Memantine Hcl dosage, forms, and strengths

Memantine is a prescription medication used to slow down the progression of moderate to severe dementia in people with Alzheimer’s disease (AD). It is available in generic form and under the brand name Namenda. Namenda XR formulation has been discontinued from the US market. Memantine belongs to a class of medications called N-methyl-D-aspartate (NMDA) receptor antagonists. It works by blocking a substance in the brain called glutamate, which can help improve memory and thinking. Although memantine can't cure AD or stop it from getting worse, it can help improve how people with Alzheimer's think and remember things, even if just for a while. This can make everyday tasks easier and improve their quality of life.

Sometimes, healthcare providers may prescribe memantine for other conditions not officially approved by the Food and Drug Administration (FDA). This is called off-label use. These include:

• Mild-to-moderate AD

• Vascular dementia (a type of dementia caused by problems with blood flow to the brain)

• Chronic pain

• Certain psychiatric disorders

• Mild cognitive impairment

• Brain metastases (cancer that has spread to the brain), especially in patients who are undergoing radiation therapy

If your healthcare provider prescribes memantine for any of these reasons, they will explain how it may benefit your condition.

Memantine forms and strengths

Memantine is available in several forms, each with its own strengths

• Namenda

• Generic Memantine

They are available as tablet, capsule, or oral solution that you take by mouth:

• Immediate-release tablets: taken twice daily

  • Strengths: 5 mg, 10 mg

• Extended-release capsules: taken once daily 

  • Strengths: 7 mg, 14 mg, 21 mg, 28 mg

• Oral solution: 2 mg/mL (360 mL), also taken by mouth

You can take memantine with or without food but do not chew, crush, or divide the tablets or capsules. If you're using the oral solution, make sure to use the provided syringe and do not mix it with any other liquid. Your healthcare provider will recommend the best form and dose for you.

Memantine dosage for adults

Follows are typical starting, standard, and maximum dosages for memantine.

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Memantine dosage for Alzheimer’s disease

Alzheimer’s has no cure, but drugs can slow the progression of mental decline. Memantine slows the progress of cognitive decline. Memantine is usually combined with a cholinesterase inhibitors. These medications are used to treat dementia symptoms and cognitive issues in people with AD, such as memory loss, confusion, communication problems, and difficulty with organization. Examples of medications in the cholinesterase inhibitor class include Aricept (donepezil), Exelon (rivastigmine), or Razadyne (galantamine). There is a combination capsule containing donepezil and memantine available as a branded product, called Namzaric.

Memantine is taken by mouth daily. Dosages will depend on what formulation is used: immediate-release formulations are given once per day, and extended-release capsules once daily. The dosage typically starts low and gradually increases to a target dose over several weeks.

Immediate-release formulation

• Week 1: 5 mg once per day

• Week 2: 5 mg twice per day

• Week 3: 10 mg in the morning, 5 mg in the evening

• Week 4 (Target Dose): 10 mg twice per day

Standard dosage for moderate-to-severe Alzheimer's Disease (immediate-release):

• 10 mg taken orally twice per day

• Maximum dosage: 20 mg daily

Extended-release formulation

• Week 1: 7 mg once per day

• Week 2: 14 mg once per day

• Week 3: 21 mg once per day

• Week 4 (target dose): 28 mg once per day

Standard dosage for moderate-to-severe Alzheimer's Disease (extended-release):

• 28 mg taken orally once per day

• Maximum dosage: 28 mg daily

Titration packs are available to help organize the dosing schedule, ensuring proper adherence to the prescribed dosage increments.

Memantine dosage for children

Memantine has not been tested for safety or effectiveness in children. It is not approved by the FDA for use in kids. It should not be administered to children without specific guidance from a healthcare provider. 

Memantine dosage restrictions

For individuals with severe renal impairment, the dose must be reduced:

• Immediate-release: 5 mg twice daily

• Extended-release: 14 mg once daily

No dose adjustments are necessary for people with mild kidney disease or hepatic impairment. Still, individuals should be monitored for any side effects such as agitation, confusion, dizziness, vomit, and weakness.

Memantine dosage for pets 

While memantine is not typically used to treat cognitive issues in pets, veterinarians may prescribe memantine to treat compulsive behaviors or chronic pain in dogs. There are no guidelines, but reports have suggested dosages range from 0.3 mg to 1 mg per kilogram of body weight given every 12 hours.

How to take memantine

• Caregivers and/or patients should take memantine exactly as prescribed by the healthcare provider. Do not change the dose.

• Memantine can be taken with or without food.

• Try to take the memantine doses at the same time each day.

• How to administer memantine tablets (immediate-release):

  • Dosage: Memantine is taken twice daily, 12 hours apart.

  • Instructions: Swallow the tablet whole with a glass of water. Do not chew, crush, or break the tablet.

  • Storage: Store at room temperature.

• How to administer memantine oral solution:

  • Dosage: Memantine oral solution is taken twice daily, approximately 12 hours apart. 

  • Measuring the dose: Use the calibrated oral syringe that comes with the medication to measure the correct dose. Do not use kitchen measuring tools (such as spoons or cups), as they may not be accurate. 

  • Titration schedule: When starting memantine oral solution, follow the titration schedule carefully. The dose will gradually increase each week over the course of four weeks. Early doses may involve fractions of a milliliter, so it's important to properly measure fractional doses with the oral syringe. 

  • Storage: Store the oral solution at room temperature. Do not refrigerate or freeze. 

• How to administer memantine extended-release capsules:

  • Dosage: Memantine extended-release capsules are taken once daily.

  • Swallowing the capsule: The patient should swallow the capsule whole with a drink of water. Do not chew or crush the capsule, as it is designed to release the medication slowly. 

  • If swallowing is difficult: If the patient has trouble swallowing the capsule, it can be opened, and the contents can be sprinkled on applesauce. Feed the mixture immediately to the patient. Never split the capsule or take only part of the dose. 

  • Storage: Store memantine extended-release capsules at room temperature.

• How to use memantine titration packs:

  • Titration pack setup: Memantine titration packs come in blister packs with tablets or capsules arranged by week. Start with Week One, and follow the sequence from left to right in the pack.

  • Daily administration: Each week’s pack contains doses for a full week:

  • Week 1: Take one capsule or tablet daily for seven days.

  • Week 2-4: Each pack will have 14 tablets or capsules arranged in two rows: one row for the morning dose (top row) and the other for the evening dose (bottom row).

  • Give the morning dose from the top row and the evening dose from the bottom row.

  • Do not remove tablets early: Do not remove the tablets or capsules from the blister pack until you are ready to give the dose.

  • Storage: Keep the titration packs in the original carton at room temperature to maintain the integrity of the medication.

Memantine dosage FAQs

How long does it take memantine to work?

As mentioned earlier, memantine is not a cure for Alzheimer’s disease, but it can slow the disease. Some people may notice improvements in thinking in the first weeks of treatment, but the disease will still progress at a slower rate. In clinical studies, people taking memantine showed improvement for about four weeks before their condition started to decline again, though more slowly than without the medication. On average, memantine slows progress by about three to four months. Finding the right dose may take a few weeks, starting low to help your body adjust.

How long does memantine stay in your system?

Memantine has a half-life of about 60 to 80 hours. At that rate, it will take about 2-3 weeks for the body to eliminate a dose of memantine completely.

What happens if I miss a dose of memantine?

If you miss a dose, simply skip it and take your next dose at the scheduled time. However, if you miss several doses, it is important to contact your healthcare provider. They may recommend starting at a lower dose and gradually increasing it to the target dose.

How long can you take memantine?

Memantine is intended for long-term use as long as it works and does not cause significant adverse effects. However, as Alzheimer’s is a progressive disease, its long-term benefits remain uncertain although memantine and other AD drugs called cholinesterase inhibitors are clearly beneficial in the short term, there is no certainty about their long-term benefits and no recommendations regarding when it’s time to stop. Decisions regarding the duration of treatment should be made in consultation with the healthcare team, considering the patient's condition and progress. 

How do I stop taking memantine?

Do not stop taking memantine without consulting with your prescribing healthcare provider first. Memantine plays an important role in protecting the brain cells from glutamate overactivity. Your healthcare provider should carefully manage any decision to stop treatment with you. 

Can you overdose on memantine?

An overdose of memantine can be serious. Symptoms of an overdose may include dizziness, agitation, restlessness, confusion, hallucinations, vertigo, weakness, unsteadiness when walking, listlessness, sleepiness, stupor, and, in severe cases, coma. If an overdose is suspected, seek immediate medical attention or contact a poison control center at 800-222-1222. 

What interacts with memantine?

To prevent drug interactions, inform your healthcare provider about all the other prescription drugs, over-the-counter medications, and supplements you are currently taking. Special caution should be taken with:

• Medications that alkalinize the urine, like sodium bicarbonate or carbonic anhydrase inhibitors. When alkalinized, urine can reduce the elimination of these medications, increasing the risk of side effects. 

• Drugs similar to memantine such as amantadine, ketamine, Spravato (esketamine), or dextromethorphan. When combined, it can increase certain side effects such as depression, anxiety, and changes in sleeping patterns. 

What happens when you mix memantine and alcohol?

Alcohol should be avoided while taking memantine, as combining the two may increase side effects such as dizziness and sleepiness. 

Is it safe to take memantine during pregnancy?

Memantine is not recommended during pregnancy. Additionally, it may or may not be safe for breastfeeding women. Its safety during breastfeeding is not well-established or known, as it is unclear whether the drug passes into breast milk, affects lactation, or poses any risk to a nursing infant. 

Sources

• A systematic review and meta-analysis of memantine for the prevention or treatment of chronic pain, European Journal of Pain

• Management of dogs and cats with cognitive dysfunction, Today’s Veterinary Practice

• Use of memantine in treatment of canine compulsive disorders, Journal of Veterinary Behavior

• 2015 AAHA/AAFP Pain management guidelines for dogs and cats, AAHA, (NIH National Library of Medicine)

• Memantine hydrochloride extended-release capsule prescribing information, DailyMed (NIH National Library of Medicine)

• Memantine hydrochloride oral solution prescribing information, DailyMed (NIH National Library of Medicine)

• Memantine hydrochloride tablet prescribing information, DailyMed (NIH National Library of Medicine)

• Radiation therapy for brain metastases: An ASTRO clinical practice guideline, Practical Radiation Oncology

• Withdrawal or continuation of cholinesterase inhibitors or memantine or both, in people with dementia, Cochrane Database of Systematic Reviews

• Memantine in moderate-to-severe Alzheimer’s disease, New England Journal of Medicine