ACHE and respiratory depression: However, exposure to parathion (and its subsequent metabolite paraoxon) can result in headaches, nausea, respiratory depression, seizures and significant and irreversible effects arising from the inhibition of acetylcholinesterase (Edwards, Yedjou, & Tchounwou, 2013; Reigart, 2013; Satar, Tap, & Ay, 2015).