Acute Poisoning with a Herbicide Containing Imazapyr (Arsenal): A Report of Six Cases

Abstract

Background: Acute pesticide poisoning is a major cause of morbidity and mortality in Taiwan and herbicides are most frequently implicated. Imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2 imidazoline-2-yl)nicotinic acid] is a new herbicide, recently registered in Taiwan under the tradename “Arsenal” (Imazapyr 23.1%, Cyanamid Taiwan Corporation, Taipei). Imazapyr is also marketed as Assault, Chopper, Contain, and Pivot. To the best of our knowledge, there is no information in the literature concerning acute toxicity in humans after ingestion of herbicides containing this compound. Method: Six cases of acute poisoning with Arsenal occurred during the period 1993–1997 in a single hospital. Emergency room records and medical charts were reviewed. Results: Of 6 cases, 5 were suicide attempts and 1 was an act of violence inflicted on a child. Three of the 6 patients (50%) presented with severe symptoms, including impairment of consciousness and respiratory distress requiring intubation. Other presentations included metabolic acidosis (2), hypotension (2), leukocytosis (3), fever (2), mild elevation of hepatic transaminase and creatinine (2), unconjugated hyperbilirubinemia (2), oral ulceration (2), pharyngolaryngitis (2), and chemical burns of the cornea (1). All cases had copious vomiting after ingestion of Arsenal. No mortality occurred. Conclusion: According to our observations, it appeared the toxic syndrome that results from a large quantity (> 100 mL) of Arsenal herbicide ingestion consists of hypotension, pulmonary dysfunction, oral mucosal and gastrointestinal irritation, and transient liver and renal dysfunction. However, the existence of a dose-response relationship, with increasing amounts of ingestion resulting in more severe symptoms, needs further observation and studies that include a larger series.