Impact of a therapeutic drug monitoring program for digoxin.

Although numerous utilization reviews of serum digoxin assays have demonstrated the positive impact of therapeutic drug monitoring, to our knowledge, the question of whether the withdrawal of such a program would reverse the effect has not been addressed. The current study employed a prospective, randomized, crossover design to evaluate this question and document the cost savings. There were 196 serum digoxin assays performed in the 207 patients. It was found that a continuous therapeutic drug-monitoring program was warranted since, after its withdrawal, there was a deterioration in audit criteria performance. Reimplementation of the therapeutic drug-monitoring program resulted in a significant decrease in the average number of assays requested per patient (from 1.41 to 0.73) and an improvement in audit criteria performance.