To combat the epidemic, the president said the government would produce “really tough, really big, really great advertising” aimed at persuading Americans not to start using opioids in the first place, seeming to hark back to the “Just Say No” antidrug campaign led by Nancy Reagan in the 1980s.“This was an idea that I had, where if we can teach young people not to take drugs,” Mr. Trump said, “it’s really, really easy not to take them.” He shared the story of his brother Fred, who he said had struggled with alcohol addiction throughout his life and implored Mr. Trump never to take a drink — advice the president said he had heeded.