Namenda and Namenda XR (memantine HCl) Dosage, Side effects, Cost, Drug Interactions | Farah Elzayn, PharmD | RxEconsult
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Namenda XR (memantine HCl) Dosage, Side effects, Cost, Interactions Category: Neurology: Alzheimer's, Dementia, Development by - September 25, 2014 | Views: 17075 | Likes: 1 | Comment: 0  

Namenda for Alzheimer's

Brand Name: Namenda and Namenda XR
Generic Name: memantine HCl 

Medication Class: NMDA receptor antagonist
Similar Drugs: Amantadine (Symmetrel)
Manufacturer: Forest Pharmaceuticals, Inc.
FDA Approval Date: 2003

What is Namenda and how does it work?

Memantine hydrochloride is an oral medication that is used to treat moderate to severe Alzheimer’s disease. It exerts its action through blocking the effect of glutamate. Glutamate is a chemical made by nerve cells in the brain and it may contribute to symptoms associated with Alzheimer’s disease. Glutamate is a stimulatory neurotransmitter in the brain. Scientists think that over stimulation of nerves by glutamate may affect how nerves work in people with Alzheimer's disease. Namenda blocks the receptor that glutamate binds to on nerves, reducing the effect of Namenda. 

What does Namenda treat?

Namenda is used to treat moderate to severe Alzheimer's disease. 

How well does Namenda work?

The efficacy of Namenda was evaluated in two studies in the United States.

In the first study, a total of 252 patients with moderate to severe Alzheimer’s disease participated in the study for a period of 28 weeks. Patients were placed in a group receiving either Namenda or placebo. The Namenda group received 5 mg initially and then the dose was increased weekly by 5 mg increments until a 20 mg per day dose was reached. At 28 weeks cognitive function was assessed using the ADCS-ADL score and the SIB score (Severe Impairment Battery). Both scores use different criteria to assess the functional capabilities of patients.

At 28 weeks, results showed that there was a 3.4 units change in the ADCS-ADL score, and 5.7 units change in the SIB score between the Namenda group and the placebo group. Namenda was shown to be better than placebo.

In the second study, 404 patients with moderate to severe Alzheimer’s disease participated in a 24 weeks study. Patients were placed in a group receiving Namenda plus donepezil or placebo plus donepezil. The Namenda group received an initial dose of 5 mg, and then the dose was increased weekly by 5 mg increments until a 20 mg per day dose was reached.

At 24 weeks, results showed that there was a 1.6 unit change in the ADCS-ADL score and 3.3 units change in the SIB score between the Namenda/donepezil group and the placebo/donepezil group. The Namenda/donepezil group was shown to better than the placebo/donepezil group.

What are some Facts about Namenda?

Namenda does not cure Alzheimer’s disease; it is used to temporarily reduce the symptoms and slow the progression of the disease.

Namenda is also available in extended release tablets which allows for once a day dosing.

The full effect of Namenda might take 4-8 weeks to be observed.

What is the dosage of Namenda?

Namenda is available in 5 mg and 10 mg oral tablets, 7, 14, 21, and 28 mg extended release capsules (Namenda XR), and 2 mg/mL oral solution.

For the treatment of moderate to severe Alzheimer’s disease Namenda is initiated using 5 mg tablets once daily. It can be increased by 5 mg/day weekly. The maximum daily dose of Namenda is 20 mg orally divided every 12 hours.

Extended release capsules are started at 7 mg once daily then increased by 7 mg/day each week up to a target dose of 28 mg once daily. 

What are the side effects of Namenda?

The common side effects associated with Namenda are constipation (5%), diarrhea (5%), vomiting (3%), confusion (6%), dizziness (7%), coughing (4%), and headache (6%)

Serious side effects associated with Namenda are cerebrovascular accident (stroke), seizures, and acute kidney failure.

What are the drug interactions associated with Namenda?

Drugs that cause alkaline (basic) or less acidic urine (e.g., sodium bicarbonate, carbonic anhydrase inhibitors):  

Concomitant use decreases excretion of Namenda by the kidney.

Drugs that are eliminated through the kidneys (e.g., ranitidine, quinidine, cimetidine, nicotine, triamterene):

Concomitant use results in altered excretion of memantine and these agents

What are the warnings and precautions for Namenda?

Namenda increases the risk of cardiovascular disease.

Namenda increases the risk of worsening ophthalmic disease.

Namenda increases the risk of seizures.

The clearance of Namenda is significantly decreased by drugs that cause alkaline urine.

Pregnancy: Namenda is a pregnancy category B; animal studies have shown no fetal risk.

Lactation: The risk of Namenda on infant safety is not known.

What is the cost of Namenda?

The average wholesale price (AWP) for Namenda 5 mg and 10 mg oral tablets is approximately $375 for 60 tablets.

The average wholesale price (AWP) for Namenda 2 mg/mL oral solution is approximately $725 for a 360 mL bottle.

How to obtain prescription assistance for Namenda?

Prescription assistance is available through Forest Pharmaceuticals 

References

Namenda Prescribing Information (Package insert) 

Namenda. Red Book Online. Micromedex 2.0. Truven Health Analytics, Inc. Greenwood Village, CO. Available at www.micromedexsolutions.com.  Accessed September 24, 2014

 



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