Enkephalin analogue in schizophrenia. Double blind cross-over trial

In a double blind, cross-over study 10 chronic schizophrenic patients with productive symptoms in spite of neuroleptic treatment received the methionine-enkephalin analogue FK 33-824 2 mg i.m. daily for 7 consecutive days. Ratings performed by the Brief Psychiatric Rating Scale did not show any significant differences between FK 33-824 and the active placebo pentobarbital. The clinical condition of one patient worsened during and after the administration of FK 33-824. It is suggested that this might be due to a dopamine stimulating effect. The discrepancy between the findings of the present and a previous open study is discussed. The present study does not support the hypothesis of dysfunction of the endorphin system in schizophrenia.