Electrochemical effects of metals on IUDs
Zipper, J.; Wheeler, R.G.; Angelo, S.; Adrian, H.
International Journal of Fertility 22(3): 155-161
1977
ISSN/ISBN: 0020-725X PMID: 24009 Document Number: 118845
A series of animal and human studies to measure the intrauterine electrochemical potential, using both polarizable and nonpolarizable electrodes and the effect of this electrochemical activity on IUDs containing copper and zinc are described. Intrauterine voltages in rats measured with Ag-AgC1-(Agar-KC1) electrodes varied from 0 to +20; measured with Cu-Cu electrodes varied from -50 to +50; and measured with Ag-Ag electrodes from -4 to +8. In 7 women comparable measurements were +2 to +10 with Ag-AgC1-(Agar KC1) electrodes spaced 2.5 cm apart along the uterine axis. In 9 women voltage measurements taken with Cu wire electrodes spaced 3 cm apart on the vertical stem of Cu-7 IUD showed readings of -20 to +100. It was assumed that over a prolonged period these intrauterine gradients could accelerate corrosion rates if they had the same polarity as the zinc or copper of an IUD and retard corrosion if the gradient is in opposition to the metal cell potential. When a length of zinc wire was wound around the upper portion of the stem of a small CU-7 200 IUD, it took about 1 year from insertion for the zinc to disappear. When the zinc wire was wound around the lower portion of the stem, it disappeared in 1 month. The zinc reduced intrauterine corrosion of the copper and was more effective when in the lower stem position. Preliminary evidence also suggests that placement of the zinc also influences expulsion rates. This may also be due to polarity, but to date, copper ion concentration studies have not been separated from polarity studies.