Mechanisms of toxicity, clinical features, and management of diquat poisoning: A review

Uses: Diquat (1,1'-ethylene-2,2'-bipyridilium) is a nonselective bipyridyl herbicide, related structurally to paraquat, which is used both as a contac t herbicide and a preharvest desiccant. In comparison to paraquat, diquat i s used much less widely in agriculture. Mechanisms of Toxicity: Diquat is a potent redox cycler and is readily converted to a free radical which, in r eaction with molecular oxygen, generates superoxide anions and subsequently other redox products. These products can induce lipid peroxidation in cell membranes, and potentially cause cell death. Features: Over the period 196 8-1999, only 30 cases of diquat poisoning were reported in detail in the li terature, of which 13 (43%) were fatal. Local and systemic effects have bee n reported following diquat exposure with systemic features being invariabl y associated with ingestion. In severe and usually fatal cases, gastrointes tinal mucosal ulceration, paralytic ileus, hypovolemic shock, acute renal f ailure, and coma have been reported. Management: After rapid confirmation o f the diagnosis using a qualitative urine test, gut decontamination may be considered in patients who present within 1 hour of a life-threatening inge stion (>6 g). Supportive measures including fluid and electrolyte replaceme nt should then be employed. Although hemofiltration and hemodialysis are of proven value if renal failure supervenes, there is no clinical evidence th at hemodialysis or hemoperfusion removes toxicologically significant amount s of diquat, thereby reducing the risk of organ failure and preventing a fa tal outcome in severe cases.