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Memantine side effects and how to avoid them

Memantine side effects include suicidal thoughts, headache, diarrhea, and dizziness
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By | Oct. 26, 2022 Medically reviewed by Anne Jacobson, MD, MPH
Rx pill bottle and prescription pad: Memantine side effects and how to avoid them

Key takeaways

  • Memantine is used to slow the progression of moderate to severe Alzheimer’s disease but cannot stop or reverse it. It works by inhibiting nerve cell death caused by excess glutamate.

  • Common side effects of memantine include headache, diarrhea, dizziness, and confusion, with severe side effects being rare but including heart problems, blood disorders, and suicidal thoughts.

  • Side effects of memantine usually begin early in treatment and are generally temporary, improving over time or upon discontinuation of the drug, with no specific long-term side effects identified from prolonged use.

  • To minimize side effects, it’s recommended to closely follow the prescribed dosage, use a scheduling tool for doses, ensure the healthcare provider is informed of all medications and conditions, and make the living environment safe for those experiencing dizziness or confusion.

In this article:

Memantine is a generic prescription drug used to slow the progress of moderate to severe Alzheimer’s disease. Also prescribed as brand-name Namenda or Namenda XR, memantine inhibits progressive nerve cell death caused by glutamate, a common and necessary chemical in the brain. Glutamate normally attaches to a protein called NMDA at places where nerves meet, but in people with Alzheimer’s, it also attaches to this protein at other parts h2of the nerve cell, causing the cell to die. Memantine selectively blocks the ability of glutamate to do this, so it’s called a selective NMDA receptor antagonist (or inhibitor). Unfortunately, Alzheimer’s is caused by a complex of factors, so memantine can only slow down its progress. It can’t stop or reverse its course. Taken orally as a tablet, extended-release capsule, or oral solution, memantine causes few and fairly mild side effects.

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Common side effects of memantine

In clinical trials, the most common side effects of memantine were headache, diarrhea, and dizziness. But relatively few people experienced these side effects—no more than one in 20 for any single side effect. However, the incidence of side effects was slightly higher in clinical trials for immediate-release memantine than for extended-release memantine. In order of incidence, the most common side effects of memantine are:

  • Headache
  • Diarrhea
  • Dizziness
  • Confusion
  • Flu
  • Anxiety
  • Elevated blood pressure
  • Cough
  • Sleepiness
  • Depression
  • Constipation
  • Vomiting
  • Weight gain
  • Back pain
  • Fatigue
  • Aggressive behavior
  • Hallucinations
  • Shortness of breath
  • Trouble holding urine

Serious side effects of memantine

The most serious side effects of memantine include:

  • Heart problems
  • Blood disorders
  • Suicidal thoughts
  • Kidney failure
  • Swollen pancreas (pancreatitis)
  • Hepatitis
  • A severe skin reaction to the drug 

Memantine and suicidal thoughts

People diagnosed with Alzheimer’s have an increased risk of suicide. The risk is highest among those who are recently diagnosed, are high functioning, or previously made attempts. A normal part of caring for someone with Alzheimer’s is to carefully monitor the person for signs of suicidality such as thinking about suicide, new or worsening depression, or sudden changes in mood or behaviors. These should be immediately reported to the primary healthcare provider or a representative of the residence or nursing facility.

How soon do memantine side effects start?

Many of memantine’s mild side effects can occur early in treatment including headache, dizziness, confusion, and diarrhea. Constipation and weight gain typically take a while to become problems, but the incidence is relatively low. Serious side effects such as a skin reaction called Stevens-Johnson syndrome may take weeks or months of taking a drug to show symptoms.

How long do memantine side effects last?

Many of the side effects of memantine are similar to the symptoms of Alzheimer’s, so it’s not always easy to tell the difference. That being said, the mild side effects of memantine are usually temporary and improve over time. If these problems are too much to tolerate, they usually resolve when the drug is stopped, but it may take some time. With a half-life of two to three days, memantine can linger in the body for a week or more after the last dose is taken.

What are the long-term side effects of memantine?

Memantine is intended to be used for months or years to slow the progress of Alzheimer’s. There are no side effects or health problems specifically caused by long-term use of memantine.

Memantine contraindications

Memantine is never used in people who have had an allergic reaction to memantine.

Pregnancy

Memantine is primarily prescribed to older adults, although it is sometimes used off-label to treat rapid eye movements (nystagmus), a problem that can happen at any age. There is no data concerning the safety of memantine to a developing fetus, though animal studies suggest it may cause developmental problems. The use of memantine during pregnancy is a decision that a woman and her healthcare provider will need to make.

Breastfeeding

Memantine is primarily prescribed to older adults. There is no information about the safety of memantine when given to a mother who is breastfeeding or whether it’s present in breast milk. Treatment with memantine is a decision a woman and her healthcare provider will need to make based on the possible risks and benefits.

Children

Memantine is not FDA-approved for use in children or adolescents. 

Seniors

Alzheimer’s is a disease that primarily affects people older than 65. In clinical trials, there was no difference in effectiveness or adverse effects between people older than 65 and those younger. Healthcare professionals are, however, warned that seniors may be more vulnerable to possible kidney problems when taking memantine.

Memantine warnings

On the whole, memantine is a relatively mild medicine in terms of problems. Not only are side effects not commonly experienced but it doesn’t have a lot of problems with pre-existing conditions, overdose, dependency, or other drugs. Still, there are some warnings that caregivers should be aware of.

Cautions

Only a few pre-existing conditions may require caution or extra monitoring when taking memantine. These include:

  • Severe kidney disease: People with severe kidney disease will not eliminate the drug as well as other people, so lower doses will be prescribed.
  • Alkaline urine: People with a higher-than-normal pH in their urine are dramatically less able to eliminate memantine from the body than people with normal urine. Healthcare providers are advised to be cautious and monitor for side effects in people with medical conditions that can raise urinary pH, such as having severe urinary tract infections or taking medicines that also raise urinary pH. 

Abuse and dependence

Drug abuse and physical dependence are not associated with memantine. There are no rebound or withdrawal symptoms when memantine is discontinued.

Overdose

Call a poison control center or get medical help if too much memantine is taken. Most people will get their memantine dose from a caregiver, so there’s less risk of an overdose than there is with self-medication. Symptoms of an overdose may include:

  • Agitation
  • Restlessness
  • Tiredness
  • Slow heartbeat
  • Confusion
  • Dizziness
  • High blood pressure
  • Lack of energy
  • Stupor
  • Slow movements
  • Passing out
  • Hallucinations
  • Unbalanced walking
  • Vertigo
  • Vomiting
  • Weakness
  • Coma

Memantine interactions

Just as memantine has few side effects and only a few warnings, it also has few drug interactions that are a cause for concern. No drugs are strictly prohibited, but a few might require extra monitoring for side effects. 

The most concerning are drugs that compete with memantine in being filtered by the kidneys. This includes the diabetes drug metformin. When combined with memantine, they can significantly increase memantine levels in the body or memantine can increase their levels. Whatever the effect, the risk of side effects goes up. Healthcare providers will more closely watch for side effects when giving memantine with any of these drugs. 

Some drugs make the urine more alkaline. Simply raising the pH of urine to 8 reduces the elimination of memantine by 80%. That’s a lot, and the risk for side effects goes up accordingly. Healthcare providers are wary about using memantine with drugs that increase the pH of urine. Some of these drugs are well-known, like baking soda (sodium bicarbonate). Others are more obscure but are familiar to the prescriber and the pharmacist.

Some drugs make the urine more acidic. While that doesn’t raise the risk of side effects, it does mean that the body could eliminate memantine more quickly, making it less effective. Again, some of these are familiar like vitamin C. The prescriber and the pharmacist are aware of the others.

Some drugs like the Parkinson’s disease drug amantadine or the cough medicine dextromethorphan produce many of the same side effects as memantine, so side effects can be more frequent and more severe.

How to avoid memantine side effects

Although side effects are relatively uncommon and mild when taking memantine, it still pays to employ a few measures to minimize or avoid possible side effects.

1. Control this medicine

The first and most obvious way to avoid side effects is to make sure the patient is not self-medicating. Memantine is prescribed primarily to people with moderate to severe dementia, so all their medications should be controlled and administered by a caregiver or residence staff. 

RELATED: Alzheimer’s and dementia medication management

2. Follow the instructions when taking this medicine

Give only the dose prescribed following the schedule prescribed. If a dose is missed, it can still be given later unless it’s almost time for the next dose. In that case, skip the missed dose and give the next dose on schedule. 

3. Use a schedule, scheduling app, or alarm to give doses

For people of advanced age with Alzheimer’s, more than one drug is likely being taken. For a caregiver, managing all those doses can be fairly complex. To avoid making mistakes, use a dosing schedule or, better yet, a dosing app on a smartphone or smartwatch. 

RELATED: The 7 best prescription reminder apps and tools

4. Tell the prescriber about all medical conditions

Fortunately, memantine does not cause a lot of issues with pre-existing conditions. However, make sure the prescriber has the patient’s complete medical history including:

  • Any history of seizures
  • Any history of problems passing urine
  • Kidney or bladder problems
  • Liver problems

5. Tell the prescriber about medications and supplements being taken

A few drugs and supplements can cause problems when taken with memantine, so make sure the prescriber knows about all the prescription drugs, over-the-counter medicines, vitamins, and dietary supplements being given to the patient.

6. Keep the prescriber informed about any changes

Any changes in health conditions, prescriptions, or supplements should be communicated to the prescribing healthcare provider.

7. Make the house safe

Making the patient’s residence safe is a priority when taking care of someone with Alzheimer’s. Dizziness, confusion, vertigo, and other effects of memantine are added hazards. The prescribing healthcare professional can provide resources that will help in making living areas safer.

How to treat side effects of memantine

Most of memantine’s side effects are mild, so many can be improved with a few tips.

Drowsiness, dizziness, or unsteadiness

Get the person seated or lying down if they start feeling or acting like they’re dizzy, sleepy, or unsteady on their feet. The goal is to prevent falling, accidents, and injuries. Monitor them carefully and allow them to get up when the dizziness, sleepiness, or other impairment goes away. 

Headaches

Before giving an over-the-counter pain reliever, ask the prescriber if any of these might cause problems. You can use acetaminophen, aspirin, or ibuprofen with memantine, but they may cause problems with other drugs being taken for Alzheimer’s such as Aricept (donepezil). Usually, rest and drinking fluids will help ease the pain. If headaches are severe or don’t go away, get medical advice from the prescriber.

Nausea and vomiting

Give the person water or other fluids to drink frequently, but don’t let them drink too much in one sitting. Just sips. Before giving an antihistamine or other anti-nausea drug, ask the prescriber if it’s okay to take that drug with other medications being given. If vomiting is severe or prolonged, talk to a healthcare professional.

Diarrhea

Make sure the person gets plenty of liquids to prevent dehydration. Water is best. If the diarrhea is severe, watery, bloody, or doesn’t go away, get medical attention.

Skin reactions

Memantine can cause a potentially life-threatening skin reaction called Stevens-Johnson syndrome. It can start with a rash but can quickly develop into a serious problem. Stop giving any drugs and get immediate medical help if symptoms of a skin reaction are noticed. Bring a list of the drugs being taken and their dosages. Symptoms to watch out for include:

  • Skin rash
  • Hives
  • Sores in the mouth
  • Skin blisters
  • Skin peeling
  • Skin pain

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