NIGHTTIME DOSING ASSURES POSTDISTRIBUTION SAMPLING FOR THERAPEUTIC DRUG-MONITORING OF DIGOXIN

To study the appropriateness of phlebotomy for digoxin therapeutic dru g monitoring (TDM) in outpatients, we conducted a retrospective chart review, a computer search of all previous TDM testing, and a questionn aire 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 d ose, No patient who took digoxin after 1700 had inappropriate tests. P hlebotomy for serum digoxin determinations before distribution of digo xin is complete is a common problem in outpatients, leading to clinica lly uninterpretable test results, Post-distribution sampling can be as sured by nighttime dosing, and this recommendation has been implemente d at our hospital.