Binds to CNS N-methyl-D-aspartate (NMDA) receptor sites, preventing binding of glutamate, an excitatory neurotransmitter.
Therapeutic effects:
Decreased symptoms of dementia/cognitive decline. Does not slow progression.
Cognitive enhancement.
Pharmacokinetics⬆⬇
Absorption: Well absorbed after oral administration.
Distribution: Unknown.
Metabolism/Excretion: 57–82% excreted unchanged in urine by active tubular secretion moderated by pH dependent tubular reabsorption. Remainder metabolized; metabolites are not pharmacologically active.
Half-Life: 60–80 hr.
Time/Action Profile⬆⬇
(plasma concentrations)
ROUTE
ONSET
PEAK
DURATION
PO
unknown
3–7 hr
12 hr
PO-ER
unknown
9–12 hr
24 hr
Contraind./Precautions⬆⬇
Contraindicated in:
Hypersensitivity.
Use Cautiously in:
Severe renal impairment (↓ dose);
Severe hepatic impairment;
Concurrent use of other NMDA antagonists (amantadine, rimantadine, ketamine, dextromethorphan);
Concurrent use of drugs or diets that cause alkaline urine;
Conditions that ↑ urine pH including severe urinary tract infections or renal tubular acidosis (lead to ↓ excretion and ↑ levels);
OB: Safety not established in pregnancy;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Safety and effectiveness not established in children.
PO (Adults ): Immediate-release: 5 mg once daily initially, ↑ at weekly intervals to 10 mg/day (5 mg twice daily), then 15 mg/day (5 mg once daily, 10 mg once daily as separate doses), then to target dose of 20 mg/day (10 mg twice daily); Extended-release: 7 mg once daily, ↑ at weekly intervals by 7 mg/day to target dose of 28 mg once daily.
Renal Impairment
(Adults ): CCr 5–29 mL/min: Immediate-release (solution): Target dose is 10 mg/day (5 mg twice daily); Extended-release: Target dose is 14 mg once daily.
In combination with: donepezil (Namzaric). See Appendix [not included in this PDA edition].
Assessment⬆⬇
Assess cognitive function (memory, attention, reasoning, language, ability to perform simple tasks) periodically during therapy.
Lab Test Considerations:
May cause anemia.
Implementation⬆⬇
Do not confuse memantine with methadone.
Dose increases should occur no more frequently than weekly.
To switch from immediate release to extended release, patients taking 10 mg twice daily of immediate release tablets may be switched to extended release 28 mg once daily capsules the day following the last dose of a 10 mg immediate release tablet. Patients with renal impairment may use the same procedure to switch from immediate release 5 mg twice daily to extended release 14 mg once daily.
Discontinuation of therapy may result in worsening of cognitive function. Avoid abrupt discontinuation to minimize withdrawal symptoms (altered mental status, hallucinations, delusions, insomnia, increased anxiety, agitation). To taper memantine, use a 50% dose reduction or stepwise reduction via available dose formulations every 4 wks to lowest dose prior to discontinuation. Consider reinitiation if clear worsening of the condition occurs after withdrawal.
PO: May be administered without regard to food.
Administer oral solution using syringe provided. Do not dilute or mix with other fluids. Slowly squirt into corner of patient's mouth.
DNC: Swallow extended release capsules whole; do not crush, chew, or divide. Capsules may be opened, sprinkled on applesauce, and swallowed. Entire contents of each capsule should be consumed; do not divide dose.
Patient/Family Teaching⬆⬇
Instruct patient and caregiver on how and when to administer memantine and how to titrate dose. Take missed doses as soon as remembered but not just before next dose; do not double doses. If several days doses are missed, may need to resume at a lower dose and re-titrate up to previous dose; consult health care professional. Advise patient and caregiver to read Patient Instructions before starting and with each Rx refill in case of changes.
Caution patient and caregiver that memantine may cause dizziness. Monitor and assist with ambulation and caution patient to avoid driving and other activities requiring alertness until response to medication is known.
Advise patient and caregiver to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Teach patient and caregivers that improvement in cognitive functioning may take months; degenerative process is not reversed.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected, or if breastfeeding.
Evaluation/Desired Outcomes⬆⬇
Improvement in neurocognitive decline (memory, attention, reasoning, language, ability to perform simple tasks) in patients with Alzheimer's disease.
