Namenda XR 21mg Capsules
It is used to treat dementia in people with Alzheimer's disease.
Drug Class
Agents for Alzheimer's Disease
Pharmacologic Class
N-methyl-D-aspartate (NMDA) Receptor Antagonist
Pregnancy Category
Category B
FDA Approved
Jun 2007
DEA Schedule
Not Controlled
Overview
What is this medicine?
Memantine is a medication used to treat moderate to severe Alzheimer's disease. It works by affecting certain chemicals in the brain that are involved in memory and learning. It may help improve memory, awareness, and the ability to perform daily activities, but it is not a cure for Alzheimer's.
How to Use This Medicine
Taking Your Medication
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food, and continue taking it even if you feel well. It's essential to swallow the capsules whole, without chewing or crushing them. If you notice any damaged or abnormal-looking capsules, do not take them.
If you have difficulty swallowing the capsules whole, you can sprinkle the contents onto applesauce. However, be sure to swallow the mixture immediately without chewing.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless instructed to do so. Instead, consult your pharmacist for guidance on the best disposal method or explore local drug take-back programs.
Missing a Dose
If you miss a dose, skip it and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you miss taking your medication for several days in a row, contact your doctor before restarting your medication regimen.
To use this medication correctly, follow your doctor's instructions and read all the information provided. Take your medication as directed, with or without food, and continue taking it even if you feel well. It's essential to swallow the capsules whole, without chewing or crushing them. If you notice any damaged or abnormal-looking capsules, do not take them.
If you have difficulty swallowing the capsules whole, you can sprinkle the contents onto applesauce. However, be sure to swallow the mixture immediately without chewing.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. When disposing of unused or expired medications, do not flush them down the toilet or pour them down the drain unless instructed to do so. Instead, consult your pharmacist for guidance on the best disposal method or explore local drug take-back programs.
Missing a Dose
If you miss a dose, skip it and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you miss taking your medication for several days in a row, contact your doctor before restarting your medication regimen.
Lifestyle & Tips
- Take the medication exactly as prescribed by your doctor, usually once daily at the same time each day.
- Swallow the capsule whole; do not chew, crush, or divide it. If you have difficulty swallowing, the capsule can be opened and the contents sprinkled on a small amount of applesauce and swallowed immediately without chewing.
- Do not stop taking memantine without consulting your doctor, as symptoms may worsen.
- Maintain regular follow-up appointments with your doctor to monitor your condition and medication effectiveness.
- Report any new or worsening side effects to your healthcare provider.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
Initial: 7 mg once daily. Titrate weekly by 7 mg increments to a target maintenance dose of 28 mg once daily. The 21 mg dose is an intermediate step in titration.
Dose Range:
7 - 28 mg
Condition-Specific Dosing:
moderate_to_severe_alzheimers_disease:
Start with 7 mg once daily, increase to 14 mg once daily in week 2, 21 mg once daily in week 3, and 28 mg once daily in week 4 and thereafter.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Not established
Adolescent:
Not established
Dose Adjustments
Renal Impairment:
Mild:
No dosage adjustment necessary (CrCl 50-80 mL/min).
Moderate:
Dosage should not exceed 14 mg once daily (CrCl 30-49 mL/min).
Severe:
Dosage should not exceed 14 mg once daily (CrCl 5-29 mL/min).
Dialysis:
Not specifically studied, but given severe renal impairment dose reduction, caution is advised. Memantine is minimally dialyzable.
Hepatic Impairment:
Mild:
No dosage adjustment necessary.
Moderate:
No dosage adjustment necessary.
Severe:
Use with caution; dosage adjustment may be necessary but specific recommendations are not available due to limited data.
Pharmacology
Mechanism of Action
Memantine is a low-to-moderate affinity uncompetitive (open-channel) N-methyl-D-aspartate (NMDA) receptor antagonist. It binds to the NMDA receptor-operated cation channels with a higher affinity for the NMDA receptor than for the kainate or AMPA receptors. It is thought to exert its therapeutic effect by blocking the effects of abnormally elevated tonic levels of glutamate, which may contribute to neuronal dysfunction in Alzheimer's disease, without interfering with the physiological activation of NMDA receptors required for normal memory and learning.
Pharmacokinetics
Absorption:
Bioavailability:
Approximately 100%
Tmax:
Approximately 9-12 hours (extended-release)
FoodEffect:
Food does not affect the absorption of memantine extended-release capsules.
Distribution:
Vd:
9-11 L/kg
ProteinBinding:
Approximately 45%
CnssPenetration:
Yes
Elimination:
HalfLife:
Approximately 60-80 hours
Clearance:
105-130 mL/min (renal clearance)
ExcretionRoute:
Primarily renal (approximately 48% to 89% excreted unchanged in urine)
Unchanged:
48-89%
Pharmacodynamics
OnsetOfAction:
Not precisely defined for clinical effect; steady-state concentrations are reached within approximately 7 days.
PeakEffect:
Not precisely defined for clinical effect; clinical benefit is gradual.
DurationOfAction:
Due to long half-life, effects persist for several days after discontinuation.
Confidence:
High
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention, as they may be signs of a severe and potentially life-threatening reaction:
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
Feeling confused
Other Possible Side Effects
While most people may not experience any side effects or only mild ones, it's essential to be aware of the following potential side effects. If you experience any of these or any other side effects that bother you or do not go away, contact your doctor:
Dizziness or headache
Diarrhea or constipation
Important Note: This list is not exhaustive, and you may experience other side effects not mentioned here. If you have any questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention, as they may be signs of a severe and potentially life-threatening reaction:
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
Feeling confused
Other Possible Side Effects
While most people may not experience any side effects or only mild ones, it's essential to be aware of the following potential side effects. If you experience any of these or any other side effects that bother you or do not go away, contact your doctor:
Dizziness or headache
Diarrhea or constipation
Important Note: This list is not exhaustive, and you may experience other side effects not mentioned here. If you have any questions or concerns about side effects, consult 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:
- Severe dizziness or lightheadedness
- Severe headache
- New or worsening confusion or hallucinations
- Difficulty urinating or changes in urine output
- Unusual weakness or tiredness
- Signs of an allergic reaction (rash, itching, swelling, severe dizziness, trouble breathing)
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. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that it is safe to take this medication with all your current medications and health conditions. Do not initiate, discontinue, or modify the dosage of any medication without first consulting 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. Be sure to describe the symptoms you experienced as a result of the allergy.
All medications you are currently taking, including prescription and over-the-counter (OTC) drugs, natural products, and vitamins. This information will help your doctor and pharmacist assess potential interactions between this medication and other substances.
* Any existing health problems, as this medication may interact with certain conditions.
To ensure your safety, it is crucial to verify that it is safe to take this medication with all your current medications and health conditions. Do not initiate, discontinue, or modify the dosage of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all of your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you are pregnant, planning to become pregnant, or are currently breast-feeding, be sure to discuss this with your doctor. This conversation will help you understand the potential benefits and risks of taking this drug, both for you and your baby, allowing you to make an informed decision.
Overdose Information
Overdose Symptoms:
- Severe dizziness
- Agitation
- Confusion
- Hallucinations
- Seizures
- Stupor
- Coma
- Bradycardia
- Respiratory depression
What to Do:
Call 1-800-222-1222 (Poison Control Center) immediately or seek emergency medical attention. Treatment is generally supportive and symptomatic.
Drug Interactions
Moderate Interactions
- Drugs that alkalinize urine (e.g., carbonic anhydrase inhibitors, sodium bicarbonate): May decrease memantine renal clearance, leading to increased plasma levels and potential toxicity.
- NMDA receptor antagonists (e.g., amantadine, ketamine, dextromethorphan): Coadministration may lead to increased incidence or severity of adverse reactions due to additive pharmacodynamic effects.
Monitoring
Baseline Monitoring
Cognitive and functional assessment (e.g., MMSE, ADAS-Cog, ADCS-ADL)
Rationale: To establish baseline disease severity and track progression/response to therapy.
Timing: Prior to initiation of therapy
Renal function (serum creatinine, eGFR/CrCl)
Rationale: To guide initial dosing and subsequent adjustments, especially in patients with impaired renal function.
Timing: Prior to initiation of therapy
Routine Monitoring
Cognitive and functional assessment
Frequency: Every 6-12 months, or as clinically indicated
Target: Improvement or stabilization of symptoms
Action Threshold: Significant decline or lack of benefit may warrant re-evaluation of therapy.
Adverse effects monitoring (e.g., dizziness, headache, confusion, constipation)
Frequency: Regularly, especially during dose titration and initiation
Target: Minimization of side effects
Action Threshold: Persistent or severe adverse effects may require dose reduction or discontinuation.
Renal function (serum creatinine, eGFR/CrCl)
Frequency: Periodically, especially in elderly or those with risk factors for renal impairment
Target: Maintain appropriate dosing based on renal function
Action Threshold: Significant decline in renal function may necessitate dose adjustment.
Symptom Monitoring
- Dizziness
- Headache
- Confusion
- Constipation
- Diarrhea
- Hallucinations
- Hypertension
- Somnolence
- Vomiting
- Agitation
Special Patient Groups
Pregnancy
Memantine is Pregnancy Category B. Animal studies have not shown evidence of teratogenicity, but there are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if clearly needed and the potential benefit outweighs the potential risk to the fetus.
Trimester-Specific Risks:
First Trimester:
No specific increased risk identified in animal studies; human data lacking.
Second Trimester:
No specific increased risk identified in animal studies; human data lacking.
Third Trimester:
No specific increased risk identified in animal studies; human data lacking.
Lactation
It is not known whether memantine is excreted in human milk. Because many drugs are excreted in human milk, and because of the potential for serious adverse reactions in breastfed infants from memantine, 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.
Infant Risk:
L3 (Moderate risk) - No human data; potential for accumulation in infant due to long half-life and potential for CNS effects.
Pediatric Use
Safety and effectiveness in pediatric patients have not been established. Memantine is not indicated for use in pediatric patients.
Geriatric Use
No dosage adjustment is generally required based solely on age. However, elderly patients are more likely to have decreased renal function, which necessitates dosage adjustment based on creatinine clearance.
Clinical Information
Clinical Pearls
- Memantine XR is designed for once-daily dosing, which may improve adherence compared to immediate-release formulations.
- Titration is crucial to minimize side effects and improve tolerability. Do not skip titration steps.
- Patients should be advised to swallow the capsule whole or sprinkle contents on applesauce; crushing or chewing can alter the extended-release properties.
- Monitor for common side effects like dizziness, headache, and confusion, especially during dose escalation.
- Consider potential interactions with drugs that alkalinize urine, as this can increase memantine levels.
- Memantine can be used as monotherapy or in combination with cholinesterase inhibitors for moderate to severe Alzheimer's disease.
Alternative Therapies
- Donepezil (Aricept)
- Rivastigmine (Exelon)
- Galantamine (Razadyne)
Cost & Coverage
Average Cost:
Check current AWP databases (e.g., Red Book, Micromedex) per 30 capsules
Generic Available:
Yes
Insurance Coverage:
Tier 2 or 3 (for brand), Tier 1 (for generic)
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 your medication, don't hesitate to reach out to 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.