Chlormerodrin is a mercurial diuretic commercially traded from 1952 until 1974 that was once used to treat patients with heart failure, but is no longer in widespread use. The radiolabelled form (<sup>197</sup>Hg & <sup>203</sup>Hg) had also been used for medical imaging of the kidney and brain and the <sup>197</sup>Hg form was even considered a contender for <sup>99m</sup>Tc by some physicians, but was ultimately discontinued by the FDA in 1989.