Effect of physical exercise on the digoxin concentrations in skeletal muscle and serum in man

Summary. Seven healthy men performed an exercise on a bicycle ergometer during one hour after 2 weeks intake of digoxin and with the last dose taken 24 hours before the exercise. Blood samples and skeletal muscle biopsies (m. quadriceps femoris, vastus lateralis) were taken before and after the exercise for analysis of serum and skeletal muscle digoxin concentrations. A percutaneous needle biopsy technique was used for muscle sampling and digoxin was analysed by radioimmunoassay. One minute after completion of the exercise a significantly higher digoxin concentration was found in the thigh muscle than before exercise, indicating an increased digoxin binding in this muscle. Serum digoxin concentration decreased significantly during exercise. After exercise serum digoxin concentration increased again but was still, 30 min after exercise, significantly lower than before exercise.