Memantine
Also known as: Namenda, Admenta, Memantia
Important: This is informational content only. Always consult Dr. Ambrish Singal or your psychiatrist before starting, stopping, or changing any medication.
What is Memantine?
Memantine is used for moderate-to-severe Alzheimer's disease. It works differently from cholinesterase inhibitors and can be used alone or in combination with donepezil for enhanced benefit.
How It Works
Non-competitive NMDA receptor antagonist that blocks excessive glutamate activity. In Alzheimer's, overactivation of NMDA receptors by glutamate contributes to neuronal damage. Memantine provides neuroprotection by regulating this activity.
Uses
How This Drug Starts Working
Effects typically begin within 1-4 weeks depending on the condition being treated. Full therapeutic effect usually takes 4-8 weeks.
Week-by-Week Timeline
Week 1: Medication reaching therapeutic blood levels. Some initial side effects may appear as body adjusts.
Week 2-3: Initial therapeutic effects beginning. Side effects often settling.
Week 4-6: Significant therapeutic benefit in most patients.
Week 8+: Full effect established. Treatment response can be properly assessed.
What Changes First?
Physical symptoms (sleep, appetite, energy) typically improve before emotional and cognitive symptoms. Others may notice improvement before you feel it yourself.
Why Does It Take Time?
Psychiatric medications work by gradually rebalancing brain chemistry and neural circuits. Unlike pain medications that block a sensation, these drugs help your brain rebuild healthy patterns — which requires time.
Complete Dosage Guide
How to Take
Take exactly as prescribed by your doctor. Maintain consistent timing each day.
Starting Dose
Your doctor will determine the appropriate starting dose based on your condition, age, weight, and other factors.
Dose Increases
Dose adjustments are made gradually based on your response and side effects. Follow your doctor's instructions for any changes.
Maximum Dose
Your doctor will not exceed safe maximum doses. Never take more than prescribed.
When to Take
Take at the same time daily for best results. Ask your doctor whether morning or evening is better for your specific medication.
If You Miss a Dose
If you miss a dose, take it as soon as you remember unless close to your next dose. Never double up. Contact your doctor if you miss multiple doses.
Food & Drink
Ask your doctor or pharmacist about specific food interactions for your medication.
How Long to Take
Duration of treatment varies by condition. Never stop medication without discussing with your doctor first — some medications require gradual tapering.
Dosage by Age Group
adult
Start 5mg once daily. Increase by 5mg/week: Week 2: 5mg twice daily. Week 3: 10mg+5mg. Week 4 target: 10mg twice daily.
child
Not used in children.
elderly
Standard dosing. Most patients are elderly.
Special Populations
Pregnancy
Category B. Not typically relevant.
Kidney Conditions
Reduce dose to 5mg twice daily if CrCl 5-29 mL/min.
Liver Conditions
Use with caution in moderate-severe hepatic impairment. Limited data.
Side Effects
Common
- Dizziness
- Headache
- Constipation
- Confusion
- Fatigue
Serious
- Hallucinations
- Seizures (rare)
- Heart failure (rare)
- Stevens-Johnson Syndrome (very rare)
What You Should Know
Overdose Risks
Symptoms include restlessness, psychosis, visual hallucinations, somnolence, and stupor. Generally manageable with supportive care.
Safe Discontinuation
Can be stopped without tapering. Cognitive decline may accelerate after discontinuation.