Medicinal Use of Foxgloves

Medicines from foxgloves are called "Digitalin". The use of Digitalis purpurea extract containing cardiac glycosides for the treatment of heart conditions was first described by William Withering, in 1785, which is considered the beginning of modern therapeutics (Silverman) It is used to increase cardiac contractility (it is a positive inotrope) and as an antiarrhythmic agent to control the heart rate, particularly in the irregular (and often fast) atrial fibrillation. It is therefore often prescribed for patients in atrial fibrillation, especially if they have been diagnosed with heart failure.

A group of pharmacologically active compounds are extracted mostly from the leaves of the second year's growth, and in pure form are referred to by common chemical names such as digitoxin or digoxin, or by brand names such as Crystodigin and Lanoxin, respectively. The two drugs differ in that Digoxin has an additional hydroxyl group at the C-3 position on the B-ring (adjacent to the pentane). Both molecules include a lactone and a triple-repeating sugar called a glycoside.

Digitalis works by inhibiting sodium-potassium ATPase. This results in an increased intracellular concentration of sodium, which in turn increases intracellular calcium by passively decreasing the action of the sodium-calcium exchanger in the sarcolemma. The increased intracellular calcium gives a positive inotropic effect. It also has a vagal effect on the parasympathetic nervous system, and as such is used in reentrant cardiac arrhythmias and to slow the ventricular rate during atrial fibrillation. The dependence on the vagal effect means that digitalis is not effective when a patient has a high sympathetic nervous system drive, which is the case with acutely ill persons, and also during exercise.

Digitalis toxicity (Digitalis intoxication) results from an overdose of digitalis and causes anorexia, nausea, vomiting and diarrhea, as well as sometimes resulting in xanthopsia (jaundiced or yellow vision) and the appearance of blurred outlines (halos). Bradycardia also occurs. Because a frequent side effect of digitalis is reduction of appetite, some individuals have abused the drug as a weight loss aid.

Digitalis is a classic example of a drug derived from a plant formerly used by folklorists and herbalists: herbalists have largely abandoned its use because of its narrow therapeutic index and the difficulty of determining the amount of active drug in herbal preparations. Once the usefulness of digitalis in regulating pulse was understood, it was employed for a variety of purposes, including the treatment of epilepsy and other seizure disorders, now considered inappropriate.