Nightshade and Ivermectin: A Deadly Mixture

Editor's note: When researching the unknown illness story on this page, the following study on ivermectin's interaction with a noxious weed was discovered. Nightshade and other poisonous plants should be eliminated from pastures.

Texas A&M University (TAMU) researchers published a study in 1998 describing the deadly combination of Silverleaf nightshade (Solanum elaegnifolium) and ivermectin dewormers. They used rabbits as research models in the study, since horses and rabbits have similar digestive tracts. They performed the study after reports of the toxic interaction in horses.

S. elaegnifolium is a perennial native to many areas of the United States. The leaves and fruit are toxic at all stages of maturity.

Murl Baily Jr., DVM, MS, PhD, Dipl. ABVT, a TAMU veterinary toxicologist, said, "Rabbits, when eating S. elaegnifolium and given ivermectin, had higher ivermectin brain levels than those rabbits not ingesting the nightshade. The ivermectin levels in the rabbit brains were similar to those...in horses eating Silverleaf nightshade and receiving a therapeutic dose of ivermectin."

Within 20 hours of ivermectin dosage, horses also ingesting the plant exhibited ataxia (incoordination), drooling, droopy lips and ears, head pressing, depression, muscle tremors, lateral recumbency, and they often died.

The study concluded, "It is possible that S. elaegnifolium may promote absorption of ivermectin into the brain."

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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