Digoxin therapeutic drug monitoring practices. A College of American Pathologists Q-Probes study of 666 institutions and 18,679 toxic levels.

Abstract

We investigated digoxin therapeutic drug monitoring practices in 666 institutions participating in Q-Probes, a quality improvement program of the College of American Pathologists. Participants used 13 different lower and 16 different upper limits for their therapeutic range. More than 280,000 digoxin levels were studied, and 6.7% (n = 8679) of results were in the toxic range (> 2.6 nmol/L). For the 77% of patients with toxic levels, the last digoxin dose was given orally; for 23% of patients, it was given intravenously; and for less than 1%, it was given intramuscularly. Between 22% and 31% of specimens in the toxic range were obtained before steady state had occurred, depending on the criteria used. Small institutions (less than 150 beds), outpatients, stat specimens, and laboratory policies not requiring the time of the last dose before measurement were associated with higher percentages of specimens drawn before the recommended time had elapsed. We describe digoxin monitoring practice patterns and provide suggestions for improvement.