Q&A About Namenda

What is it?

Memantine (Namenda, Forest Labs) is a recently approved treatment for moderate to severe Alzheimer's disease (AD).

Why "moderate to severe" Alzheimer's disease?

Studies of memantine have consistently demonstrated it to be effective in the middle and later stages of AD. By contrast, studies of memantine in "mild to moderate" AD patients have had mixed results.

Should other drugs used to treat AD be stopped before trying memantine?

Cholinesterase-inhibitor drugs (donepezil or Aricept, rivastigmine or Exelon, and galantamine or Reminyl) are approved for treating symptoms of "mild to moderate" AD. One recent study of memantine used in conjunction with donepezil showed the combination to be more effective than donepezil alone.

Other studies have shown that combining memantine with cholinesterase-inhibitor drugs does not significantly increase side effects. These data suggest that combining memantine with a cholinesterase inhibitor drug is appropriate for "moderate" AD patients.

Although memantine is not specifically indicated for use in mild AD patients, and cholinesterase-inhibitors are not approved for use in severe AD, both pose little risk and may, in some circumstances, offer some benefit on an individual basis.

How does memantine work?

The mode of action is thought to involve blocking N-methyl d-aspartate (NMDA) receptors, which are normally activated by the brain chemical glutamate.

In AD, too much or not enough glutamate can have very different effects. Too little glutamate is associated with impaired learning and memory, which is the core clinical feature of AD.

On the other hand, excessive glutamate can trigger a chain of events that leads to the death of brain cells (excitotoxicity). Memantine may moderate the effects of too little or too much glutamate.

Although there is evidence from laboratory studies suggesting that memantine may have a neuroprotective effect in slowing the underlying disease, this has not been proven.

Both memantine and cholinesterase-inhibitor drugs have been shown to slow the rate of clinical or functional decline over time.

In both cases, however, it is not clear if underlying disease processes are being slowed down or not. Slowing clinical decline without altering the overall progression of the disease refers to a symptomatic treatment effect.

How is it dosed?

The recommended dosing of memantine is as follows: 5 mg one/day for one week, then 5 mg twice/day for one week, then 15 mg/day (5/10) for one week, then 20 mg/day (10/10) maintenance dose.

Are there significant side effects or drug interactions?

Memantine has remarkably few side effects overall. Headaches and confusion were reported only to be modestly higher in subjects on memantine + donepezil compared to donepezil only in one large study. No clinically significant drug interactions have been identified to date.

Is it available now?

Yes, many pharmacies stock it now and samples should be available in physician's offices soon.

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