The Los Angeles Times reports scientists are "tantalizingly close" to the perfect painkilling drug. Researchers announced the discovery of PZM21 in a study published Wednesday in Nature. In testing on mice, the chemical compound relieved nearly as much pain as morphine—87% to 92%—and lasted longer. At the same time, it didn't appear to lead to addiction. Quartz explains this is likely because PZM21 doesn't cause a release of dopamine as does morphine and other opioid painkillers. That's huge because deaths from opioid overdoses have quadrupled since 1999, and the CDC is telling doctors to prescribe fewer of the painkillers. PZM21 also didn't cause constipation in mice, another side effect of opioids.
But PZM21 wasn't without its problems. Like opioid painkillers, it caused dangerously slow breathing in mice. Still, study author Aashish Manglik tells Bloomberg researchers are "cautiously optimistic" about the drug's potential. Human testing—likely a few years away—is when that potential will truly be known, as Manglik says addiction is "really a human disease." PZM21 was the result of researchers using a computer to run 4 trillion simulations on more than 3 million chemical compounds in a search for one that best fits a specific opioid receptor in the brain and spinal cord. (Getting painkillers can be difficult—if you're black.)