Backgroud: Recent studies indicate that the traditional Japanese herbal medicine yi-gan san (YGS; yokukan-san in Japanese) may be safe and useful in treating behavioral and psychological symptoms in patients with dementia and borderline personality disorder. We aimed at evaluating both the efficacy and safety of YGS in patients with treatment-resistant schizophrenia.
Methods: Thirty-four patients diagnosed with schizophrenia according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, (YGS-free) group (n = 25) and treated in a 4-week open-label study with YGS at an average daily dosage of 6.7 ± 2.5 g (range, 2.5-7.5 g). Psychometric instruments used to assess efficacy included the Positive and Negative Syndrome Scale for Schizophrenia and the Drug-Induced Extrapyramidal Symptom Scale.
Results: A significant decrease was observed at 2 weeks and at 4 weeks in each Positive and Negative Syndrome Scale for Schizophrenia subscale score in the YGS group, but this was not observed in the control group. However, the Drug-Induced Extrapyramidal Symptom Scale total score did not change in both groups.
Conclusions: In this open-label pilot study, patients treated with YGS showed a statistically significant reduction on clinician-rated scales. The present findings suggest that an adjunction of YGS might be effective for treatment-resistant schizophrenia.