Strychnine poisoning due to traditional Chinese medicine: a case series

Background: Strychnine poisoning is rare but possibly fatal. The most reported sources of strychnine poisoning include rodenticides and adulterated street heroin. Here we report a case series of an unusual cause of strychnine poisoning - Strychni semen, a herb known as "maqianzi" in traditional Chinese medicine (TCM). Methods: All cases of strychnine poisoning confirmed by the Hospital Authority Toxicology Reference Laboratory (HATRL, the highest-level clinical toxicology laboratory in Hong Kong) between May 2005 and May 2018 were reviewed. Results: Twelve cases of strychnine poisoning were recorded, and Strychni semen was the exclusive source. Ten (83%) patients presented with muscle spasms, and four (33%) developed typical conscious convulsions. The poisoning was severe in two (17%) patients, moderate in three (25%) and mild in eight (58%). No case fatality was recorded. Three (25%) patients were TCM practitioners and two (17%) were laymen who bought the herb themselves without a proper prescription. Conclusion: The practice of TCM is becoming popular in different parts of the world amid the COVID-19 pandemic. The spectrum of clinical features of strychnine poisoning secondary to Strychni semen are similar to those arising from different origins. Eliciting a history of TCM use, apart from exposure to rodenticides and drugs of abuse, may allow timely diagnosis in patients with compatible clinical features. Enhancement of TCM safety could minimize the hazard.