Monensin Toxicity

Toxicology was one of my favorite classes in veterinary school.  I know it sounds crazy, because toxicities are awful and it is really sad when your patients ingest substances that they shouldn’t.  So many of the cases are incredibly tragic like the lily ingestion that waited 3 days to come in.  While others, like the dog who ate 3 pans of brownies, end happily with an evening of chocolate scented vomit.

I think we had a really great professor who made toxicology very engaging and practical.  I also really loved walking around my neighborhood pointing out toxic plants.  Toxic plants are EVERYWHERE!!!  I just noticed that I have pigweed in my back yard.  Sorry dogs, that explains the purple spots on your fur, time to take care of that.

Monensin toxicity is one you should know for your NAVLE prep as this is a very common toxicity of horses with a typical history of someone accidentally giving a horse some cow feed.  

Monensin is a commonly used coccidiostat in feedstuff of cattle. This ionophore is highly toxic to horses and will result in cardiomyopathy and myocardial necrosis. The clinical signs begin 12-24 hours after consumption of an acutely toxic dose but may be delayed for days or weeks in the case of chronic low level intoxication.

Clinical signs include progressive respiratory distress, heart murmur, weakness, and hypovolemic shock. Acutely, mild colic and diarrhea can occur as well but is less of a concern than the cardiovascular effects. Unfortunately, there is no quick and easy antidote, and treatment usually consists of trying to empty the intestinal tract by using mineral oil, activated charcoal, and fluid therapy.

Sadly, there was a recent outbreak of Monensin toxicity in contaminated feed in California and Arizona.  Click here for more information about the recall.  

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