Burst release of ions from copper-based intrauterine devices (IUD) occurs during the first day after the insertion in uterus and may induce side effects in the users. In the present work, we investigate the mechanism of the inhibitory action of ex-situ pretreatment of copper samples with purine (10(-2)-10(-4) M PU) in simulated uterine fluids (SUF) with and without urea (UR). Quartz crystal microbalance measurements showed that the PU inhibition effect depends on the concentration and adsorption time increasing in presence of chloride. In particular, PU pretreatment (10(-2) M-10(-3) M) leads to an inhibition of copper ions release over 24 h immersion time in SUF, without and with UR. UR may act for a few hours as a weak corrosion inhibitor leading to temporary control of corrosion, but the protection decreases quickly due to formation of soluble Cu-UR complexes, being the total amount of released copper higher when UR is present. (C) 2015 Elsevier Ltd. All rights reserved.