Download Namenda (memantine)

Namenda (memantine)
Generic name: Memantine
Available strengths: 5 mg, 10 mg tablets
Available in generic: No
Drug class: Cognitive enhancer/NMDA receptor antagonist
General Information
Namenda (memantine) is a cognitive-enhancing medication for treating moderate-to-severe dementia of
Alzheimer’s disease. Namenda is distinct from the other cognitive enhancers because it represents a new class
of medications with a mechanism of action that is very different from that of other cognitive-enhancing
agents. Namenda works by blocking the receptors for the neurotransmitter glutamate. It is believed that
glutamate plays an important role in the neural pathways associated with learning and memory. In brain disorders such as Alzheimer’s disease, overexcitation of neurons produced by abnormal levels of glutamate may
be associated with neuronal cell dysfunction (resulting in cognitive and memory deficits) and eventual cell
death (leading to deterioration and collapse of intellectual functioning). By selectively blocking a type of
glutamate receptor (NMDA receptor) while allowing for normal neurotransmission, Namenda may help
reduce the excitotoxic effects associated with abnormal transmission of glutamate. In addition, because
Namenda works differently from other cognitive enhancers, it may be combined with other cognitiveenhancing agents such as Aricept. In one short-term (24 weeks) clinical study, patients who took a combination of Namenda and Aricept scored better on measures of cognition, daily activities, and overall functioning
than individuals who took Aricept alone, but the study did not provide data on the long-term benefits of the
combination.
Dosing Information
The starting dosage for Namenda is 5 mg once a day. The dosage is increased in increments of 5 mg/day, separated by a minimum interval of 1 week. After 1 week, for example, the dosage is increased to 5 mg twice a
day (10 mg/day). Dosage adjustments are based on the patient’s response and tolerance to the medication. The
recommended target dosage is 10 mg twice a day (20 mg/day). Patients with impairment of kidney (renal)
function may need lower dosages because renal excretion of Namenda is diminished.
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COGNITIVE ENHANCERS FOR TREATMENT OF ALZHEIMER’S DISEASE
Common Side Effects
Namenda is generally well tolerated. The most frequent side effects reported with Namenda include dizziness, headache, confusion, constipation, sleepiness, fatigue, and general body ache and pain. These adverse
effects were more frequent at the 20-mg/day dosage, but in most cases side effects are usually mild and transient and resolve after 1–3 weeks with continued therapy.
Adverse Reactions and Precautions
In clinical trials, patients receiving Namenda had a higher incidence (4%) of high blood pressure than did
patients who received placebo (2%). It is not clear whether Namenda is associated with a risk of inducing high
blood pressure. Patients should routinely check their blood pressure while taking Namenda.
Namenda is primarily excreted from the body by the kidneys. The excretion of Namenda from the kidneys
may be significantly reduced when the urine is alkaline (basic), which may reduce Namenda clearance by
about 80%. Medical conditions (e.g., urinary tract infections), medications (e.g., Diamox, sodium bicarbonate), or diets that alkalinize urine would be expected to reduce excretion of Namenda from the body, which
may lead to accumulation of the medication and may potentially increase adverse effects.
Namenda is associated with causing dizziness. This is particularly worrisome in seniors who may be susceptible to falling. At the initiation of therapy and at higher dosages, patients and caregivers should be aware
of this potential adverse effect and the risk of falling.
Agitation and aggression were observed with Namenda during clinical trials. Caregivers of patients with
Alzheimer’s disease should keep in mind that aggressive behavior or agitation may not necessarily be symptoms of dementia but may be the result of an adverse effect of the medication. Family members should report
any significant change in the patient’s behavior to his or her physician.
Possible Drug Interactions
Few significant drug interactions are associated with Namenda. Because it is not metabolized extensively by
the liver but excreted primarily by the kidneys unchanged, other medications do not play a significant role in
the metabolism of Namenda. However, medical conditions, medications, or diets that influence the condition
of urine, making it more alkaline, may affect the excretion of Namenda. Medications known as carbonic anhydrase inhibitors, including Diamox (acetazolamide) and Neptazane (methazolamide), prescribed as diuretics
and for treatment of glaucoma, may alkalinize urine and decrease the excretion of Namenda. Sodium bicarbonate, found in baking soda and Alka-Seltzer, is also an alkalinizing agent.
Patients taking Namenda should not consume alcohol because the combination may increase sedation and
drowsiness. Moreover, the sedative effects of alcohol may act as a depressant, obscuring the therapeutic effects
of Namenda and complicating treatment.
Overdose
There are few documented cases of overdose with Namenda, and the information for management of overdose is continually evolving. In a reported case of overdose with 400 mg (forty 10-mg tablets) of Namenda,
the patient experienced restlessness, agitation, psychosis, visual hallucinations, somnolence, stupor, and loss
of consciousness. The patient recovered from the overdose.
Namenda (memantine)
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Any suspected overdose should be treated as an emergency. The person should be taken to the emergency
department for observation and treatment. The prescription bottle of medication (and any other medication
suspected in the overdose) should be brought as well, because the information on the prescription label can
be helpful to the treating physician in determining the number of pills ingested.
Special Considerations
• If you miss a dose, take it as soon as possible, but if it is close to the next scheduled dose, skip the missed
dose and continue on your regular dosing schedule. Do not take double doses.
• Namenda may be taken with or without food. However, it is best to take the medication in the morning
and at bedtime shortly before retiring.
• Prolonged vomiting and diarrhea may result in dehydration and loss of electrolytes, and this can be dangerous, especially for seniors. Inform your physician when prolonged vomiting or diarrhea occurs for more
than 1 day.
• Namenda may cause dizziness and drowsiness, especially during initiation of therapy, and impair your
alertness. Use caution when driving or performing tasks that require alertness.
• Store the medication in its originally labeled, light-resistant container, away from heat and moisture. Heat
and moisture may precipitate breakdown of your medication.
• Keep your medication out of reach of children.
If you have any questions about your medication, consult your physician or pharmacist.
Notes