Treatment of negative schizophrenic symptoms with trihexyphenidyl

In an effort to investigate reports of possible benefits of trihexyphenidyl on residual schizophrenic symptoms, the drug was administered to five chronic schizophrenic patients with predominantly negative symptoms. These patients were simultaneously receiving various antipsychotic agents without extrapyramidal side effects. There was a marked improvement in four of the five patients, mainly in the areas of affective flattening, anhedonia-asociality, and avolition-apathy. Three of these four patients also reported a reduction in excessive dreaming and nightmares experienced prior to the introduction of trihexyphenidyl. Common pathogenetic mechanisms for negative schizophrenic symptoms and excessive dreaming are discussed. In view of these findings, an investigation of the therapeutic benefits of anticholinergic agents in the treatment of negative schizophrenic symptoms, and the use of decreased dreaming as a possible marker of response, is warranted.