What is memantine, and how does it work (mechanism of action)?
- Memantine is an oral medication for treating patients with Alzheimer's disease. Other medications used for Alzheimer's disease affect acetylcholine, one of the neurotransmitter chemicals that nerve cells in the brain use to communicate with one another. These drugs – galantamine (Razadyne – formerly known as Reminyl), donezepil (Aricept), rivastigmine (Exelon), and tacrine (Cognex) – inhibit the enzyme acetylcholinesterase that destroys acetylcholine and thereby increase the effects of acetylcholine.
- Memantine's effects are independent of acetylcholine and acetylcholinesterase. Glutamate is the main excitatory neurotransmitter in the brain. It is believed that too much stimulation of nerve cells by glutamate may be responsible for the degeneration of nerves that occurs in some neurological diseases such as Alzheimer's disease.
- Like other neurotransmitters, glutamate is produced and released by nerve cells in the brain. The released glutamate then travels to nearby nerve cells where it attaches to a receptor on the surface of the cells called the N-methyl-D-aspartate (NMDA) receptor. Memantine blocks this receptor and thereby decreases the effects of glutamate. It is thought that by blocking the NMDA receptor and the effects of glutamate, memantine may protect nerve cells from excess stimulation by glutamate.
- Memantine was approved by the FDA in October 2003.
What brand names are available for memantine?
Namenda, Namenda XR
Is memantine available as a generic drug?
Yes.
Do I need a prescription for memantine?
Yes.
What are the uses for memantine?
Memantine is used for the treatment of moderate to
severe dementia associated with Alzheimer’s. Dementia can be categorized into
three levels of severity: mild in which patients are alert and sociable, but
forgetfulness begins to interfere with daily living, moderate which often is the
longest stage of the disease with deterioration of intellect, logic, behavior,
and function, and severe, in which there is loss of long-term memory and
language skills. Patients with severe Alzheimer’s may require 24-hour care and
can no longer complete basic self-care tasks including washing, eating, and
using the bathroom.
What are the side effects of memantine?
The most common side effects of memantine are:
- Increases in blood pressure
- Sleepiness (somnolence)
- Difficulty breathing
Memantine may cause a serious skin reaction called Stevens-Johnson syndrome.
Other potential serious side effects include:
-
Acute
renal failure - Cerebral infarction
- Cerebrovascular accident
- Deep venous thrombosis
- Hepatitis, liver failure
- Intracranial hemorrhage
- Neuroleptic malignant syndrome
- Seizure
- Transient ischemic attack (TIA, mini-stroke)
What is the dosage for memantine?
- The usual starting dose of memantine tablets is 5 mg once
daily. - The dose usually is increased to 5 mg twice daily, then 5 mg and 10 mg as
separate doses daily, and finally 10 mg twice daily. - Memantine can be taken with
or without food. - The initial recommended dose of memantine capsules is 7 mg
daily. - The dose may be increased weekly by 7 mg daily and the maximum dose is 28
mg daily. - Capsules may be swallowed whole or opened and sprinkled on spoonsful
of applesauce. - Capsules should not be crushed or chewed.
Which drugs or supplements interact with memantine?
- Medicines that make the urine more alkaline (for
example, carbonic anhydrase inhibitors such as
acetazolamide (Diamox) and sodium
bicarbonate would be expected to reduce the elimination of memantine by the
kidneys and might increase the blood levels and the risk of side effects of
memantine. - Combining memantine with other NMDA receptor antagonists (for
example,
amantadine
[Symmetrel], ketamine, and dextromethorphan) has not been
evaluated and should be done cautiously.
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Is memantine safe to take if I’m pregnant or breastfeeding?
- Memantine given in high doses to pregnant rats and rabbits
did not affect the offspring. However, studies have not been conducted in
pregnant women. Memantine should only be used during
pregnancy if the potential
benefit justifies the potential risk to the fetus. - It is not known if memantine is excreted into
breast milk.
What else should I know about memantine?
What preparations of memantine are available?
- Tablets: 5 and 10 mg.
- Capsule (extended release): 7, 14,
21 and 28 mg. - Solution: 2 mg/ml.
How should I keep memantine stored?
Tablets should be stored at room temperature, 15 C – 30 C (59 F – 86
F).