Drug Interference with the Trihydroxyindole Method for Free Catecholamines in Urine

摘要

Thirty-five of 108 drugs tested may interfere with the trihydroxyindole fluorometric method for urinary free catecholamines. Screening for interference was accomplished by testing the total daily dose of a drug or portion thereof for possible fluorescence. Further information was obtained by adding a similar dose for each of 16 interfering drugs to 150 ml of fresh, pooled urine containing 67 ng/ml each of norepinephrine and epinephrine. Additional studies of seven interfering drugs were conducted using healthy males and assaying catecholamines from 4-h urine specimens. Four possible modes of interference were observed: (1) substances which reacted to form fluorescent products, such as thiamine hydrochloride and ascorbic acid; (2) substances with native fluorescence, such as riboflavin; (3) substances which are intensely colored in solution and interfered with fluorescent excitation or emission spectra, such as phenazopyridine hydrochloride; and (4) substances which inhibited catecholamine extraction onto alumina, such as methenamine mandelate. This work has expanded upon data previously available in identifying drugs which may spuriously alter urinary free catecholamine excretion measured by the trihydroxyindole procedure. (Author)