The potent class of prescription opioids is known as transmucosal immediate-release fentanyls (TIRFs). These painkillers, which are fast-acting and powerful, are intended to help breakthrough pain in cancer patients, whose normal opioid pain relievers aren’t managing all the pain. “This is not a usual drug,” says Caleb Alexander, a Johns Hopkins professor of medicine and the corresponding author of the new study. It’s a last-resort drug. For that reason, he says, in 2011, the FDA instituted a very restrictive program, known as the Risk Evaluation and Mitigation Strategy for TIRFs, or TIRF REMS.