Antihistamines, a possible risk factor for Alzheimer's disease

Antihistamines are frequently administered to psychiatric patients for a variety of purposes. Several large studies of schizophrenics have revealed an extremely high prevalence of Alzheimer's disease neuropathology compared with that in the general population. The neuroleptic treatment of schizophrenia appears to be implicated in this phenomenon. Many of the neuroleptics have anticholinergic effects, some being antihistamines as well, including chlorpromazine. It is proposed here that anticholinergics, including many antihistamines, either exacerbate the Alzheimer process or possibly contribute to its etiology/pathogenesis through their effects on cerebral cholinergic systems. Parsimony in the use of antihistamines thus appears to be warranted both for non-patients and schizophrenics pending the resolution of this issue.