Norpace 150mg Capsules
WARNING: This drug is only to be used to treat certain types of abnormal heartbeats. Other abnormal heartbeats have happened with this drug, which in rare cases can be deadly. Talk to the doctor if you have any questions about this drug. @ COMMON USES: It is used to treat certain types of abnormal heartbeats.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Antiarrhythmic
Pharmacologic Class
Class Ia Antiarrhythmic (Sodium Channel Blocker)
Pregnancy Category
Category C
FDA Approved
Mar 1977
DEA Schedule
Not Controlled
Overview
What is this medicine?
Disopyramide is a medication used to treat certain types of irregular heartbeats (arrhythmias). It works by affecting the electrical signals in your heart to help it beat more regularly. It can also cause side effects like dry mouth, blurred vision, and difficulty urinating because of its anticholinergic effects.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Continue taking the medication as directed by your doctor or healthcare provider, even if you start to feel better.
If you have difficulty swallowing pills, your doctor or pharmacist can help you prepare a liquid suspension. If a liquid suspension is prepared, make sure to shake it well before each use and measure the dose carefully using the provided measuring device. If no device is included, ask your pharmacist for one to ensure accurate measurement.
Storing and Disposing of Your Medication
Store the medication at room temperature in a dry place, avoiding bathrooms. If a liquid suspension is prepared, store it in the refrigerator, but do not freeze. Discard any unused portion after 30 days.
Keep all medications in a safe location, out of the reach of children and pets, to prevent accidental ingestion or exposure.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Continue taking the medication as directed by your doctor or healthcare provider, even if you start to feel better.
If you have difficulty swallowing pills, your doctor or pharmacist can help you prepare a liquid suspension. If a liquid suspension is prepared, make sure to shake it well before each use and measure the dose carefully using the provided measuring device. If no device is included, ask your pharmacist for one to ensure accurate measurement.
Storing and Disposing of Your Medication
Store the medication at room temperature in a dry place, avoiding bathrooms. If a liquid suspension is prepared, store it in the refrigerator, but do not freeze. Discard any unused portion after 30 days.
Keep all medications in a safe location, out of the reach of children and pets, to prevent accidental ingestion or exposure.
Missing a Dose
If you miss a dose, take it as soon as you remember. However, if it's close to the time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses to make up for the missed one.
Lifestyle & Tips
- Take medication exactly as prescribed, do not skip doses or take extra.
- Avoid grapefruit juice as it can increase drug levels.
- Report any new or worsening symptoms of heart failure (e.g., shortness of breath, swelling, weight gain) immediately.
- Report any new or worsening irregular heartbeats, dizziness, or fainting spells.
- Be aware of anticholinergic side effects like dry mouth (use sugar-free candy/gum), blurred vision (avoid driving if severe), and constipation (increase fiber/fluids).
- Avoid activities requiring mental alertness if experiencing dizziness or blurred vision.
- Do not stop taking this medication suddenly without consulting your doctor.
Available Forms & Alternatives
Available Strengths:
Generic Alternatives:
Dosing & Administration
Adult Dosing
Standard Dose:
150 mg every 6 hours (immediate-release)
Dose Range:
100 - 200 mg
Condition-Specific Dosing:
sustained_ventricular_tachycardia:
200 mg every 6 hours initially, then 150 mg every 6 hours
premature_ventricular_contractions:
100 mg every 6 hours, may increase to 150 mg every 6 hours if needed
cardiomyopathy:
100 mg every 6 hours
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established (limited data, typically 10-30 mg/kg/day divided every 6 hours)
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
CrCl 40-60 mL/min: 100 mg every 8 hours
Moderate:
CrCl 15-40 mL/min: 100 mg every 12 hours
Severe:
CrCl <15 mL/min: 100 mg every 24 hours
Dialysis:
Administer 100 mg after each dialysis session (hemodialysis removes disopyramide)
Hepatic Impairment:
Mild:
No specific adjustment, monitor closely
Moderate:
Reduce dose by approximately 25-50% (e.g., 100 mg every 8 hours or 100 mg every 12 hours), monitor closely
Severe:
Reduce dose by approximately 50% or more (e.g., 100 mg every 12 hours or 100 mg every 24 hours), monitor closely
Pharmacology
Mechanism of Action
Disopyramide is a Class Ia antiarrhythmic agent. It exerts its antiarrhythmic effect by decreasing the rate of depolarization (Phase 0) and prolonging the action potential duration (APD) and effective refractory period (ERP) in atrial and ventricular myocardial fibers and accessory pathways. This is primarily achieved by blocking fast inward sodium channels. It also possesses significant anticholinergic (vagolytic) properties.
Pharmacokinetics
Absorption:
Bioavailability:
80-90%
Tmax:
0.5-3 hours (immediate-release)
FoodEffect:
Food may delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
0.8-1.2 L/kg
ProteinBinding:
50-65% (concentration-dependent, decreases with higher concentrations)
CnssPenetration:
Limited
Elimination:
HalfLife:
4-10 hours (average 6.7 hours)
Clearance:
Not available
ExcretionRoute:
Renal (50-60% unchanged), Hepatic (10-20% as MND)
Unchanged:
50-60%
Pharmacodynamics
OnsetOfAction:
Within 30 minutes (oral)
PeakEffect:
1-3 hours
DurationOfAction:
6-8 hours
Safety & Warnings
BLACK BOX WARNING
MORTALITY. In the National Heart, Lung, and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multicenter, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had myocardial infarction more than six days previously, an excess mortality was observed in patients randomized to encainide or flecainide (Class IC antiarrhythmics) compared with that seen in patients randomized to placebo. The findings of CAST are applicable to other Class I antiarrhythmic drugs, including disopyramide. Therefore, the use of disopyramide should be reserved for patients with life-threatening ventricular arrhythmias.
Side Effects
Serious Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following signs or symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of low blood sugar, including:
+ Dizziness
+ Headache
+ Feeling sleepy
+ Feeling weak
+ Shaking
+ Fast heartbeat
+ Confusion
+ Hunger
+ Sweating
New or worsening abnormal heartbeat
Chest pain or pressure
Changes in eyesight
Trouble passing urine, frequent urination, or urgent need to urinate
Muscle weakness
A type of abnormal heartbeat (prolonged QT interval) has been reported with this medication, which can lead to another type of abnormal heartbeat (torsades de pointes). If you experience a fast or abnormal heartbeat, or if you pass out, contact your doctor right away.
Heart failure has occurred with this medication, as well as worsening heart failure in people with pre-existing heart disease. If you have heart disease, inform your doctor. Seek medical attention immediately if you experience:
+ Shortness of breath
+ Sudden weight gain
+ Abnormal heartbeat
+ New or worsening swelling in the arms or legs
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or may only have mild ones. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical help:
Headache
Constipation
Dry mouth, nose, or throat
Dry eyes
Dizziness
Fatigue
Weakness
Bloating
Gas
Upset stomach
Stomach pain
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following signs or symptoms, contact your doctor or seek medical attention immediately:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Signs of low blood sugar, including:
+ Dizziness
+ Headache
+ Feeling sleepy
+ Feeling weak
+ Shaking
+ Fast heartbeat
+ Confusion
+ Hunger
+ Sweating
New or worsening abnormal heartbeat
Chest pain or pressure
Changes in eyesight
Trouble passing urine, frequent urination, or urgent need to urinate
Muscle weakness
A type of abnormal heartbeat (prolonged QT interval) has been reported with this medication, which can lead to another type of abnormal heartbeat (torsades de pointes). If you experience a fast or abnormal heartbeat, or if you pass out, contact your doctor right away.
Heart failure has occurred with this medication, as well as worsening heart failure in people with pre-existing heart disease. If you have heart disease, inform your doctor. Seek medical attention immediately if you experience:
+ Shortness of breath
+ Sudden weight gain
+ Abnormal heartbeat
+ New or worsening swelling in the arms or legs
Other Possible Side Effects
Like all medications, this drug can cause side effects. Many people may not experience any side effects or may only have mild ones. If you are bothered by any of the following side effects or if they do not go away, contact your doctor or seek medical help:
Headache
Constipation
Dry mouth, nose, or throat
Dry eyes
Dizziness
Fatigue
Weakness
Bloating
Gas
Upset stomach
Stomach pain
This is not an exhaustive list of possible side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- New or worsening irregular heartbeats (palpitations)
- Severe dizziness or lightheadedness
- Fainting spells (syncope)
- Shortness of breath, especially with exertion or lying down
- Swelling in the ankles, feet, or legs
- Sudden weight gain
- Severe dry mouth, difficulty swallowing
- Blurred vision or eye pain
- Difficulty urinating or inability to urinate
- Severe constipation
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reaction you experienced, including the symptoms that occurred.
Certain health conditions, including:
+ Heart problems, such as heart block without a functioning pacemaker, heart failure, a prolonged QT interval on an electrocardiogram (ECG), or low blood pressure.
+ Glaucoma or myasthenia gravis.
+ Urinary retention or difficulty passing urine.
+ Kidney disease.
+ Abnormal potassium levels, either high or low.
+ Recent use of verapamil within the past 24 hours.
This medication can interact with numerous other drugs, which may increase the risk of severe, life-threatening, or fatal side effects. Therefore, it is crucial to discuss the following with your doctor and pharmacist:
All prescription and over-the-counter (OTC) medications you are taking.
Any natural products, vitamins, or supplements you are using.
* Your complete medical history, including all health problems.
Before starting, stopping, or changing the dose of any medication, including this one, you must consult with your doctor to ensure your safety. It is your responsibility to verify that it is safe to take this medication with all your other medications and health conditions.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Describe the allergic reaction you experienced, including the symptoms that occurred.
Certain health conditions, including:
+ Heart problems, such as heart block without a functioning pacemaker, heart failure, a prolonged QT interval on an electrocardiogram (ECG), or low blood pressure.
+ Glaucoma or myasthenia gravis.
+ Urinary retention or difficulty passing urine.
+ Kidney disease.
+ Abnormal potassium levels, either high or low.
+ Recent use of verapamil within the past 24 hours.
This medication can interact with numerous other drugs, which may increase the risk of severe, life-threatening, or fatal side effects. Therefore, it is crucial to discuss the following with your doctor and pharmacist:
All prescription and over-the-counter (OTC) medications you are taking.
Any natural products, vitamins, or supplements you are using.
* Your complete medical history, including all health problems.
Before starting, stopping, or changing the dose of any medication, including this one, you must consult with your doctor to ensure your safety. It is your responsibility to verify that it is safe to take this medication with all your other medications and health conditions.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. In some cases, your doctor may recommend that you start taking this drug in a hospital setting where your condition can be closely monitored.
If you have diabetes, it is crucial to closely monitor your blood sugar levels while taking this medication. Additionally, you should discuss your alcohol consumption with your doctor before drinking.
Elderly patients (65 years and older) should exercise caution when using this drug, as they may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, you must consult your doctor to discuss the potential benefits and risks of this medication to both you and your baby.
If you have diabetes, it is crucial to closely monitor your blood sugar levels while taking this medication. Additionally, you should discuss your alcohol consumption with your doctor before drinking.
Elderly patients (65 years and older) should exercise caution when using this drug, as they may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or are breastfeeding, you must consult your doctor to discuss the potential benefits and risks of this medication to both you and your baby.
Overdose Information
Overdose Symptoms:
- Profound hypotension
- Widening of QRS complex
- Prolongation of QT interval
- Ventricular arrhythmias (e.g., Torsades de Pointes)
- Asystole
- Bradycardia
- Heart block
- Cardiogenic shock
- Respiratory depression
- Coma
- Severe anticholinergic effects (e.g., dilated pupils, hot/dry skin, urinary retention, paralytic ileus, delirium)
What to Do:
Call 911 or Poison Control (1-800-222-1222) immediately. Treatment is supportive and symptomatic. May include gastric lavage, activated charcoal, vasopressors for hypotension, atropine for bradycardia, temporary pacing, IV fluids, correction of electrolyte imbalances (especially potassium and magnesium), and potentially isoproterenol or magnesium for Torsades de Pointes. Hemodialysis may be effective in removing disopyramide.
Drug Interactions
Contraindicated Interactions
- Cisapride
- Dronedarone
- Pimozide
- Thioridazine
- Other drugs known to prolong QT interval (e.g., Class Ia and III antiarrhythmics, certain antipsychotics, macrolide antibiotics, fluoroquinolones) in patients with pre-existing QT prolongation or risk factors.
Major Interactions
- Amiodarone (increased disopyramide levels, increased QT prolongation)
- Beta-blockers (additive negative inotropic effects)
- Calcium channel blockers (e.g., Verapamil, Diltiazem - additive negative inotropic effects, increased disopyramide levels)
- CYP3A4 inhibitors (e.g., Ketoconazole, Itraconazole, Ritonavir, Clarithromycin - increased disopyramide levels)
- CYP3A4 inducers (e.g., Rifampin, Phenytoin, Carbamazepine, Phenobarbital - decreased disopyramide levels)
- Digoxin (increased digoxin levels, additive bradycardia)
- Fingolimod (additive bradycardia)
- Other anticholinergic drugs (e.g., Atropine, TCAs, antihistamines - additive anticholinergic effects)
- QT-prolonging agents (additive QT prolongation, increased risk of Torsades de Pointes)
Moderate Interactions
- Diuretics (especially loop or thiazide - may cause hypokalemia/hypomagnesemia, increasing proarrhythmic risk)
- Grapefruit juice (may inhibit CYP3A4, increasing disopyramide levels)
- Warfarin (potential for increased INR, though not consistently reported)
Minor Interactions
- Antacids (may affect absorption, separate administration)
Monitoring
Baseline Monitoring
Electrocardiogram (ECG)
Rationale: Assess baseline rhythm, PR, QRS, and QTc intervals; identify pre-existing conduction abnormalities or QT prolongation.
Timing: Prior to initiation
Serum Electrolytes (Potassium, Magnesium)
Rationale: Correct hypokalemia or hypomagnesemia prior to therapy to reduce proarrhythmic risk.
Timing: Prior to initiation
Renal Function (CrCl)
Rationale: Disopyramide is primarily renally excreted; dose adjustment is necessary in renal impairment.
Timing: Prior to initiation
Hepatic Function (LFTs)
Rationale: Disopyramide is metabolized by the liver; dose adjustment may be necessary in hepatic impairment.
Timing: Prior to initiation
Blood Pressure
Rationale: Assess baseline and monitor for hypotension.
Timing: Prior to initiation
Symptoms of Heart Failure
Rationale: Disopyramide has negative inotropic effects; assess for signs/symptoms of decompensated heart failure.
Timing: Prior to initiation
Routine Monitoring
Electrocardiogram (ECG)
Frequency: Regularly (e.g., daily during initiation, then weekly/monthly, or with dose changes)
Target: QRS duration <25% increase from baseline, QTc interval <500 ms (or <450 ms in males, <470 ms in females)
Action Threshold: QRS duration increase >25%, QTc >500 ms (or significant prolongation), new arrhythmias, or worsening of existing arrhythmias. Consider dose reduction or discontinuation.
Serum Electrolytes (Potassium, Magnesium)
Frequency: Periodically, especially if on diuretics or with GI losses
Target: Potassium 4.0-5.0 mEq/L, Magnesium 1.8-2.5 mg/dL
Action Threshold: Hypokalemia or hypomagnesemia; correct promptly.
Renal Function (CrCl)
Frequency: Periodically, especially in elderly or those with changing renal function
Target: Stable
Action Threshold: Significant decline in CrCl; adjust dose accordingly.
Disopyramide Plasma Levels (if available/indicated)
Frequency: Periodically, especially with dose changes, suspected toxicity, or lack of efficacy
Target: Therapeutic range: 2-5 mcg/mL
Action Threshold: Levels >5 mcg/mL (increased risk of toxicity) or <2 mcg/mL (potential for subtherapeutic effect); adjust dose.
Blood Pressure
Frequency: Regularly
Target: Stable, within patient's normal range
Action Threshold: Significant hypotension; consider dose reduction or discontinuation.
Symptoms of Heart Failure
Frequency: Ongoing assessment
Target: Absence of new or worsening symptoms
Action Threshold: Development or worsening of dyspnea, edema, weight gain, fatigue; consider discontinuation or alternative therapy.
Anticholinergic Side Effects
Frequency: Ongoing assessment
Target: Tolerable
Action Threshold: Severe dry mouth, blurred vision, urinary retention, constipation; consider dose reduction or alternative therapy.
Symptom Monitoring
- Palpitations
- Dizziness
- Lightheadedness
- Syncope
- Shortness of breath
- Swelling in ankles/feet
- Weight gain
- Dry mouth
- Blurred vision
- Urinary hesitancy or retention
- Constipation
Special Patient Groups
Pregnancy
Category C. Disopyramide crosses the placenta. Use only if the potential benefit justifies the potential risk to the fetus. Has been associated with uterine contractions and premature labor when used in late pregnancy.
Trimester-Specific Risks:
First Trimester:
Limited data, theoretical risk of teratogenicity, but no clear evidence in humans.
Second Trimester:
Potential for fetal bradycardia or arrhythmias. Monitor fetal heart rate.
Third Trimester:
Risk of uterine contractions, premature labor, and neonatal anticholinergic effects (e.g., urinary retention, ileus).
Lactation
L3 (Moderately Safe). Disopyramide is excreted into breast milk. The amount ingested by the infant is relatively small, but potential for anticholinergic effects (e.g., dry mouth, constipation, urinary retention) or cardiac effects in the infant exists. Monitor infant for adverse effects.
Infant Risk:
Low to moderate. Monitor for signs of anticholinergic effects (e.g., constipation, urinary retention, irritability) or cardiac effects (e.g., bradycardia).
Pediatric Use
Safety and efficacy not established in pediatric patients. Use is generally not recommended due to lack of data and potential for serious adverse effects. If used, dosing is highly individualized and requires close monitoring.
Geriatric Use
Elderly patients may be more susceptible to the anticholinergic effects (e.g., urinary retention, constipation, confusion) and negative inotropic effects (heart failure exacerbation) of disopyramide. Renal function often declines with age, necessitating dose adjustments. Start with lower doses and titrate slowly, monitoring closely.
Clinical Information
Clinical Pearls
- Disopyramide is a potent negative inotrope; use with extreme caution or avoid in patients with pre-existing heart failure or significantly impaired left ventricular function.
- Significant anticholinergic side effects are common and can be dose-limiting, especially in elderly men (urinary retention) and patients with glaucoma.
- Always correct hypokalemia and hypomagnesemia before initiating disopyramide to minimize proarrhythmic risk.
- Monitor ECG closely for QRS widening (>25% from baseline) or QTc prolongation (>500 ms), which are signs of toxicity and require dose reduction or discontinuation.
- Due to its narrow therapeutic index and potential for serious adverse effects, disopyramide is generally reserved for life-threatening ventricular arrhythmias when other agents are ineffective or contraindicated, as per its black box warning.
- Consider therapeutic drug monitoring (TDM) for disopyramide levels, especially in patients with renal or hepatic impairment, or when toxicity is suspected.
Alternative Therapies
- Other Class I antiarrhythmics (e.g., Procainamide, Quinidine - though Quinidine also has significant anticholinergic effects and GI side effects)
- Class II antiarrhythmics (Beta-blockers, e.g., Metoprolol, Propranolol)
- Class III antiarrhythmics (e.g., Amiodarone, Sotalol, Dofetilide)
- Class IV antiarrhythmics (Calcium channel blockers, e.g., Verapamil, Diltiazem - for supraventricular arrhythmias)
- Catheter ablation (for certain types of arrhythmias)
Cost & Coverage
Average Cost:
Varies widely, typically $50-$200+ per 100 capsules (100mg or 150mg)
Generic Available:
Yes
Insurance Coverage:
Tier 2 or 3 (often requires prior authorization due to black box warning and alternative therapies)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the medication taken, the amount, and the time it happened.