Acute poisoning with a herbicide containing imazapyr (Arsenal): A report of six cases

Background: Acute pesticide poisoning is a major cause of morbidity and mor tality 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 he rbicide, recently registered in Taiwan under the tradename "Arsenal" (Imaza pyr 23.1%, Cyanamid Taiwan Corporation, Taipei). Imazapyr is also marketed as Assault, Chopper, Contain, and Pivot. To the best of our knowledge, ther e is no information in the literature concerning acute toxicity in humans a fter ingestion of herbicides containing this compound. Method: Six cases of acute poisoning with Arsenal occurred during the period 1993-1997 in a sin gle hospital. Emergency room records and medical charts were reviewed. Resu lts: Of 6 cases; 5 were suicide attempts and 1 was an act of violence infli cted on a child. Three of the 6 patients (50%) presented with severe sympto ms, including impairment of consciousness and respiratory distress requirin g intubation. Other presentations included metabolic acidosis (2), hypotens ion (2), leukocytosis (3), fever (2), mild elevation of hepatic transaminas e and creatinine (2), unconjugated hyperbilirubinemia (2), oral ulceration (2), pharyngolaryngitis (2), and chemical burns of the cornea (1). All case s had copious vomiting after ingestion of Arsenal. No mortality occurred. C onclusion: According to our observations, it appeared the toxic syndrome th at results from a large quantity (> 100 mL) of Arsenal herbicide ingestion consists of hypotension, pulmonary dysfunction, oral mucosal and gastrointe stinal irritation, and transient liver and renal dysfunction. However, the existence of a dose-response relationship, with increasing amounts of inges tion resulting in more severe symptoms, needs further observation and studi es that include a larger series.