Foxglove leaves are claimed to be used externally by Welsh physicians and its poisonous nature was well known. It has been recorded to be used by a ‘witch’ healer for the treatment of dropsy. Though introduced into the London pharmacoepia in 1650, it was with William Withering’s published clinical findings in 1776 that it came into frequent use. It began to be investigated chemically since 1820. Digitalis was thus used medicinally as leaf, standardized leaf powder and as isolated active constituents. On account of the pronounced cardiac effects of digitalis, the variability in the glycoside content and also differences in the range of structures present due to enzymatic hydrolysis, the crude leaf is assayed biologically. Based on this, the leaf powder was standardized for active glycosides and diluted as required with powdered low-potency digitalis, or with powdered lucerne or grass.

While D. purpurea was earlier used as a crude drug, D. lanata was never used so. Both are now replaced by pure isolated glycosides. The cardioactive glycosides increase the force of contractions in the heart, thus increasing the cardiac output and allowing more rest between contractions. The improved blood circulation tends to improve kidney function, leading to diuresis and loss of oedema fluid often associated with heart disease. However, the diuretic effect historically important in the treatment of dropsy is now more safely controlled by other diuretic drugs. Digitoxin, digoxin, lanatoside C and desacetyl lanatoside C (deslanide) are the isolated constituents employed in therapy. Acting similar to digitalis leaf, digoxin however has a rapid action. It is more rapidly absorbed from the gastrointestinal tract and is more quickly eliminated than digitoxin and is therefore the more widely used of the cardioactive glycosides. It is also more hydrophilic than digitoxin and binds less strongly to plasma proteins and is mainly eliminated by the kidneys, whereas digitoxin is metabolized more slowly by the liver. Over the past decades, digoxin has become the most widely used drug in the treatment of congestive heart failure. Proprietary preparations of lanatoside A and C are available in various countries but digoxin is more widely used. It is used for rapid digitalization in the treatment of atrial fibrillation and congestive heart failure. Lanatoside C is less absorbed than digitoxin, but it is less cumulative and for rapid digitalization, digoxin is preferred.