Norpace CR 150mg Capsules
Overview
What is this medicine?
How to Use This Medicine
To get the most benefit from your medication, it's essential to take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. When taking your medication, swallow the tablets whole - do not chew, break, or crush them. Continue taking your medication as prescribed by your doctor or healthcare provider, even if you start to feel better.
Storing and Disposing of Your Medication
To maintain the effectiveness and safety of your medication, store it at room temperature in a dry location, avoiding the bathroom. Keep all medications in a secure place, out of the reach of children and pets. When disposing of unused or expired medication, do not flush it down the toilet or pour it down the drain unless specifically instructed to do so. Instead, consult with your pharmacist for guidance on the best disposal method. You may also want to explore local drug take-back programs for a safe and environmentally friendly way to dispose of your medication.
What to Do If You Miss 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 the medication exactly as prescribed, do not crush, chew, or break the controlled-release capsules.
- Do not stop taking this medication without consulting your doctor, as it can worsen your heart condition.
- Avoid alcohol, as it can worsen side effects or affect the medication's action.
- Be aware of potential side effects like dizziness or blurred vision, and avoid driving or operating machinery until you know how the medication affects you.
- Maintain adequate hydration and fiber intake to help manage anticholinergic side effects like dry mouth and constipation.
- Report any new or worsening symptoms, especially heart-related symptoms, to your doctor immediately.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Condition-Specific Dosing:
Pediatric Dosing
Dose Adjustments
Renal Impairment:
Hepatic Impairment:
Pharmacology
Mechanism of Action
Pharmacokinetics
Absorption:
Distribution:
Elimination:
Pharmacodynamics
Safety & Warnings
BLACK BOX WARNING
Side Effects
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you experience any of the following symptoms, contact your doctor or seek medical help right away:
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 associated with this medication, which can increase the risk of 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 been reported 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. However, many people do not experience any side effects or 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 palpitations
- Dizziness or lightheadedness
- Fainting spells (syncope)
- Shortness of breath
- Swelling in the ankles or feet
- Unusual fatigue or weakness
- Severe dry mouth, blurred vision, difficulty urinating, or severe constipation
Before Using This Medicine
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. Be sure to describe the allergic reaction and its symptoms.
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.
+ Difficulty urinating.
+ 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:
Inform your doctor and pharmacist about all medications you are taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins.
Discuss your health problems with your doctor to ensure it is safe to take this medication.
* Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
If you have diabetes, it is crucial to closely monitor your blood sugar levels while taking this medication. Consult your doctor for guidance on managing your blood sugar.
Before consuming alcohol, discuss the potential risks with your doctor.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. You and your doctor will need 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 tachycardia
- Ventricular fibrillation
- Asystole
- Cardiogenic shock
- Respiratory depression
- Coma
- Anticholinergic effects (e.g., severe dry mouth, dilated pupils, urinary retention, ileus)
What to Do:
Seek immediate medical attention. Call 911 or your local emergency number. For poison control, call 1-800-222-1222. Treatment is supportive and may include gastric lavage, activated charcoal, vasopressors for hypotension, atropine for bradycardia, and correction of electrolyte imbalances. Overdrive pacing or defibrillation may be necessary for severe arrhythmias. Hemodialysis is not effective.
Drug Interactions
Contraindicated Interactions
- Cisapride
- Dronedarone
- Pimozide
- Thioridazine
- Other drugs known to prolong QT interval and cause Torsades de Pointes (unless benefits outweigh risks and close monitoring is possible)
Major Interactions
- Amiodarone (increased disopyramide levels, additive QT prolongation)
- Beta-blockers (additive negative inotropic effects, bradycardia)
- Calcium channel blockers (e.g., Verapamil, Diltiazem - additive negative inotropic effects, bradycardia, AV block)
- Macrolide antibiotics (e.g., Erythromycin, Clarithromycin - CYP3A4 inhibition, increased disopyramide levels, QT prolongation)
- Azole antifungals (e.g., Ketoconazole, Itraconazole - CYP3A4 inhibition, increased disopyramide levels)
- Ritonavir (CYP3A4 inhibition, increased disopyramide levels)
- Phenytoin, Rifampin (CYP3A4 induction, decreased disopyramide levels)
- Other Class Ia antiarrhythmics (additive proarrhythmic effects, QT prolongation)
- Anticholinergic agents (additive anticholinergic effects)
Moderate Interactions
- Digoxin (may increase digoxin levels, additive bradycardia)
- Diuretics (especially loop or thiazide - risk of hypokalemia/hypomagnesemia, increasing proarrhythmia risk)
- Warfarin (potential for increased INR, though not consistently reported)
- Grapefruit juice (CYP3A4 inhibition, potential for increased disopyramide levels)
Minor Interactions
- Antacids (may affect absorption, but generally not clinically significant)
Monitoring
Baseline Monitoring
Rationale: To assess baseline cardiac rhythm, PR, QRS, and QTc intervals, and identify pre-existing conduction abnormalities or prolonged QT.
Timing: Prior to initiation of therapy
Rationale: Hypokalemia and hypomagnesemia can increase the risk of proarrhythmia, especially Torsades de Pointes.
Timing: Prior to initiation of therapy
Rationale: Disopyramide is primarily renally eliminated; dose adjustments are necessary in renal impairment.
Timing: Prior to initiation of therapy
Rationale: Disopyramide is metabolized in the liver; dose adjustments are necessary in hepatic impairment.
Timing: Prior to initiation of therapy
Rationale: To assess baseline hemodynamic status, as disopyramide can cause hypotension.
Timing: Prior to initiation of therapy
Rationale: To assess left ventricular function, as disopyramide has negative inotropic effects and is contraindicated in cardiogenic shock or decompensated heart failure.
Timing: Prior to initiation of therapy, especially in patients with pre-existing heart disease
Routine Monitoring
Frequency: Regularly, especially during dose titration and with changes in clinical status or concomitant medications. At least weekly during initiation, then monthly or quarterly.
Target: Maintain QTc < 450-460 ms (or < 25% increase from baseline); QRS duration < 120 ms (or < 25% increase from baseline)
Action Threshold: Discontinue or reduce dose if QTc prolongs significantly (>500 ms or >25% increase from baseline) or if QRS widens significantly (>25% increase from baseline or >120 ms), or if new arrhythmias occur.
Frequency: During dose titration, with suspected toxicity, or if efficacy is suboptimal. Once stable, periodically.
Target: Therapeutic range: 2-5 mcg/mL (trough)
Action Threshold: Adjust dose to maintain levels within therapeutic range; levels >7 mcg/mL are associated with increased toxicity.
Frequency: Regularly, especially if on diuretics or with GI losses. At least monthly.
Target: Potassium 4.0-5.0 mEq/L; Magnesium 1.8-2.5 mg/dL
Action Threshold: Correct hypokalemia/hypomagnesemia promptly to reduce proarrhythmia risk.
Frequency: Periodically, especially in elderly or those with risk factors for renal impairment. At least every 3-6 months.
Target: Stable within patient's baseline
Action Threshold: Adjust dose if renal function declines.
Frequency: Periodically, especially in those with pre-existing liver disease. At least every 3-6 months.
Target: Stable within patient's baseline
Action Threshold: Adjust dose if hepatic function declines.
Frequency: Regularly, especially during initiation and dose changes.
Target: Within patient's target range
Action Threshold: Manage hypotension if symptomatic or severe.
Symptom Monitoring
- Palpitations
- Dizziness
- Lightheadedness
- Syncope
- Shortness of breath
- Swelling of ankles/feet (signs of heart failure)
- Dry mouth
- Blurred vision
- Urinary retention
- Constipation
- Nausea
- Abdominal pain
- Fatigue
Special Patient Groups
Pregnancy
Disopyramide is Pregnancy Category C. Animal studies have shown adverse effects on the fetus, but there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Trimester-Specific Risks:
Lactation
Disopyramide is excreted into breast milk. The American Academy of Pediatrics considers it to be of 'unknown effect on nursing infant but may be of concern'. Due to potential for serious adverse reactions in the nursing infant (e.g., anticholinergic effects, cardiac effects), a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Use is generally not recommended.
Geriatric Use
Elderly patients may be more susceptible to the anticholinergic effects (e.g., urinary retention, constipation, confusion) and negative inotropic effects of disopyramide. Renal function often declines with age, requiring dose adjustments. Close monitoring of ECG, renal function, and serum levels is crucial.
Clinical Information
Clinical Pearls
- Disopyramide has significant negative inotropic effects; use with extreme caution or avoid in patients with pre-existing heart failure or impaired left ventricular function.
- Its anticholinergic properties are prominent and can lead to bothersome side effects like dry mouth, blurred vision, urinary retention (especially in men with BPH), and constipation.
- Hypokalemia and hypomagnesemia must be corrected prior to and during disopyramide therapy to minimize the risk of proarrhythmia, particularly Torsades de Pointes.
- Therapeutic drug monitoring (serum levels) is recommended due to its narrow therapeutic index and concentration-dependent protein binding.
- Patients should be hospitalized for initiation and significant dose adjustments due to the risk of proarrhythmia and heart failure exacerbation.
- Norpace CR (controlled-release) is designed for twice-daily dosing, improving patient adherence compared to immediate-release formulations.
Alternative Therapies
- Other Class Ia antiarrhythmics (e.g., Procainamide, Quinidine - though less commonly used due to side effects)
- Class Ic antiarrhythmics (e.g., Flecainide, Propafenone - for supraventricular and ventricular arrhythmias in patients without structural heart disease)
- Class III antiarrhythmics (e.g., Amiodarone, Sotalol, Dofetilide - for various arrhythmias, including life-threatening ventricular arrhythmias)
- Beta-blockers (e.g., Metoprolol, Propranolol - for rate control and some antiarrhythmic effects)
- Calcium channel blockers (e.g., Verapamil, Diltiazem - for rate control in supraventricular arrhythmias)
- Catheter ablation (non-pharmacological alternative for certain arrhythmias)