HMM: This engineered painkiller works like an opioid but isn’t addictive in animal tests. “Using pain-relieving peptides released by the brain as models, Fernandez and colleagues developed a library of ‘peptidomimetics.’ These agents were small enough to get into the brain, and they worked on different opioid receptors in different ways. When they tested one such compound in mice, they found that it not only relieved pain, it also induced less buildup of tolerance and less physical dependence than morphine. In other words, it was less addictive.”