Digoxin concentrations in serum and saliva: relationship to ECG changes and dosage in healthy volunteers.

After 1 week of baseline observations increasing oral doses of digoxin were administered to four healthy volunteers over a 6-7 week period. A dose-response relationship exists with regards to PTQ-changes (a quantitative measure of ECG-changes). PTQ-changes were related linearly to both serum and salivary digoxin levels. PTQ-changes appear to be useful as a non-invasive measure for studying various aspects of digoxin pharmacodynamics. Serial salivary digoxin levels might be a better index of the effect of cardiac glycosides than individual or serial serum levels.