Nighttime dosing assures postdistribution sampling for therapeutic drug monitoring of digoxin
D W Bernard1, R L Bowman, F A Grimm
1Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical Center, Hospital of the University of Pennsylvania, Philadelphia 19104, USA.
Abstract:
To study the appropriateness of phlebotomy for digoxin therapeutic drug monitoring (TDM) in outpatients, we conducted a retrospective chart review, a computer search of all previous TDM testing, and a questionnaire of all outpatients (n = 86) who had serum digoxin determinations between April 10 and April 28, 1992 (585 tests). In patients who took digoxin at the same time daily (40 patients, 300 tests), 52% of tests were performed on inappropriate samples drawn within 6 h of the last dose. No patient who took digoxin after 1700 had inappropriate tests. Phlebotomy for serum digoxin determinations before distribution of digoxin is complete is a common problem in outpatients, leading to clinically uninterpretable test results. Postdistribution sampling can be assured by nighttime dosing, and this recommendation has been implemented at our hospital.
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