MEMANTINE

MEMANTINE
(me-man'teen)
Namenda
Classifications: n-methyl-d-aspartate (nmda) receptor antagonist; antidementia agent;
Therapeutic: antidementia agent; nmda receptor antagonist

Pregnancy Category: B

Availability

5 mg, 10 mg tablets; 2 mg/mL solution

Action

Glutamate activation at the (N-methyl-D-aspartate) NMDA receptor is needed for memory and learning processes in the brain. Excess glutamate may play a role in Alzheimer's disease by over-stimulating NMDA receptors, thus causing increased Ca2+ movement into neurons leading to neuronal damage. Memantine is a low-affinity, uncompetitive antagonist at NMDA receptors in the brain. Blockade of NMDA receptors may slow intracellular calcium accumulation, preventing nerve damage without interfering with actions of glutamate that are required for memory and learning.

Therapeutic Effect

Improves cognitive functioning in moderate-to-severe Alzheimer's disease (AD) and in mild-to-moderate vascular dementia.

Uses

Treatment of symptoms of moderate to severe Alzheimer's disease.

Unlabeled Uses

Treatment of moderate to severe vascular dementia.

Contraindications

Renal failure. Safety and efficacy in children are unknown.

Cautious Use

Moderate to severe renal impairment; history of seizure disorder; older adults; concurrent use with carbonic anhydrase inhibitors, or sodium bicarbonate, pregnancy (category B), lactation.

Route & Dosage

Alzheimer's Disease
Adult: PO Initiate with 5 mg once daily, increase dose by 5 mg/wk over a 3-wk period to target dose of 10 mg b.i.d.

Severe Renal Impairment
Decrease to 5 mg b.i.d.

Administration

Oral
  • Note: The recommended interval between dose increases is 1 wk.
  • Dose reductions should be considered with moderate renal impairment.
  • Store between 15°–30° C (59°–86° F).

Adverse Effects (≥1%)

Body as a Whole: Fatigue, pain, flu-like symptoms, peripheral edema. CNS: Dizziness, headache, confusion, somnolence, hallucinations, agitation, insomnia, abnormal gait, depression, anxiety, syncope, TIA, vertigo, ataxia, hypokinesia, aggressive reaction. CV: Hypertension, cardiac failure. GI: Constipation, vomiting, diarrhea, nausea, anorexia. Hematologic: Anemia. Metabolic: Weight loss, increased alkaline phosphatase. Musculoskeletal: Back pain, arthralgia. Respiratory: Coughing, dyspnea, bronchitis, upper respiratory infections, pneumonia. Skin: Rash. Special Senses: Conjunctivitis. Urogenital: Urinary incontinence, UTI, frequent micturition.

Interactions

Drug: Drugs that increase the pH of the urine (CARBONIC ANHYDRASE INIBITORS, sodium bicarbonate) may increase levels of memantine; may enhance the effects of amantadine, dextromethorphan, ketamine, bromocriptine, pergolide, pramipexole, and ropinirole; may enhance the adverse effects of levodopa-containing drugs.

Pharmacokinetics

Absorption: 100% from GI tract. Duration: 4–6 h. Distribution: Easily crosses the blood–brain barrier. Metabolism: Minimal. Elmination: Primarily excreted unchanged in urine. Increases in urinary pH can decrease elimination of drug. Half-Life: 60–80 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor respiratory and CV status, especially with preexisting heart disease.
  • Assess for and report S&S of focal neurologic deficits (e.g., TIA, ataxia, vertigo).
  • Lab tests: Periodic Hct & Hgb, serum sodium, alkaline phosphatase, and blood glucose.
  • Monitor diabetics for loss of glycemic control.

Patient & Family Education

  • Report any of the following to the physician: problems with vision, skin rash, shortness of breath, swelling in throat or tongue, agitation or restlessness, confusion, dizziness, or incontinence.
  • Do not drive or engage in other hazardous activities until reaction to drug is known.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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