The aim of this review is to describe side effects of five antidementives which 
are approved by the United States Food and Drug Administration (FDA); four 
acetylcholinesterase inhibitors and one glutamate - or N-metyl-D-aspartat 
receptor antagonist - memantine. The antidementives are well tolerated and 
undesired effects are rare; except hepatotoxicity of tacrine and 
gastrointestinal side effects of donepezil, rivastigmine, galantamin and tacrine 
that result from acetylcholinesterase inhibition. Nausea, diarrhea, vomiting, 
and weight loss are the most common side effects of the acetylcholinesterase 
inhibitors. Significant cholinergic side effects can occur in patients receiving 
higher doses; often they are related to the rate of initial titration of 
medication. Memantine is the first noncholinesterase inhibitor indicated for 
Alzheimer's disease. The side effects which may occur during the treatment with 
memantine are constipation, dizziness, headache and confusion. These effects if 
appears are mild end transient.