A few commonly grown plants are highly poisonous, and many plants are moderately poisonous (see table Moderately Poisonous Plants). Few plant poisonings have specific antidotes. Most plant ingestions, including the plants listed in the aforementioned table, result in minimal symptoms unless the leaves and other components are concentrated into a paste or brewed into a tea.
Highly toxic and potentially fatal plants include the following:
Castor beans and jequirity beans
Oleander and foxglove
Hemlock
(See also General Principles of Poisoning.)
Castor beans and jequirity beans
Castor beans contain ricin, an extremely concentrated cellular poison. Jequirity beans contain abrin, a related and even more potent toxin. In both, the beans have a relatively impervious shell; thus, the bean must be chewed to release the toxin. However, the seed coating of the jequirity bean is often not intact, and simple bacterial digestion can release the abrin toxin.
Symptoms of either poisoning may include delayed gastroenteritis, sometimes severe and hemorrhagic, followed by delirium, seizures, coma, and death. Whole-bowel irrigation should be considered because it aims to remove all beans ingested.
Oleander and foxglove
These plants and lily of the valley (which is similar but less toxic) contain digitalis glycosides. Foxglove was the original source of the drug digitalis. Toxicity includes gastroenteritis, confusion, hyperkalemia, and arrhythmias. The serum digoxin level can confirm ingestion but is not useful as quantitative information.
Potassium levels are closely monitored. Hyperkalemia may respond only to hemodialysis. Calcium is not recommended for arrhythmias. Digoxin-specific fractionated antibody (Fab) fragments have been used to treat ventricular arrhythmias.
Hemlock
Hemlock poisoning (poison hemlock and water hemlock) can cause symptoms within 15 minutes.
Poison hemlock has effects on the nicotinic cholinergic receptor, beginning with dry mouth and progressing to tachycardia, tremors, diaphoresis, mydriasis, seizures, and muscle paresis. Rhabdomyolysis and bradycardia may occur.
Water hemlock seems to enhance gamma-aminobutyric acid (GABA) activity. Symptoms may include gastroenteritis, delirium, refractory seizures, and coma.