Common Memantine Side Effects: Treating Alzheimer’s Disease

Memantine hydrochloride (brand names: Namenda, Namenda XR) is used to treat moderate to severe Alzheimer’s disease. But this medicine can also cause some unwanted effects. Please continue reading to find out some of the common side effects of memantine as well as some of the rare but serious side effects of memantine. 

What does memantine do to the brain?

Glutamate is a brain chemical that binds to NMDA (N-methyl-D-aspartate) receptors in the brain. It plays a critical role in memory and learning. While the exact cause of Alzheimer’s disease is not clearly understood, it is believed that too much glutamate can damage the brain, thus contributing to the symptoms of Alzheimer’s disease.  

Memantine belongs to a group of drugs called NMDA receptor antagonists (receptor blockers). Memantine and other drugs in this class bind to NMDA receptors in the central nervous system, where glutamate usually binds. By blocking NMDA receptors, memantine reduces the exposure to glutamate and alleviates the symptoms of Alzheimer’s disease. Keep in mind that memantine works to reduce the symptoms of this brain condition, but it does not cure or slow neurodegeneration in Alzheimer’s patients.

Read about 6 Most Common Medications to Treat Neurological Disorders.

Does memantine really help with dementia?

Memantine is not a cure for Alzheimer’s disease or other types of dementia. But it can help to reduce symptoms such as forgetfulness, confusion, and anxiety. 

Studies have found that 3 out of 4 patients treated with memantine have a positive response and improvement in their symptoms. 

Memantine hydrochloride is generally considered safe and effective for improving symptoms of cognitive and functional decline in people with moderate to severe Alzheimer’s disease. It can be used alone or in combination with other Alzheimer’s medications, such as donepezil. Learn more about donepezil for Alzheimer’s disease.

Find out: What Are The 7 Stages of Dementia?

Save Up To 80% On Alzheimer's Medications With BuzzRx

What are the most common side effects of memantine?

The most common side effects of memantine include dizziness, drowsiness, confusion, headache, constipation, and a general feeling of being unwell. Other side effects of memantine can include:

• Depression

• Aggression

• Unusual tiredness

• Nausea

• Vomiting

• Diarrhea

• Rapid weight gain

• Back pain or pain elsewhere in the body

• Coughing

You should tell your doctor if these side effects are severe or persist after a few days, once your body adjusts to the medicine.

What are the serious adverse effects of memantine?

Some rare but serious adverse effects of memantine can happen. Call your doctor immediately or seek emergency medical help if you experience seizures or sudden changes in mood or behavior. In any case, call 911 if you think you’re experiencing a medical emergency.

Additionally, below are other rare adverse effects that require immediate medical attention. Call your doctor if you develop the symptoms of the following adverse effects: 

• Severe allergic reaction: swelling of the lips, mouth, tongue, or throat, shortness of breath, breathing difficulty, hives, and skin rash. 

• Hepatitis: yellowing of the skin or whites of the eyes, pale stool, or dark-colored urine

• Pancreatitis: sudden, severe stomach pain (in the center of your belly), diarrhea, high fever

• Congestive heart failure and other cardiac issues: fast, pounding, or irregular heartbeat, feeling breathlessness at rest or after exercise, swollen legs and ankles, new persistent cough 

• Acute kidney injury: painful urination, difficulty with urination, cloudy urine, change in urine output, shortness of breath, swelling in legs, ankles, and feet, feeling weakness and fatigue.

• Change in mental status: worsening depression, anxiety, or changes in mood or behavior, hallucinations (seeing or hearing things that are not there)

Call your doctor immediately and seek emergency medical care in case of an overdose of memantine. Overdose symptoms can include dizziness, restlessness, agitation, confusion, trouble concentrating, trouble focusing, sudden severe weakness, swelling of hands and feet, unusual weight gain, low energy, slowed movements, unsteadiness, trouble walking, troubled breathing, twitching of muscles, slowed heartbeat, double vision, sleepiness, vomiting, spinning sensation, hallucinations, and loss of consciousness.

How to reduce the side effects of memantine

Your doctor will start you on a lower dose of memantine and slowly increase the dose. This will help to reduce side effects.

If you develop headaches as a side effect of memantine, it may help to drink plenty of (non-alcoholic) fluids and stay well hydrated. Your healthcare professional may recommend a painkiller. You should call your doctor if your headache is severe or lasts more than a week.

If you develop sleepiness and dizziness after taking memantine, it may be useful to take the medicine in the evening, before bedtime. If you do this, make sure you get up slowly out of bed when using the bathroom at night. If you need to take memantine during the day and it makes you tired, dizzy, or drowsy, do not drive or do any other hazardous activities, such as operating heavy machinery or climbing ladders, until you are fully awake and alert.

If you develop constipation as an adverse effect of memantine, increase fluids and fiber in your diet and get some gentle exercise. Your healthcare professional may prescribe a laxative if your constipation does not go away with lifestyle changes.

Who should not take memantine?

Memantine should be used with caution in people with kidney problems such as renal tubular acidosis or severe urinary tract infections. The urine is alkaline in these conditions (pH 8 or higher). The clearance of memantine is reduced by around 80% when the urine is alkaline. Therefore, an alkaline urine pH can lead to an accumulation of memantine in the body and, consequently, more severe side effects. 

Urine pH can also be affected by diet and drug interactions, for example, with sodium bicarbonate and carbonic anhydrase inhibitors, such as acetazolamide or zonisamide. In addition, memantine should be used with caution in combination with other NMDA antagonists.

Give your doctor a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal remedies, before starting memantine to prevent drug interactions.

What to avoid with memantine

• Do not change the dose or dosing frequency of memantine without talking to your healthcare provider. Memantine comes in regular tablets, extended-release tablets, and oral solutions. Read the prescription label carefully and take your medicine exactly as prescribed.

• Do not skip doses of memantine. This drug can help to control the symptoms of Alzheimer’s but does not cure the condition. If you miss a dose of memantine, take it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose or extra medicine to make up for a missed dose.

• Avoid drinking alcohol while taking memantine. Alcohol can make side effects such as drowsiness and dizziness worse and increase your risk of falls and injuries.

• Do not miss healthcare appointments while on memantine for Alzheimer’s dementia. Your provider may want to adjust the dose of your medicine and monitor you carefully for memantine side effects.