Systematic Review of Adverse Effects from Herbal Drugs Reported in Randomized Controlled Trials.

Herbal drugs have become a popular form of healthcare, raising concerns about their safety. This study aimed to characterize the adverse effects of herbal drugs through a systematic review of results reported in randomized controlled trials (RCTs). Using eight electronic databases including PubMed, the Cochrane library and six Korean medical databases, the frequency of reported toxicity was recorded based on drug composition and indication. Among 4957 potentially relevant articles, 242 papers comprised of 244 studies met our inclusion criteria; these included 111 studies of a single herb and 133 of multiple herbs. These studies accounted for a total 15 441 participants (male = 5590; female = 9851; 7383 for single and 8058 for multiple herb studies). There were 480 cases (3.1%) of adverse events (344 for single, 136 for multiple herb studies; p < 0.01). A total of 259 cases reported blood test abnormalities, including five cases of abnormality in hepatic functional enzymes. The most frequently reported adverse event was digestive symptoms (44.3%), followed by nervous system symptoms (17.3%) and behaviors such as loss of appetite (16.3%). This is the first systematic review of adverse effects of herbal drugs among clinical studies, and the results indicate that herbal drugs are relatively safe.