Scientists are one step closer to creating opioids that relieve pain in a safer, more effective way.

Researchers from the University of North Carolina and collaborators from around the world determined the structure of the activated kappa opioid receptor. They used that to design some new possible drugs that could treat pain without the harmful consequences of those on the market today like morphine and heroin. Their findings were published Thursday in the journal Cell.

Opioids on the market today latch onto several receptors on the surface of cells. They relieve pain but also trigger side effects like nausea, hallucinations and severe dependency. These drugs have been scrutinized for their safety and efficacy, as well as their role in fueling an epidemic that has ripped through the country.

"Tens of thousands of people die in the U.S. every year because of opioid overdoses," said Bryan Roth, the Michael Hooker distinguished professor of protein therapeutics and translational proteomics in the department of pharmacology at the University of North Carolina at Chapel Hill. "There's clearly a need for safer and more effective ways to treat pain and chronic conditions."

The structure will be available for anyone, including drug companies and researchers, to download. They can use that to aid them in computer-assisted drug discovery, Roth said, a process that uses computers to screen up to 100 million compounds at once "basically overnight" to find which compounds might bind to the receptor.

Researchers can run the process without having the structure, which they currently do, but they're "sort of running blind without it," Roth said. Having it will give scientists using the technology a map to work with when they run their tests.

"If you knew where the treasure was hidden, you could use the map to help you get there," he said. "Basically what the structure provides is a map for how you might go about creating safer and more effective medications."

Roth anticipates researchers will start downloading the structure immediately. However, drug development and approval is a lengthy process, so it could be years before new pain treatments resulting from the research are available.