memantine, Namenda, Namenda XR

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GENERIC NAME: memantine

BRAND NAME: Namenda, Namenda XR

DRUG CLASS AND MECHANISM: 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.



PREPARATIONS: Tablets: 5 and 10 mg. Capsule (extended release): 7, 14, 21 and 28 mg. Solution: 2 mg/ml.

STORAGE: Tablets should be stored at room temperature, 15-30 C (59-86 F).

PRESCRIBED FOR: 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.

DOSING: 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.

DRUG INTERACTIONS: 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.

PREGNANCY: 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.

NURSING MOTHERS: It is not known if memantine is excreted into breast milk.

 SIDE EFFECTS: The most common side effects of memantine are fatigue, pain, increases in blood pressure, dizziness, headache, constipation, vomiting, back pain, confusion, somnolence, hallucination, coughing, and difficulty in breathing. Memantine may cause a serious skin reaction called Stevens-Johnson syndrome.

Reference: FDA Prescribing Information

Last Editorial Review: 2/8/2012

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