Treatment

At present, no treatment can stop Alzheimer's disease. However, some medicines have been able to slow the progression of the disease.

Dietary Supplements

Melatonin

Melatonin is a hormone produced by the pineal gland under the influence of the hypothalamus which receives information from the retina about the daily pattern of light and darkness. The production is inhibited by light and permitted by darkness. Melatonin has been shown to relieve "sundowning" (heightened agitation at late afternoon or evening) associated with Alzheimer's disease (reference).

Melatonin is a potent antioxidant. Since oxidative stress plays a central role in the aging process, melatonin and other antioxidants (e.g., vitamin E) may help prevent Alzheimer's disease.

FDA-Approved Drugs

Cholinesterase Inhibitors

Cholinesterase inhibitors are prescribed for the treatment of mild to moderate AD. They may help delay or prevent symptoms from becoming worse for a limited time and may help control some behavioral symptoms. The medications are: Razadyne?(formerly known as Reminyl? (galantamine), Exelon?(rivastigmine), Aricept?(donepezil), and Cognex?(tacrine).

Cholinesterase is an enzyme that breaks down the neurotransmitter acetylcholine. The use of cholinesterase inhibitors in Alzheimer's disease was originally trying to increase the action of acetylcholine. Later it was found that cholinesterase inhibitors can also reduce the level of beta amyloid (reference).

NMDA Antagonists

The drug approved in this category is Namenda?(memantine), prescribed for the treatment of moderate to severe AD. NMDA (N-methyl D-aspartate) antagonists block a special class of ion channels called NMDA channels which play a critical role in the formation of memory (more info). Opening of NMDA channels allows the entry of calcium ions into the cell. Excessive calcium ions are toxic to the cell. NMDA Antagonists can reduce such toxicity.

Cholesterol-lowering Drugs

Dozens of reports have confirmed that cholesterol-lowering drugs such as statins can reduce the risk of AD.  It was further shown that low cholesterol reduces the production of beta amyloid. The detailed mechanism has also been elucidated (more info).

Anti-inflammatory Drugs

There is evidence that inflammation in the brain may contribute to AD damage. Some studies have suggested that drugs such as nonsteroidal anti-inflammatory drugs (NSAIDs) might help slow the progression of AD, but clinical trials thus far have not demonstrated a benefit from these drugs. A clinical trial studying two of these drugs, rofecoxib (Vioxx) and naproxen (Aleve) showed that they did not delay the progression of AD in people who already have the disease. Another trial, testing whether the NSAIDs celecoxib (Celebrex) and naproxen could prevent AD in healthy older people at risk of the disease, has been suspended.

Drugs Under Development

Target Secretases

Secretases are the enzymes which cleave the amyloid precursor protein (APP) into the toxic beta amyloid. By modifying the way secretases work may reduce the production of beta amyloid. An example is Flurizan (R-flurbiprofen) which is currently in clinical trial.

Block Aggregation of  Beta Amyloid

The toxicity of beta amyloid increases as they clump together. NC-758 is a drug trying to block the aggregation of  beta amyloid. It is currently under phase III clinical trial.

Beta Amyloid Vaccines

Researchers are developing vaccines to mobilize the immune system to fight against beta amyloid. A trial that began in the fall of 2001 was later stopped because inflammation unexpectedly developed in the brains of some of the participants.

Reference:

National Institute on Aging, USA