[Endogenous digitalis-like substances and cardiac glycosides: facts and hypotheses].

The review presents the data on endogenous digitalis-like substances the effects of which are imitated by administered cardiac glycosides. It is suggested that the individual differences in the responses of patients to cardiac glycosides, a great range of doses of the drugs causing intoxication as well as the absence of a close correlation between the occurrence of therapeutic and toxic effects and blood plasma glycoside concentration are related to the change of the level of endogenous digitalis-like substances in the organism. The further study of the chemical structure of digitalis-like substances and the mechanism of their secretion opens up new possibilities for practical medicine.