Irritation effects of residual products derived from p(HEMA) gels. II. Compounds extracted from hydrogels.

Samples of poly(2-hydroxyethyl methacrylate) p(HEMA) hydrogels were prepared using three different polymerization initiators. The gels were washed in water under standard conditions. The extracts were then examined for intradermal irritation in rats using a radioactive indicator (113mIn). The irritation effects were dependent on the concentrations of the irritating substances and also on the gel type. Solid discs made of the gels, washed to varying degrees of purity, were also implanted into rats. Tissue irritation, as well as some other biological responses, were followed in situ using the radioindicator and common histological techniques. The irritation effects were very mild (even with the unextracted gel material). A possible explanation for the events taking place at the site of implantation is presented.