Digitalis

Digitalis is a drug that has been used for centuries to treat heart disease. The active ingredient in the drug is glycoside, a chemical compound that contains a sugar molecule linked to another molecule. The glycoside compound can be broken down into a sugar and nonsugar compound. Though current digitalis drugs are synthetic, that is, man-made, early forms of the drug were derived from a plant.

Digitalis is a derivative of the plant Digitalis purpurea, or purple foxglove. The plant's name, Digitalis (from the Latin digit, finger) describes the finger-shaped purple flowers it bears. The effects of the plant extract on the heart were first observed in the late eighteenth century by William Withering, who experimented with the extract in fowls and humans. Withering reported his results in a treatise entitled, "The Foxglove and an Account of its Medical Properties, with Practical Remarks on Dropsy." His explanations of the effects of foxglove on the heart have not stood up to the test of time, but his prediction that it could be "converted to salutary ends" certainly has. Indeed, digitalis remains the oldest drug in use for the treatment of heart disease, as well as the most widespread, in use today.

The digitalis drugs come in many forms, differing in their chemical structure. As a group they are classified as cardiac inotropes. Cardiac, of course, refers to the heart. An inotrope is a substance that has a direct effect on muscle contraction. Positive inotropism is an increase in the speed and strength of muscle contraction, while negative inotropism is the opposite. Digitalis has a positive inotropic effect on the heart muscle.