Uses
Alzheimer’s Disease
Palliative treatment of moderate to severe dementia of the Alzheimer’s type (Alzheimer’s disease).
Dosage and Administration
Administration
Oral Administration
Administer orally without regard to meals.
Administer dosages >5 mg daily in 2 divided doses.
Administer oral solution using the oral dosing syringe and dosing device provided; follow the patient instructions provided by the manufacturer. Do not mix oral solution with any other liquids.
Dosage
Available as memantine hydrochloride; dosage expressed in terms of memantine hydrochloride.
Tablets and oral solution are equivalent on a mg-per-mg basis.
Adults
Alzheimer’s Disease
Oral
Initially, 5 mg once daily for 1 week.
Subsequently, increase dosage to 10 mg daily (5 mg twice daily) for ≥1 week, then 15 mg daily (administered as separate doses of 5 mg and 10 mg) for ≥1 week, and then to 20 mg daily (10 mg twice daily).
Recommended target dosage: 20 mg daily given in 2 divided doses (10 mg twice daily).
Special Populations
Dosage in Hepatic Impairment
No specific dosage recommendations at this time. (See Special Populations under Pharmacokinetics.)
Dosage in Renal Impairment
No dosage adjustment needed in patients with mild to moderate renal impairment. In patients with severe renal impairment (i.e., Clcr 5–29 mL/minute), a target dosage of 5 mg twice daily is recommended. (See Special Populations under Pharmacokinetics.)
Geriatric Patients
No specific dosage adjustments at this time. (See Special Populations under Pharmacokinetics.)
Cautions
Contraindications
- Known hypersensitivity to memantine hydrochloride or any ingredient in the formulation.
Warnings/Precautions
General Precautions
Seizures
Not systematically evaluated in patients with seizure disorders.
Urinary Excretion
Conditions increasing urinary pH (e.g., dietary changes, concomitant use of drugs that alkalinize urine, renal tubular acidosis, severe urinary tract infections) may decrease memantine elimination and increase plasma concentrations and adverse effects; use with caution under these conditions. (See Alkalinizing Agents under Interactions and Elimination under Pharmacokinetics.)
Specific Populations
Pregnancy
Category B.
Lactation
Not known whether memantine is distributed into human milk. Caution if used in nursing women.
Pediatric Use
Safety and efficacy not established.
Geriatric Use
Efficacy studied principally in patients 50–93 (mean 76) years of age with moderate to severe Alzheimer’s disease. (See Special Populations under Pharmacokinetics.)
Hepatic Impairment
Not studied in patients with hepatic impairment. (See Special Populations under Pharmacokinetics.)
Renal Impairment
Increased exposure in patients with renal impairment. (See Renal Impairment under Dosage and Administration and see Special Populations under Pharmacokinetics.)
Common Adverse Effects
Dizziness, confusion, headache, constipation.
Drug Interactions
Minimally metabolized by CYP isoenzymes. Memantine produces minimal inhibition of isoenzymes 1A2, 2A6, 2C9, 2D6, 2E1, or 3A4 in vitro. No induction of isoenzymes 1A2, 2C9, 2E1, or A4/5 observed in vitro at concentrations exceeding those associated with therapeutic efficacy.
Drugs Affecting Hepatic Microsomal Enzymes
Pharmacokinetic interactions unlikely.
Drugs Metabolized by Hepatic Microsomal Enzymes
Pharmacokinetic interactions unlikely.
Alkalinizing Agents
Potential decreased memantine clearance with resulting increases in adverse effects when the drug is used concomitantly with agents that increase urine pH. Use with caution.
Protein-bound Drugs
Pharmacokinetic interaction with highly plasma protein-bound drugs is unlikely because memantine is only 45% bound to plasma proteins.
Drugs Secreted by Renal Tubular Cationic Transport
Potential pharmacokinetic interaction (altered plasma concentrations of both drugs) when used with drugs secreted by the same renal cationic system.
Specific Drugs
| Drug |
Interaction |
Comments |
| Amantadine |
Potential additive NMDA antagonistic effects |
Not systematically evaluated; use caution |
| Carbonic anhydrase inhibitors |
Potential decreased memantine clearance because of alkaline urine; possible increased incidence of adverse effects |
Use with caution |
| Cholinesterase inhibitors (e.g., donepezil, galantamine, tacrine) |
Concomitant use with donepezil has been well tolerated
Reversible inhibition of acetylcholinesterase not affected by memantine in vitro and in animals |
|
| Cimetidine |
Potential altered plasma concentrations of both drugs |
|
| Dextromethorphan |
Potential additive NMDA antagonistic effects |
Not systematically evaluated; use caution |
| Digoxin |
Pharmacokinetic interaction unlikely |
|
| Hydrochlorothiazide (HCTZ) |
Potential altered plasma concentrations of both drugs
Maximum plasma HCTZ concentrations and AUCs decreased by 20% with concomitant use of memantine with fixed-combination of HCTZ and triamterene; memantine bioavailability unaffected |
|
| Ketamine |
Potential additive NMDA antagonistic effects |
Not systematically evaluated; use caution |
| Metformin |
No effect on pharmacokinetics of memantine, metformin, or glyburide with concomitant use of memantine and fixed combination of glyburide and metformin hydrochloride; hypoglycemic effects of glyburide-metformin combination not affected |
|
| Nicotine |
Potential altered plasma concentrations of both drugs |
|
| Quinidine |
Potential altered plasma concentrations of both drugs |
|
| Ranitidine |
Potential altered plasma concentrations of both drugs |
|
| Sodium bicarbonate |
Potential decreased memantine clearance because of alkaline urine; possible increased incidence of adverse effects |
Use with caution |
| Triamterene |
Potential altered plasma concentrations of both drugs
Bioavailability of memantine or triamterene unaffected by concomitant use with triamterene (in fixed-combination with hydrochlorothiazide) |
|
| Warfarin |
Pharmacokinetic interaction unlikely |
|
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