Most drugs used to treat Alzheimer's, and those under investigation, are aimed at slowing progression. There are no cures to date. In addition, the improvements from some of these drugs may be so modest that patients and their families may not notice benefit.

There are currently two drug classes that have been approved by the U.S. Food and Drug Administration (FDA) to treat the cognitive symptoms of Alzheimer's disease:

- Cholinesterase inhibitors (generally used to treat mild-to-moderate Alzheimer's; donepezil is also approved for treatment of severe dementia )

- N-methyl-D-aspartate (NMDA) receptor antagonists (used to treat moderate-to-severe Alzheimer's)

All of the drugs currently approved for treatment of Alzheimer's disease are expensive. While there are generally no serious risks associated with these medications, these drugs can have a number of bothersome side effects, including indigestion, nausea, vomiting, diarrhea, loss of appetite, muscle cramps, and fatigue.

Patients and caregivers should ask their doctors the following questions about when and if to use these drugs:

- Will there be a noticeable change in behavior or function of the patient? The published studies that enabled approval of these drugs for treatment of Alzheimer's disease demonstrated modest benefit when evaluating patients using cognitive and functional scales. While these scales are important for consistency of recording and performing studies, the benefit demonstrated in these studies does not necessarily translate into any significant clinical benefit in how patients function in their daily lives. There is, in fact, no evidence that use of these medications extends the time before a patient requires care in an institutional setting, such as a nursing home.

- Is it better to use these drugs early in the course of Alzheimer's disease? Treating patients with mild cognitive impairment (persistent mild memory loss of recent events but no diagnosis of Alzheimer's disease) does not seem to prevent patients from developing Alzheimer's disease.