramide. 
• Q-T Prolongation. Disopyramide may cause prolongation of the QT interval. Your doctor will monitor you closely.
• Low blood sugar. Disopyramide may lower blood sugar levels.
• Heart block. If first degree block develops, your doctor will reduce your disopyramide dose. 
• Anticholinergic activity. Disopyramide should not be used in patients with glaucoma, myasthenia gravis, or urinary retention.

Do not take disopyramide if you:

• are allergic to disopyramide or any of its ingredients
• have cardiogenic shock
• have a preexisting second- or third-degree AV block (if no pacemaker is present)
• have congenital Q-T prolongation

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of disopyramide, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking disopyramide, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

• are allergic to disopyramide or any other drugs.
• have or have ever had congestive heart disease, high blood pressure, diabetes, kidney or liver disease, glaucoma, myasthenia gravis, urinary retention, or benign prostatic hypertrophy.
• are pregnant, plan to become pregnant, or are breast-feeding. 
• are having surgery, including dental surgery
• use cigarettes and caffeine-containing beverages. These products may increase the irritability of your heart and interfere with the action of disopyramide.

Disopyramide can make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you. Alcohol can add to the drowsiness caused by this medication.

Talk to your doctor about the risks and benefits of taking disopyramide if you are 65 years of age or older. Older adults should not usually take disopyramide because it is not as safe or effective as other medications that can be used to treat the same condition.

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Disopyramide falls into category C. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

Tell your doctor if you are breastfeeding or plan to breastfeed.

Disopyramide has been detected in human breast milk. Because of the possibility for adverse reactions in nursing infants from disopyramide, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

Take disopyramide exactly as prescribed.

Disopyramide comes in capsule form. It is typically taken 3 to 4 times daily. 

It is also available in a long-acting form, which is taken twice daily. Do not cut, crush, or chew extended-release capsules; swallow them whole.

If you forget a dose, take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

The dosage of disopyramide must be individualized for each patient on the basis of response and tolerance.

The usual adult dosage of disopyramide is 400 to 800 mg per day given in divided doses.

The recommended dosage for most adults is 600 mg/day given in divided doses (300 mg every 12 hours).

For patients whose body weight is less than 110 pounds (50 kg), the recommended dosage is 400 mg/day given in divided doses (200 mg every 12 hours). 

If you take too much disopyramide, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

• Store disopyramide at room temperature.
• Keep this and all medicines out of the reach of children.

Mortality

In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had had a myocardial infarction more than 6 days but less than 2 years previously, an excessive mortality or non-fatal cardiac arrest rate (7.7%) was seen in patients treated with encainide or flecainide compared with that seen in patients assigned to carefully matched placebo-treated groups (3.0%). The average duration of treatment with encainide or flecainide in this study was 10 months.

The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) is uncertain. Considering the known proarrhythmic properties of disopyramide or long-acting disopyramide and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, the use of disopyramide or long-acting disopyramide as well as other antiarrhythmic agents should be reserved for patients with life-threatening ventricular arrhythmias.