Study objective: Avermectins have been used in the control of parasites and insects; however, human data concerning poisoning are lacking. This study investigated the clinical spectrum of avermectin poisoning.
Methods: A retrospective study was conducted to evaluate patients with avermectin poisoning reported to a poison center from September 1993 through December 1997.
Results: Eighteen patients with abamectin (Agri-Mek; 2% wt/wt abamectin) exposure and 1 with ivermectin (Ivomec; 1% wt/vol ivermectin) ingestion were identified. There were 14 male and 5 female patients, ranging in age from 15 to 83 years. Most patients were exposed as a result of attempted suicide (14). Oral ingestion (15) was the most common route of exposure. Four patients were asymptomatic, and 8 had minor symptoms after a mean ingestion of 23 mg/kg abamectin (4.2 to 67 mg/kg), or after dermal and inhalation contact. Seven patients manifested severe symptoms, such as coma (7), aspiration with respiratory failure (4), and hypotension (3), after a mean ingestion of 100.7 mg/kg avermectin (15.4 mg/kg for ivermectin and 114.9 mg/kg for abamectin). All 7 patients received intensive supportive care; 1 patient died 18 days later as a result of multiple organ failure.
Conclusion: Ingestion of a large dose of avermectin may be associated with life-threatening coma, hypotension, and subsequent aspiration.