Inactivation of digoxin by Eubacterium lentum, an anaerobe of the human gut flora.

Digoxin is converted to cardioinactive reduced metabolites (DRP) in vivo and in vitro by the human gut flora. Digoxin inactivation is mediated by Eubacterium lentum, a normal inhabitant of the gastrointestinal flora. E. lentum appears to be the sole organism performing this reaction. Fecal bacteria that convert digoxin to DRP in vitro have been found to be present in some subjects who fail to make DRP in vivo. DRP-forming E. lentum have been isolated from the stools of two such subjects. When increasing amounts of arginine are supplied as a growth substrate to E. lentum, bacterial growth and DRP production vary inversely. Further study will be required to identify the factors which determine why digoxin is inactivated in vivo by the gut flora of certain patients and not by others.