Including cardiac glycosides. Discovered by Dr Withering (1785) who was the first physician to prescribe Foxglove for heart disorders. Glycosides are water-soluble constituents of a plant which when heated with dilute acid, or in the presence of an enzyme, are resolved into two or more substances, one of which is sugar. Thus, the root of Horseradish contains the glycoside sinigrin which is decomposed in the presence of water by the ferment myrosin. Cardiac glycosides occur in Lily of the Valley (used as an alternative to Foxglove), Bitter root and Strophantus. An important group of glycosides (flavonoid glycosides) are found in the labiatae family – a family well-represented among medicinal plants.
Drugs whose main actions are to increase the force of myocardial contraction and reduce the conductivity of the nerve ?bres in the atrioventricular node of the heart. They are useful in treating supraventricular tachycardias (rapid heart rhythm) and some forms of heart failure. Glycosides are a traditional group of cardiac drugs, originally derived from the leaves of foxglove plants and used as digitalis. The active principle has long been synthesised and used as DIGOXIN. They are potentaially toxic and their use, especially during initial treatment, should be monitored. Side-effects include ANOREXIA, nausea, vomiting, diarrhoea and abdominal pain; drowsiness, confusion and DEPRESSION may occur. An abnormally slow heart rate may develop. The glycosides should be used with special care in the elderly who are sometimes particularly susceptible to their toxic effects.... cardiac glycosides
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