An Audit of Requests for Therapeutic Drug Monitoring of Digoxin

Abstract
The use of serum digoxin measurements [used to detect digoxin toxicity] in a teaching hospital was audited. The reason for test requisition, the timing of blood samples, the recognition of results and the action taken by house staff were assessed using formal criteria. In 200 consecutive requests for serum digoxin measurements, the reason for requesting the test could not be determined in 165 (82.5%). The timing of plasma samples with respect to duration of therapy [control of atrial fibrillation] and time since last dose was usually satisfactory. Only 73 (36.5%) were apparently adequately recognized, and approximately 1 result in 4 was followed by an inappropriate decision. High plasma concentrations were usually dealt with more promptly and more appropriately than low plasma concentrations, possibly because the biochemistry laboratory informed physicians directly of the high results. There is a clear need for physicians to better identify the reasons for measuring plasma concentrations of digoxin and to request serum digoxin measurements only when there is a pertinent problem. Indiscriminate requests for serum digoxin measurements are associated with apparent disregard for the results and a high likelihood of making an inappropriate decision regarding further digoxin prescription.

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