Patients with Alzheimer's disease and vascular dementia are treated for dementia with memantine (Namenda), an inhibitor of NMDA type glutamate receptors.

Memantine Uses:

• Alzheimer disease:

  • Helps with treating a kind of memory loss that's not too severe, linked to a condition called Alzheimer's.

• Off Label Use of Memantine in Adults:

  • Helps with treating a type of memory loss that is not too severe, related to a condition called vascular dementia.

Memantine (Namenda) Dose in Adults:

Memantine (Namenda) Dose in the treatment of moderate to severe Alzheimer disease: Oral:

• Immediate-release:

  • Start with 5 mg once a day.
  • If it's okay for a week, increase to 5 mg twice a day.
  • If that's fine for at least another week, you can increase it again to a maximum of 20 mg per day.
  • If you're taking more than 5 mg per day, divide the doses.
  • If you stop the treatment for a long time, begin with a lower dose and slowly increase it again.
  • Here's a suggested increase plan: 5 mg daily for at least 1 week, then 5 mg twice daily for at least 1 week, followed by 15 mg daily (5 mg and 10 mg in separate doses) for at least 1 week, and finally, 10 mg twice daily.

• Extended-release:

  • Begin with 7 mg once a day. Increase the dose by 7 mg daily, and the highest target dose is 28 mg per day.
  • Allow at least a week to pass before raising the dose again.

Note: When switching from immediate-release to extended-release, start the transition the day after the last immediate-release dose.

You can create a 28 mg extended-release formulation using 10 mg immediate-release tablets.

• Missed dose:

  • If you miss a dose, take the next one as usual.
  • If you've missed doses for a long time, restart with a lower dose and gradually increase it again.

Memantine (Namenda) Dose for treating mild to moderate Vascular dementia (off-label): Oral:

• Immediate release:

  • Start with 5 mg once a day. Increase by 5 mg each week until you reach the target dose of 10 mg twice a day.

Use in Children:

Not recommended or not advised.

Memantine Pregnancy Category: B

• Research on animals has demonstrated negative effects of Memantine.
• Regarding the use of Memantine while breastfeeding, it is uncertain whether the substance is present in breast milk.
• Prior to use by lactating mothers, it is essential to carefully consider the potential risks and benefits.

Memantine (Namenda) Dose in Kidney Disease:

• Mild impairment:
  • No need to change the dosage.
• Moderate impairment:
  • In the United States, no adjustment to the dose is necessary.
  • However, according to Canadian labeling, for individuals with a creatinine clearance (CrCl) between 30 to 49 mL/minute, the initial dose is 5 mg twice daily.
  • If well tolerated for a week, the dose can be increased. After at least a week, the maximum goal dose is 20 mg per day.
• Severe impairment:

  • In the United States, for individuals with creatinine clearance (CrCl) between 5 to 29 mL/minute, the immediate-release dosage starts at 5 mg twice daily.

  • If well tolerated for a week, the dose can be increased, and after at least a week, the maximum goal dose is 14 mg per day.

  • Note that when transitioning from immediate to extended-release, patients on 5 mg twice daily should switch to extended-release 14 mg once daily.

  • In Canada, for individuals with CrCl between 15 to 29 mL/minute, the initial dose is 5 mg once daily for 1 week.

  • If tolerated, it may be increased to 5 mg twice a day.

Memantine Dose in Liver disease:

• For mild-to-moderate impairment, no dose adjustment is necessary.

• In cases of severe impairment, while the manufacturer doesn't recommend a specific dose adjustment, it is not advised to use in instances of severe hepatic impairment.

• It's important to note that, except as mentioned, adverse effects are similar between formulations for immediate and prolonged release.

Less Common Side Effects of Memantine:

• Cardiovascular:

  • Hypotension
  • Hypertension

• Central nervous system:

  • Aggressive behavior
  • Confusion
  • Hallucination
  • Anxiety
  • Drowsiness
  • Pain
  • Headache
  • Fatigue
  • Depression
  • Dizziness

• Endocrine & metabolic:

  • Weight gain

• Gastrointestinal:

  • Vomiting
  • Abdominal pain
  • Constipation
  • Diarrhea

• Genitourinary:

  • Urinary incontinence

• Infection:

  • Influenza

• Neuromuscular & skeletal:

  • Back pain

• Respiratory:

  • Dyspnea
  • Cough

Contraindications to Memantine (Namenda):

Allergic or hypersensitive reactions to memantine or any ingredient in the formulation are contraindications.

If an individual has a known hypersensitivity to memantine or any component of the formulation, the use of this medication is not recommended.

Warnings and precautions

• Hypersensitivity

  • Uncommon cutaneous hypersensitivity reactions, such as Stevens-Johnson syndrome and erythema multiforme, have been reported.
  • It's crucial to be vigilant for signs of a skin rash. If you notice any reaction on the skin, discontinue use immediately.

• Cardiovascular disease

  • There is a low risk of developing cardiotoxicity with this medication.

  • However, an increase in the occurrence of angina, heart failure, hypertension, bradycardia, and cardiac failure has been noted compared to a placebo.

  • It's important to be mindful of the potential for cardiovascular issues while using this medication.

• Hepatic impairment

  • Patients with severe hepatic impairment should exercise caution when using this medication.

  • The Canadian labeling suggests avoiding its use in cases of severe impairment due to a lack of sufficient data.

• Ophthalmic disease

  • Exercise caution if you have any eye problems.

• Renal impairment

  • This substance can be harmful to the kidneys.
  • Adjust the dose based on the clearance of creatinine.

• Seizure disorder

  • Exercise caution when using this medication in cases where seizure disorders have already manifested.

Memantine: Drug Interaction

Monitoring parameters:

• Evaluation of cognitive function and functional outcomes, such as Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs), is important.
• Additionally, periodic eye exams are recommended, as per the Canadian labeling.

How to administer Memantine (Namenda)?

• You can take this medication with or without food.
• Extended-release capsules can be taken whole or broken, but do not chew, crush, or divide them.
• When using the oral solution, use the provided dosing device, and do not mix it with other liquids.
• However, the Canadian labeling suggests that it can be taken with water.

Mechanism of action of Memantine (Namenda):

• In Alzheimer's disease, the major excitatory substance in the brain, glutamate, can overstimulate receptors, leading to harmful effects and nerve cell death.

• Memantine, an antagonist, works by blocking a specific type of glutamate receptor called N-methyl D-aspartate (NMDA).

• In normal situations, magnesium ions block the NMDA receptor channel when it's not stimulated, and they move away when nerve signals stimulate the channel.

• In Alzheimer's, it's theorized that abnormal or excessive activation of these receptors blocks the channel pore, preventing magnesium from entering.

• This results in a continuous open state, allowing too much calcium to enter the nerve cells.

• Memantine helps by acting as a blocker for these receptors.

• It binds to the site usually occupied by magnesium, but only under conditions of excessive stimulation. Importantly, this action doesn't affect normally functioning neurons.

Absorption:

• This medication is easily absorbed by the body.

Protein binding:

• Out of the protein, 45% is stuck or attached to another substance.

Metabolism:

•  

  This substance is mostly not influenced by a specific enzyme system called CYP.

• It works partially in the liver and forms three byproducts, but these byproducts have minimal activity.

Half-life elimination:

• The time it takes for the substance to leave the body completely is approximately between 60 to 80 hours.

Time to peak, serum:

• For the immediate-release form, it takes about 3 to 7 hours for the substance to be fully absorbed and have its effects.
• In the extended-release form, the duration is longer, with effects lasting from 9 to 12 hours.

Excretion:

• Approximately 74% of the substance is eliminated through urine.

• Within this, 48% of the total dosage appears in the urine without undergoing any changes (unchanged drug).

• The elimination process involves active tubular secretion, and reabsorption is enhanced under conditions of alkaline pH.

International Brands of Memantine:

• Namenda
• Namenda Titration Pak
• Namenda XR
• Namenda XR Titration Pack
• ACT Memantine
• APO-Memantine
• Ebixa
• MED-Memantine
• MYLAN-Memantine
• PMSMemantine
• RAN-Memantine
• RATIO-Memantine
• RIVA-Memantine
• SANDOZ Memantine FCT
• SANDOZ Memantine
• Abixa
• Admed
• Admenta
• Akatinol
• Albix
• Alzema
• Amint-10
• Axura
• Carrier
• Cerentia
• Cognitine
• Cordure
• Delmenda
• Dementa
• Denigma
• Ebix
• Ebixa
• Esmirtal
• Eutebrol
• Evy
• Exenta
• Foliant
• Limember
• Lindex
• Manotin
• Mantomed
• Marixino
• Mema
• Memadem-10
• Memanto
• Memanxa
• Memary
• Mementor
• Memogen
• Memora
• Memoria
• Memoril
• Memox
• Memry
• Memxa
• Mentin
• Mentra
• Nemdatine
• Neumantine
• Neuroplus
• Pentabixa
• Remem
• Remtin
• Tabixa
• Vilimen
• Witgen
• Ymana
• Zimerz

Memantine Brand Names in Pakistan: