Background: Recent studies indicate that the traditional Japanese herbal medicine yi-gan san (YGS, yokukan-san in Japanese) may be safe and useful for treating behavioral and psychological symptoms in dementia, borderline personality disorder, neuroleptic-induced tardive dyskinesia, and treatment-resistant schizophrenia. Visual hallucinations are common and often distressing consequences of vision loss, particularly in age-related macular degeneration. Charles Bonnet syndrome (CBS) is defined by the triad of complex visual hallucinations, ocular pathology causing visual deterioration, and preserved cognitive status. We aimed at evaluating both the efficacy and safety of YGS in patients with CBS.
Methods: Twenty patients diagnosed with CBS were investigated, according to the diagnostic criteria established by Gold and Rabins and Teunisse. Participants were treated in a 4-week open-label study with YGS at an average daily dose of 5.8 ± 2.6 g (2.5-7.5 g). Psychometric instruments used to assess efficacy included the Neuropsychiatric Inventory, hallucination subscale of the Positive and Negative Syndrome Scale, and Clinical Global Impression. No cases of serious adverse events were attributed to the study's drug therapy.
Results: A significant decrease in visual hallucination was observed at 2 and 4 weeks in the Neuropsychiatric Inventory, hallucination subscale of the Positive and Negative Syndrome Scale, and Clinical Global Impression scores.
Conclusions: Yi-gan san may be an effective and safe therapy to control visual hallucination in patients with CBS and should be further tested in double-blind, placebo-controlled trials. Given the design characteristics of this trial, the present findings should be taken cautiously.