Kristen Philman had already been using heroin and prescription painkillers for several years when, one day in 2014, a relative offered her some methamphetamine, a chemical cousin to the stimulant amphetamine.
"I didn't have any heroin at the time," says Philman, a resident of Littleton, Colo. "I thought, 'Oh this might make me feel better.' "
It did, she says. Soon, she was using both heroin and methamphetamine on a regular basis.