If you have been in EMS for a while, you may have been told, at some point, that there is no contraindication to oxygen in the emergency setting. Well, let me burst your bubble. I use this little known fact in many of my classes - as a fun fact of a sort.
"Oxygen is contraindicated in Paraquat poisoning!"
Paraquat is the trade name for one of the most widely used herbicides in the world. Paraquat is a quick-acting and non-selective killer of green plant tissue. It is also toxic to human beings. To touch on an earlier post related to neurology, research has shown that it is linked to development of Parkinson's disease, too.
This abstract from the National Center for Biotechnology Information (NCBI) gives a little more specific information on the subject:
High concentrations of oxygen are known to enhance the toxic effects of paraquat in the lung. We have examined the effects of paraquat (2.5 mg/kg or 20 mg/kg subcutaneously) and diquat (10 mg/kg or 20 mg/kg subcutaneously) on mortality and lung pathology in rats exposed to air or to an atmosphere of 85% oxygen. Our results show a 10-fold increase in mortality when paraquat is given to rats placed in 85% oxygen rather than air, but only a 2-fold increase in the lethality of diquat. Lung damage typical of early paraquat intoxication is seen following 20 mg/kg paraquat in air or oxygen, with damage to type I and type II alveolar cells. Selective damage to the type II cell is produced by lower levels of paraquat (2.5 mg/kg) and by 20 mg/kg diquat, both in 85% oxygen, other cell types showed little change. Lung damage is minimal following 2.5 mg/kg paraquat or 20 mg/kg diquat in air, or exposure to 85% oxygen alone. It is suggested that the type II cell may be the primary target cell for paraquat and diquat in the lung. (http://www.ncbi.nlm.nih.gov/pubmed/6933951)
How about that!
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