Interpretation of digoxin blood levels by programmable calculator.

The usefulness of a computer algorithm, for a hand-held calculator, in the calculation of steady-state blood levels of digoxin was studied. The calculator was programmed using the Wagner-Northam steady-state equation. The program was tested on data obtained from the charts of 14 patients recieving digoxin. Blood levels of digoxin were determined by radioimmunoassay. In nine patients, the calculated values correlated well with measured values. In five patients, calculated values did not correlate with measured values; half-life was underestimated in two patients, a charting error was made with one patient and digoxin disappearance was suggested to be unusual in two patients. This study suggests that a measure of scientific precision in planning and monitoring of drug therapy regimens is possible using a programmable calculator.