Foxglove (Digitalis purpurea 'Giant Shirley') flowers. The foxglove plant contains the poisonous chemical digitalin. Consuming the plant causes vomiting, hallucinations and even death from disorganised pumping of the heart. In modern medicine, drugs based on the poison are used to treat heart failure, arrhythmia (irregular heartbeat) and fibrillation (rapid, disorganised heartbeat). The most commonly-used drugs derived from the foxglove are digoxin and digitoxin. The foxglove is a common plant throughout much of Europe and North America.