Kratom has opened a new front in America's drug debate. Manufacturers market the herb—and its highly potent alkaloid, 7-OH—as a breakthrough for pain management. The Drug Enforcement Administration (DEA) is pushing back, arguing that 7-OH acts as a synthetic opioid fueling a new wave of addiction. With the DEA moving to place 7-OH under temporary Schedule I control, the stage is set for a clash between public health advocates and drug legalizati…