Clinically Relevant Digitalis Glycosides
Multiple cardiac glycosides exist and can also be classified as cardiotonic steroids, including digitalis leaf, digitoxin, digoxin, and ouabain (Table 1). Cardiac glycosides, such as peruvoside, have even shown promise in the management of cancer, especially ovarian cancer and leukemia. The cardiac glycosides all have a specific affinity to sodium–potassium adenosine triphosphatase ( Na+/K+-ATPase). These cardiac glycosides, after binding, are highly specific inhibitors of cellular membrane Na+/K+-ATPase, which makes up the so-called cellular sodium pump and which couples membrane ion translocation to high-energy ATP hydrolysis. Cardiac glycosides display functional variability, with different behaviors and therapeutic doses. Digitalis leaf (prepared digitalis) is a raw mix of glycosides obtained from powdered foxglove leaves that requires biological standardization, but activity may still vary from one preparation of tablets to the next. Digoxin, which is the most widely used digitalis derivative, comes from Digitalis lanata (the white foxglove), as does lanatoside-C, which is the glycoside precursor of digoxin. Digitoxin is a pure glycoside obtained from D. purpurea; digitoxin has a slower onset of action than digoxin or lanatoside-C and its much longer half-life means accumulation in the body is greater. Ouabain (strophanthin-G), which is also a pure glycoside, is usually obtained from Strophanthus gratus but can be derived from other vegetable sources. Some clinicians consider ouabain uniquely valuable because of its rapid onset of action when such an effect has been considered advantageous.
Am J Cardiovasc Drugs. 2018;18(6):427-440. © 2018 Adis Springer International Publishing AG