ABSTRACT
Digitalis purpurea, purple foxglove, and Digitalis lanata, woolly or Grecian foxglove, are now members of the Plantaginaceae family. The family is famous for being the source of a large number of different cardiac glycosides with actions on the heart, in particular two medicines, digitoxin from D. purpurea and both digitoxin and digoxin from D. lanata. Digoxin (and digitoxin) exert their effects by inhibiting the ATPase activity of a complex of transmembrane proteins that form the sodium/potassium ATPase pump which normally pumps sodium out of cardiac muscle cells. Digoxin is still used in modern times for the treatment of heart failure and atrial fibrillation. However, digitoxin and digoxin have steep doseresponse curves; thus, minute increases in the dosage of these drugs can make the difference between an ineffective dose, a therapeutic dose and a fatal one.
