Digoxin
Digoxin is a cardiac glycoside that is used to treat atrial fibrillation and heart failure. In the 1920s, scientists first recognized that some people taking digoxin excreted the inactive metabolite dihydrodigoxin, which is formed by the nonphysiologic reduction of the lactone ring.[8] More recently, studies have identified a certain strain of the gut bacterium Eggerthella lenta as the only possible source of this metabolic process in vivo.[8,14] An estimated 10% of digoxin patients are impacted by this phenomenon, wherein a large proportion of an orally administered digoxin dose is inactivated by the individual's gut flora. In a study conducted by Lindenbaum and colleagues, antibiotic therapy inhibited this deactivation process, resulting in a nearly twofold increase in serum digoxin concentrations.[15]
In addition to determining the specific strain of E lenta responsible for this metabolic process, Haiser and colleagues found that the dietary amino acid arginine decreased digoxin inactivation.[8] Arginine is essential for the growth of E lenta, and in mouse models arginine supplementation appeared to enhance the organism's growth while simultaneously inhibiting its metabolic deactivation of digoxin.[8] The researchers posited that studies of the effects of the gut microbiome might one day inform precision medicine by guiding dietary or supplement-based interventions targeting modifications to gut flora.[8]
US Pharmacist. 2023;48(2):18-22. © 2023 Jobson Publishing
