Regarding Paraquat Poisoning..

A 54-yr -old woman gardener with long-standing depression presents to A&E following a deliberate suicide attempt by ingestion of the pesticide paraquat.

Which of the following statements is true following exposure to paraquat?
A. The principal site of toxicity is the GI tract
B. Pulmonary fibrosis is an early cause of death
C. Supplemental oxygen may increase paraquat toxicity
D. Toxicity is directly due to the paraquat
E. Survival is common after the ingestion of 5 g of paraquat


Answer:
C--Supplemental oxygen may increase paraquat toxicity

Discussion: Paraquat is a very toxic compound and as little as 2 g can be potentially fatal (10 ml of a
concentrated 20% solution). Initial signs of toxicity are due to its corrosive effects on the GI tract and oropharynx. Paraquat is rapidly absorbed and is sequestered in the lungs, where it reacts with oxygen to form hydrogen peroxide and superoxide anions. These are responsible for cell death, which leads to an acute alveolitis. Death tends to occur within hours to days in patients who have ingested more than 6 g of paraquat, and in days in those who have ingested 3–6 g. Ingestion of 1.5–3 g follows a much more protracted course and delayed pulmonary fibrosis can lead to death up to 6 weeks after ingestion.

Management involves providing supportive care and the use of activated charcoal to reduce absorption. Excessive oxygen supplementation can actually increase pulmonary toxicity, by increasing the rate of hydrogen peroxide and superoxide anion production.