merbromin, antiseptic used to prevent infection in small cuts and abrasions. Commonly marketed as Mercurochrome, merbromin was the first of a series of antiseptics that contained mercury, a chemical element that disinfects by disrupting the metabolism of a microorganism. Merbromin stains surrounding tissue a brilliant red tinged with a yellow-green fluorescence. It is only a weak antiseptic and has been displaced in medicine by the more effective agents of the series, including nitromersol (Metaphen) and thimerosal (Merthiolate), and by antibiotics.