Is hyponatremia caused by Chinese herbal medicine a myth? A scoping review and a review of local data in Hong Kong

Abstract

Introduction: Hyponatremia is one of the commonly inquired adverse effects related to Chinese herbal medicine (CHM) received by the Hong Kong Poison Information Center. However, it has never been investigated or reviewed systemically. The purpose of this review is to look into the relationship between CHM and hyponatremia. Method: Databases, including PubMed, the Cochrane library, Embase, and the traditional Chinese medicine database system, were searched for cases reporting hyponatremia after the use of herbs. Inquiries received by the Hong Kong Poison Information Center about CHM-related hyponatremia from 2008 to 2022 July were reviewed retrospectively by two independent doctors (one physician and one clinical toxicologist) using the Adverse Drug Reaction Probability Scale (Naranjo algorithm). Quadratic weighted Kappa was used to test interrater reliability. Results: Three case reports or series about herb-related hyponatremia were identified in the scoping review. Seventy-two patients with hyponatremia and CHM intake were evaluated to determine the possibility of CHM causing hyponatremia. Around 90% of the patients had biochemical profiles compatible with the syndrome of inappropriate secretion of antidiuretic hormones. Most of the patients had a probability likelihood of “possible” as ranked by the Naranjo algorithm. In 19.5% of the hyponatremic patients taking CHM, no other apparent cause was found. Conclusion: The scarcity of literature in scoping review indicates a potential research gap. CHM might be associated with hyponatremia, for which no alternative cause was found. However, meticulous measures must still be made to determine that no other alternative causes are present in a patient with hyponatremia receiving CHM.