Which medicines are used to treat Alzheimer’s disease?
There is no cure for Alzheimer’s disease, but available medications temporarily slow the worsening of dementia symptoms and help with behavioral problems that may appear during the course of the disease.
Four medications representing two drug classes are currently approved by the Food and Drug Administration (FDA) to treat the symptoms of Alzheimer’s disease. These drugs are the cholinesterase inhibitors and a NMDA antagonist.
Cholinesterase inhibitors. The cholinesterase inhibitors are all approved to treat the symptoms of mild to moderate Alzheimer's disease (AD). Cholinesterase inhibitors include:
- Donepezil (Aricept®) (also FDA-approved to treat moderate to severe disease)
- Rivastigmine (Exelon®) and Exelon patch
- Galantamine (Razadyne®)
These drugs work by blocking the action of acetylcholinesterase, the enzyme responsible for destroying acetylcholine. Acetylcholine is one of the chemicals that helps nerve cells communicate. Researchers believe that reduced levels of acetylcholine cause some of the symptoms of Alzheimer's disease. By blocking the enzyme, these medications increase the concentration of acetylcholine in the brain. This increase is believed to help improve some memory problems and reduce some of the behavioral symptoms seen in patients with Alzheimer’s disease.
These medications do not cure Alzheimer’s disease or stop the progression of the disease. The most common side effects of these drugs are nausea, diarrhea, and vomiting. Some people may have loss of appetite, insomnia or bad dreams.
NMDA antagonist. Memantine (Namenda®) is approved by the FDA for treatment of moderate to severe Alzheimer's disease. It blocks the neurotransmitter glutamate from activating NMDA receptors on nerve cells, keeping the cells healthier. This medication works differently than the cholinesterase inhibitors. Memantine can be taken alone or taken together with a cholinesterase inhibitor.
Patients with moderate to severe Alzheimer's who were treated with memantine performed better in studies measuring the common activities of daily living such as eating, walking, toileting, bathing, and dressing compared with patients taking placebo. Patient with lower functioning may benefit the most.
- Summary of medications to treat the symptoms of Alzheimer’s disease. The four current medications approved for Alzheimer’s disease have shown modest effects in preserving brain function. They may help lessen or stabilize the symptom of Alzheimer’s disease for a period of time. Due to the side effects of these drugs – especially the gastrointestinal effects -- doctors and patients should talk about their use before prescribing them. Also, these drugs should be stopped when dementia reaches advanced stages.
Managing behavior changes. Medications are available to treat some of the common behavioral symptoms of Alzheimer’s disease. For example, antidepressant drugs can be used to treat anxiety, restlessness, aggression and depression. Anti-anxiety drugs can be used to treat agitation. Anticonvulsants are sometimes used to treat aggression. Antipsychotics can be used to treat paranoia, hallucinations, and agitation. Some of the side effects of these drugs include confusion and dizziness, which can increase the risk of falls. Therefore these drugs are typically used either for short periods of time, only when behavioral problems are severe, and only after safer and/or other non-drug therapies have been tried first.
What newer medications are under study?
All currently approved medications target Alzheimer’s disease after it develops. Scientists are currently researching ways to stop or slow the progress of Alzheimer’s disease before it starts.
Some of the drugs in late-stage investigation are called monoclonal antibodies. These drugs target the amyloid protein that builds up in brain cells. They work by attaching to the amyloid proteins as they float in the brain and remove them, before they form into the plaques and tangles that interfere with the brain’s ability to properly function.
These drugs are still in clinical trials and are several years away from Food and Drug Administration approval in the United States. Early results have been mixed, with some trials showing no improvement in brain function; others showing a slight improvement (less brain function decline). Despite the mixed results, researchers are excited about this new potential method to modify the disease process.