Dosing and uses of Namenda XR (memantine)
Adult dosage forms and strengths
tablet
- 5mg
- 10mg
capsule, extended-release
- 7mg
- 14mg
- 21mg
- 28mg
oral solution
- 2mg/mL
Alzheimer-Type Dementia
Treatment of moderate-to-severe dementia
Tablet: 5 mg PO once daily initially; increased by increments of 5 mg/day each week; maintenance target dosage (>5 weeks): 20 mg/day PO divided q12hr
Extended-release capsule: 7 mg PO qDay initially; may be increased by increments of 7 mg/day each week; maintenance target dose is 28 mg PO qDay
Dosage modifications
Renal impairment
- Mild or moderate: No dosage adjustment required
- Severe: (CrCl 5-29 mL/min): Not to exceed 14 mg/day (extended-release) or 5 mg BID (prompt-release)
Hepatic impairment
- Mild or moderate (Child Pugh A/B): No dosage adjustment required
- Severe (Child Pugh C): Caution
Administration
May take with or without food
Consume entire capsule contents, do not divide the dose
Swallow capsule whole or open and sprinkle on spoonful of applesauce; do not chew or crush
Do not mix oral solution with any other liquid
Missed dose: Do not double next dose, the next dose should be taken as scheduled; if missed for several days, dosing may need to be resumed at lower doses and retitrated as described above
Mild-to-Moderate Vascular Dementia (Off-label)
5 mg (immediate-release) PO qDay; titrate by 5 mg q7days to target dose 10 mg twice daily
Pediatric dosage forms and strengths
Not indicated
Namenda XR (memantine) adverse (side) effects
1-10%
Dizziness (7%)
Confusion (6%)
Headache (6%)
Constipation (5%)
Cough (4%)
Hypertension (4%)
Backache (3%)
Pain (3%)
Somnolence (3%)
Syncope (3%)
Vomiting (3%)
Dyspnea (2%)
Fatigue (2%)
<1%
Acute renal failure
Cerebral infarction
Cerebrovascular accident
Deep venous thrombosis
Hepatitis, liver failure
Intracranial hemorrhage
Neuroleptic malignant syndrome
Seizure (including grand mal)
Stevens-Johnson syndrome
Transient ischemic attack
Postmarketing Reports
Blood and lymphatic system disorders: Agranulocytosis, leukopenia (including neutropenia), pancytopenia, thrombocytopenia, thrombotic thrombocytopenic purpura
Cardiac disorders: Cardiac failure congestive
Gastrointestinal disorders: Pancreatitis
Hepatobiliary disorders: Hepatitis
Psychiatric disorders: Suicidal ideation
Renal and urinary disorders: Acute renal failure (including increased creatinine and renal insufficiency)
Skin disorders: Stevens Johnson syndrome
Warnings
Contraindications
Hypersensitivity to memantine or components of the formulation
Cautions
Not evaluated in patients with seizure disorder; seizures occurred in 0.2% of patients
Conditions that raise urine pH may decrease urinary elimination and increase plasma levels of memantine
Use caution in cardiovascular disease, seizure disorder, ophthalmic disease, hepatic and/or renal impairment
Pregnancy and lactation
Pregnancy category: B
Lactation: Unknown whether drug is excreted into breast milk; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Namenda XR (memantine)
Mechanism of action
Low- to moderate-affinity uncompetitive N-methyl-D-aspartate (NMDA) receptor (NMDAR) antagonist that binds preferentially to NMDAR-operated cation channels, blocking receptor only under conditions of excessive stimulation, with no effect on normal neurotransmission
Absorption
Peak plasma time: 3-7 hr (immediate release); 9-12 hr (extended release)
Distribution
Protein bound: 45%
Vd: 9-11 L/kg
Metabolism
Metabolites: 3 polar metabolites (minimally active)
Elimination
Half-life: 60-80 hr
Excretion: Urine (74%)
