Systematic review on the efficacy and safety of herbal medicines for Alzheimer's disease.

A systematic review was conducted to assess the efficacy and safety of herbal medications (HM), as either monotherapy or adjunct to orthodox medications (cholinesterase inhibitors and nootropic agents, OM) for Alzheimer's disease (AD). Sixteen studies testing different HM were included. Out of the 15 HM monotherapy studies, 13 reported HM to be significantly better than OM or placebo; one reported similar efficacy between HM and OM. Only the HM adjuvant study reported significant efficacy. No major adverse events for HM were reported and HMs were found to reduce the adverse effects arising from OM. Imbalance in ethnicity among participants was observed; gender distribution was unclear. Heterogeneity in diagnostic criteria, interventions and outcome measures hindered comprehensive data analysis. Studies comparing HM with OM suggest that HM can be a safe, effective treatment for AD, either alone or in conjunction with OM. Methodological flaws in the design of the studies, however, limited the extent to which the results could be interpreted. Among various HMs, the safety and tolerability of EGb761 was best established. Further multi-center trials with large sample size, high methodological qualities and standardized HM ingredients are necessary for clinical recommendations on the use of HM in treating AD.