Treatment of Alzheimer's disease across the spectrum of severity.

Alzheimer's disease (AD) is the most common cause of dementia affecting nearly 18 million people around the world and 4.5 million in the US. It is a progressive neurodegenerative condition that is estimated to dramatically increase in prevalence as the elderly population continues to grow. As the cognitive and neuropsychiatric signs and symptoms of AD progresses in severity over time, affected individuals become increasingly dependent on others for assistance in performing all activities of daily living. The burden of caring for someone affected by the disorder is great and has substantial impact on a family's emotional, social and financial well-being. In the US, the currently approved medications for the treatment of mild to moderate stages of AD are the cholinesterase inhibitors (ChEIs). Cholinesterase inhibitors have shown modest efficacy in terms of symptomatic improvement and stabilization for periods generally ranging from 6 to 12 months. There are additional data that have emerged, which suggest longer-term benefits. For the moderate to severe stages of AD, memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist is in widespread use and has shown modest benefit as monotherapy and in combination with ChEIs. The cost effectiveness of the currently available therapeutic agents for AD has undergone great scrutiny and remains controversial, especially outside the US. Neuropsychiatric symptoms such as agitation and psychosis are common in AD. Unfortunately, in the US there are no Food and Drug Administration (FDA)-approved agents for the treatment of these symptoms, although atypical antipsychotics have shown some efficacy and have been widely used. However, the use of these agents has recently warranted special caution due to reports of associated adverse effects such as weight gain, hyperlipidemia, glucose intolerance, cerebrovascular events, and an increased risk for death. Alternative agents used to treat neuropsychiatric symptoms include serotonergic antidepressants, benzodiazepines, and anticonvulsant medications.