Drug consumption in older people is usually high and many prescribed medications have unsuspected anticholinergic (ACH) (Table 1) properties. Drug induced ACH side-effects are particularly severe in aging brain and even more in demented patients. This review will focus on the association between ACH drug intake and the risk of developing central nervous system side-effects in elderly people. The threat of developing cognitive impairment, psychosis and delirium will be particularly analyzed.

Psychosis in Alzheimer's disease is common and troublesome. The impact on the quality of life of both patients and caregivers is high and drug treatments raise concern in terms of both efficacy and safety. Therefore, identifying the risk factors that play an important role in the onset of psychosis is mandatory for the prevention of this clinical condition. From a biological point of view, drugs with anticholinergic properties are a reasonable cause of psychosis. Demented patients have been found to use a disproportionate amount of drugs with anticholinergic properties. On the other hand, new evidence suggests that the cholinergic system may be implicated not only with the onset of cognitive impairment, but even in the genesis of psychosis symptoms. This review focuses on biological and clinical data which suggest that anti-cholinergic drugs should be regarded as a potential risk factor for psychosis in Alzheimer's disease.