Paraquat

Paraquat is widely available as a selective weedkiller which is inactivated on contact with the soil. A dose of 2-3g is usually fatal (equivalent to 80-120g of granules or 10-15ml of industrial liquid concentrate).

Clinical features

• Very little of the ingested paraquat is absorbed from the gut but a large dose will lead rapidly to shock with widespread tissue necrosis.

• A burning sensation in the mouth and abdomen is more common in poisoning, as is the development of painful mouth ulcers and, after several days, a relentless, proliferative alveolitis causing death by pulmonary fibrosis.

Management

• Treatment should begin on clinical grounds in view of the severity of toxicity and the time taken for laboratory confirmation.

• Urgent gastric emptying is required with instillation of 500ml water containing 150g Fuller's earth and 25g magnesium sulphate afterwards.

• Severe diarrhoea may ensue requiring careful fluid management.

• If paraquat poisoning is confirmed 200-500ml of 30% Fuller's earth is given 2-hrly for 24h via a nasogastric tube.

• A forced diuresis should be started to encourage renal excretion.

• Pulmonary fibrosis is more severe when breathing high oxygen concentrations; if oxygen is required the lowest concentration possible should be given accepting a low PaO2. Liposomal superoxide dismutase and glutathione peroxidase have been used experimentally.

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