Reversibility of the contraceptive action of copper and zinc in the rat and rabbit

Zinc as a non-hormonal contraceptive: an alternative to the copper intrauterine device (IUD)

Long-acting and reversible contraceptives (LARC) are the most widely used form of female contraception worldwide, however they have significant side-effects that often result in early removal. Most LARCs are hormonal, but the use of exogenous hormones is not suitable for all women and causes side-effects in many others. The copper IUD (CuIUD) is the only non-hormonal LARC, but a large proportion of users suffer severe side effects. This study proposes the use of zinc as a suitable alternative to the CuIUD. A rat intrauterine device (IUD) model was established to test the efficacy of a zinc IUD (ZnIUD) against a CuIUD. The IUD was surgically implanted into one uterine horn while the other remained untreated. Both the ZnIUD and CuIUD resulted in zero implantation sites which was significantly fewer compared to non-treated horns. Histological assessment revealed damage and inflammation in the endometrium of CuIUD treated horns, but only minor epithelial changes in ZnIUD treated horns. This suggests ZnIUDs may not share the side-effect profile of the CuIUD. To test the long-term efficacy of the ZnIUD, rats had a ZnIUD surgically implanted into both horns and cohoused with males for 3 months. These rats mated regularly but did not get pregnant, confirming long-term effectiveness. Reversibility of the ZnIUD was also established, as removal of the ZnIUD after 3 months resulted in no significant difference in the number of implantation sites between treated and untreated horns. This study demonstrated the contraceptive efficacy of zinc and its potential as a LARC.

Zn(2+) release behavior and surface characteristics of Zn/LDPE nanocomposites and ZnO/LDPE nanocomposites in simulated uterine solution

To decrease the side effects of the existing copper-bearing intrauterine devices, the zinc/low-density polyethylene (Zn/LDPE) nanocomposite and zinc-oxide/low-density polyethylene (ZnO/LDPE) nanocomposite have been developed in our research for intrauterine devices (IUDs). In this study, the influences of preparation methods of nanocomposites and particle sizes of zinc and zinc oxide on Zn(2+) release from composites incubated in simulated uterine solution were investigated. All release profiles are biphasic: an initial rapid release phase is followed by a near zero-order release period. Zn(2+) release rates of nanocomposites prepared by compressing moulding are higher than those of the nanocomposites prepared by hot-melt extrusing. Compared with Zn(2+) release from the microcomposites, the release profiles of the nanocomposites exhibit a sharp decrease in Zn(2+) release rate in the first 18 days, an early onset of the zero-order release period and a high release rate of Zn(2+) at the later stage. The microstructure of the Zn/LDPE sample and the ZnO/LDPE sample after being incubated for 200 days was characterized by SEM, XRD and EDX techniques. The results show that the dissolution depth of ZnO/LDPE nanocomposite is about 60 mum. Lots of pores were formed on the surface of the Zn/LDPE sample and ZnO/LDPE sample, indicating that these pores can provide channels for the dissolution of nanoparticles in the matrix. The undesirable deposits that are composed of ZnO are only detected on the surface of Zn/LDPE nanocomposite, which may increase the risk of side effects associated with IUDs. It can be expected that ZnO/LDPE nanocomposite is more suitable for IUDs than Zn/LDPE nanocomposite.

The effect of intrauterine devices containing zinc and copper on their levels in serum

Serum levels of copper and zinc were determined in 11 health women in whom Latex Leaf intrauterine devices (IUDs) containing copper and zinc had been inserted. Patients with low levels of serum copper or zinc before insertion usually had increased levels of either of these metals while using the device, but they did not exceed the upper limits of normal values. When the group was considered as a whole, the serum levels of zinc showed a slight tendency to increase with duration of IUD use, whereas there was no statistical difference between the serum levels of copper before and after insertion of the IUD.