Internal Medicine

Paraquat poisoning

Paraquat (dipyridylium) is a highly toxic herbicide used worldwide.

Paraquat (dipyridylium) is a highly toxic herbicide used worldwide.


  • Classified as a viologen (family of redox-active heterocycles of similar structure)


  • Quick-acting and non-selective, killing green plant tissue on contact
  • Toxic to human beings and animals due to its redox activity, which produces superoxide anions.
    • Linked to the development of Parkinson’s disease
    • Banned in several countries

Clinical features

(A) ‘Paraquat tongue’ early lesion, within 24 h after ingestion. (B) ‘Paraquat tongue’ late lesion, 2 weeks after ingestion with extensive ulceration | Kasperkiewicz, M., Ellebrecht, C. T., Takahashi, H., Yamagami, J., Zillikens, D., Payne, A. S., & Amagai, M. (2017). Pemphigus. Nature Reviews. Disease Primers, 3, 17026.


Graphical representation of paraquat toxicity inside a pneumocyte and potential sites of antidotal therapy. SOD, superoxide dismutase; CAT, catalase; Gred, glutathione reductase; Gpx, glutathione peroxidase; FR, Fenton reaction; HWR, Haber-Weiss reaction. 1–8: potential sites of action by available treatment options. 1: activated charcoal and Fuller’s earth; 2: dialysis; 3, 4, 6 and 8: salicylates; 5 and 8: N-acetylcysteine; 7 (P-glycoprotein induction): dexamethasone; 4: immunosuppression | Gawarammana, I. B., & Buckley, N. A. (2011). Medical management of paraquat ingestion. British Journal of Clinical Pharmacology, 72(5), 745–757.

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