Rhododendron spp. (including Azalea spp.)
Why is it risky?
Azaleas and rhododendrons contain grayanotoxins, diterpenes that lock open sodium channels in cell membranes, causing persistent depolarization of nerve and cardiac muscle cells. This produces cardiovascular and neurological dysfunction. Ingestion of as little as 0.2% of body weight in leaves can cause clinical signs. Azaleas are among the most widespread garden shrubs in temperate regions.
Affected Systems
Digestive · Nervous · Cardiovascular
Symptoms
Hypersalivation, vomiting, diarrhea, ataxia, weakness, bradycardia, hypotension, abnormal cardiac rhythm, tremors, progressive to respiratory failure and collapse.
What To Do
Emergency vet. Cardiac monitoring is essential, grayanotoxin causes potentially fatal rhythm disturbances. Atropine for bradycardia, IV fluids, supportive care.
Notes
All Rhododendron species should be assumed to contain grayanotoxins. This includes potted miniature azaleas frequently sold as gift plants at Easter and Mother's Day. Honey produced from rhododendron flowers can contain grayanotoxins ("mad honey"), though primarily a human concern, it illustrates the potency of these compounds.
Sources
→ ASPCA Animal Poison Control Center — aspca.org/pet-care/aspca-poison-control/toxic-and-non-toxic-plants/azalea
→ Pet Poison Helpline — https://www.petpoisonhelpline.com/poison/rhododendrons/
→ Merck Veterinary Manual — merckvetmanual.com