Memantine: a therapeutic approach in treating Alzheimer's and vascular dementia.

Memantine has been clinically used in the treatment of organic disorders in Germany for over ten years and has now been approved in Europe and also in the US for moderate to severe Alzheimer's disease. The rationale for this indication is strongly related to the physiological and pathological role of glutamate in neurotransmission. Glutamate is an agonist of NMDA, kainate and AMPA (ionotropic) receptors, where its influence on NMDA receptors plays an important role with regard to neuronal plasticity effecting memory and learning. Excessive levels of glutamate result in neurotoxicity, in part by overactivation of NMDA receptors. Memantine acts as an uncompetitive antagonist of NMDA receptors and therefore compensates for this overactivation. Furthermore, memantine is a neuroprotective agent in various animal models based on both neurodegenerative and vascular processes, as it ameliorates cognitive and memory deficits. Memantine was effective and safe in several clinical studies, particularly in Alzheimer's disease. The compound is completely absorbed after oral intake and undergoes little metabolism. Having a low probability for drug-drug interactions, memantine, in principle, is suited for elderly patients exposed to multiple therapeutic therapies.