Digitalis is a chemical derived from the foxglove (Digitalis purpurea) which acts on the muscle and conducting systems of the heart. The English physician William Withering in 1783 first described its effectiveness in treating heart failure (then known as dropsy); it increases the force of cardiac contraction. Digitalis is also valuable in the treatment of some arrhythmias (abnormal heartbeat); however, overdosage may itself cause abnormal rhythms, nausea, or vomiting.

 

Digitalis is the basis for a group of pharmaceuticals used to treat various heart conditions, the most commonly used of which are digoxin and digitoxin.

 

Digitalis is typical of biologically active complex compounds found in nature. The three-ring phenanthrene residue in the lower half of the molecule is common also to such compounds as steroids and hormones, cholesterol, and the human male and female sex hormones.