Abstract
The method commonly employed for determination of vitamin C in the body fluids makes use of Tillmans' 1 indicator, 2,6 dichlorophenol indophenol. This is not specific for the vitamin but under controlled conditions is practically so. Substances normally present in urine, namely cysteine, glutathione, and ergothioneine, 2 may reduce the dye, but Abbasy and coworkers 3 have reported that the non-specific titer did not rise above 3 to 6 mg. per day for the average person. In many specimens from our patients, where vitamin C was excluded from the diet, total excretion of “vitamin C” varied from less than one to 4 mg. in 24-hour specimens. Such interference, therefore, seems to be unimportant in the majority of cases. We have found, however, that Pyridium, (phenylazo-diamino-pyridine hydrochloride), a commonly used medication for disorders of the urinary tract, may constitute a serious source of error in blood 4 and urine 5 determinations of the vitamin.
In one instance, a patient's excretion following a test dose, 1000 mg. intravenously, 6 of crystalline ascorbic acid,∗ decreased daily from 94 mg., to 32 mg., to 4 m'g., and the next day the result obtained was 137 mg. On that day, however, 6 Pyridium tablets had been given in treatment of cystitis unr'elated to the hypovitaminosis. The urine was (diluted and titrated, and a distinct endpoint duplicated. This was the first apparent rise in excretion without increased intake in this subject. After the cystitis had disappeared a test dose of 1000 mg. orally and 6 Pyridium tablets were given for experimental purposes. The result obtained at a dilution of 1:40 was 385 mg., but after the specimen had stood in the refrigerator for 48 hours, the quantity present appeared to be 430 mg.
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