Physical exercise and digoxin binding to skeletal muscle: Relation to exercise intensity

Summary

The effect of a 1 h bicycle exercise test on digoxin concentration in skeletal muscle (thigh) and serum was studied in 10 healthy men, who had ingested digoxin 0.5 mg daily for 2 weeks. During maintenance digoxin treatment each subject performed 2 exercise tests, at 70–90 W and 140–180 W both 24 h after the last dose, at a 2–7 day interval. During exercise at the lower work load the mean skeletal muscle digoxin concentration increased by 9% (n.s.) and the mean serum digoxin concentration decreased by 26% (p<0.001). The high work load induced a mean increase in skeletal muscle digoxin of 20% (p<0.05) and a mean decrease in serum digoxin of 40% (p<0.001). The results indicate that the increased uptake of digoxin into exercised skeletal muscle and the decrease in serum digoxin during exercise is related to the intensity of the exercise.