This article is from the Pet Owner's Guide to Common Small Animal Poisons, by Julie Dahlke, DVM, a graduate of the University of Minnesota, College of Veterinary Medicine.
Scientific name -- Many, including: Rhododendron, Nerium oleander,
Common names -- Rhododendrons, milkweeds, lily-of-the-valley, laurel,
oleander, azalea, foxglove, etc.
This group of common plants all contain cardiac glycosides. Cardiac
glycoside drugs derived from one of these plants, digitalis
(foxglove), have been used for many years in the treatment of heart
disease in people and animals. Due to their actions on the heart,
however, ingestion of plants containing glycosides can be fatal. Signs
may include vomiting, diarrhea, collapse, or death from heart
failure. Fortunately, the plant has a bitter and very unpleasant
taste! Nonetheless, the American Association of Poison Control Centers
(AAPCC) report covering 425 fatal animal poisonings in 1990 includes 4
resulting from cardiac glycoside-containing plants.