Memory and cognitive impairments in a case of long-term trihexyphenidyl abuse.

We present a case of long-term trihexyphenidyl (THP) abuse in which memory and cognitive impairments were observed 23 years after the commencement of medication. This case showed a dramatic improvement after withdrawal of THP. Clinical course during admission was followed with psychometric testing and laboratory examinations. The fact that the patient showed no evidence of lowered alertness during the clinical course raises the possibility that THP can primarily induce impairment of memory and cognitive functions. This is supported by the findings on the resting EEG of the patient. This case emphasizes the need to exercise caution in prescribing high doses of anticholinergic agents for long periods, particularly in elderly patients with underlying brain pathology.