Ginkgo biloba extract for treatment-resistant schizophrenia.

Forty-two patients with chronic, treatment-resistant schizophrenia who were maintained on optimal doses of clozapine were randomly assigned to receive 120 mg per day of Ginkgo biloba extract (ginkgo; standardized to contain 24% flavone glycosides and 6% terpene lactones) or placebo in addition to clozapine for 12 weeks. The mean percent improvement in negative symptoms (as assessed by the Scale for the Assessment of Negative Symptoms [SANS]) was significantly greater in the ginkgo group than in the placebo group (15.6% vs. 3.5%; p < 0.04). Compared with placebo, ginkgo had no significant effect on positive symptoms or overall psychopathology symptoms.

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Comment: Schizophrenia is a chronic, debilitating disease that frequently fails to respond adequately to antipsychotic medication. Schizophrenia is characterized by a wide array of mental symptoms, which are classified as either "positive" or "negative." The positive symptoms, which include delusions, paranoid thoughts, and hallucinations, frequently respond to treatment with antipsychotic drugs. The negative symptoms, on the other hand, which include blunting of the emotions, social withdrawal, and impairment of cognitive function, often fail to respond to treatment. The results of the present study suggest that ginkgo can enhance the effect of clozapine on negative symptoms in patients with treatment-resistant schizophrenia.

Doruk A et al. A placebo-controlled study of extract of ginkgo bilona added to clozapine in patients with treatment-resistant schizophrenia. Int Clin Psychopharmacol. 2008;23:223-227.

by Alan R. Gaby, MD [e-mail]