54.

Srbova J, Telsinger J (Clinic Occup. Dis., Prague). Absorption of calcium disodium salt of ethylenediaminetetraacetic acid after oral administration in the treatment of lead poisoning. Archiv fur Gewerbepatholgie und Gewerbehygiene 15. 1957; 6:572-580. (1858) [A new complexometric titration method for the determination of EDTA, using methylthymol blue and xylenol orange as indictors, is described. After oral administration of CaNa2EDTA, Ca and possibly Na are split off in the acid gastric juice while EDTA remains unchanged. CaNa2EDTA is readily soluble in the duodenal juice. Probably no Ca is split off due to the alkalinity of the medium.
In an experiment with 12 adult rats, fasted for 24-48 hr, after ligation of their duodenum, 1 cc of a 20% solution of CaEDTA was injected into the duodenum. The rats were killed after 2 hr and the CaEDTA in the intestines was determined. An absorption of 6.5-26%, av 17.6% of CaEDTA was found. In a control experiment when the animal was killed directly after the injection, 100% of the injected CaEDTA was found.
Four healthy persons were given each a total oral dose of 250 mg CaNa2EDTA in tablets over a period of 8-11 hr; 3 other subjects received the same dose in solution together with alkaline mineral water. An average of 2.5% of the dose was excreted in the urine within 24 hr. After 26 hr, in 2 of the subjects the urine was negative, and for this reason the remaining were not investigated further. Five subjects were given each 6 wafers, consisting of 0.5 g CaEDTA, glucose and syrup, in 3 doses spaced 4 hr apart. An average of 2.8% of the administered CaEDTA was excreted in the urine over 24 hr. It is calculated that 53 mg EDTA/min was excreted by the kidneys and that the EDTA level in the blood was 4 mg%.
According to the authors, the mechanism of the CaEDTA effect is based on the acceleration of the spontaneous exchange of Pb among the blood cells and the surrounding medium. The rate of exchange cannot be increased by administration of high EDTA doses which, furthermore, would cause diarrhea. Another limitation of the EDTA-therapy is based on the fact that EDTA combines in the intestines with metals other than Pb, such as Fe and Cu which may lead to a deficiency of these essential elements. They advise that EDTA be used only for short-term therapy of mild Pb poisonings.

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