| Abstract: | Summary. Thirteen patients admitted to hospital because of known or suspected cardiac disease who had been treated with digoxin within, at least, the previous month were investigated. Blood samples for serum digoxin analysis by radioimmunoassay were taken before and after 40 min rest in supine in the ward and later in the outpatient clinic, all samples taken about 24 h after the last dose of digoxin. The serum digoxin concentration measured before rest in the outpatient clinic was significantly lower than those measured in the ward before and after rest. This is possibly related to physical activity prior to blood sampling since after 40 min rest in the outpatient clinic the serum digoxin concentration had increased and the concentration after rest was not significantly different from the concentrations measured in the ward. In analogy with a previous finding of a decrease in serum digoxin concentration during exercise in healthy subjects ingesting digoxin, the present results suggest that everyday physical activity affects the serum digoxin concentration. This must be taken into account when interpreting the results of serum digoxin measurements. |
