Pain management and addiction are two important and often related challenges in the medical world but some help may be coming from an unlikely source: poison frogs, which are immune to their own toxins.

The research, published in Science, highlighted how a change in three out of 2,500 amino acids allowed a subgroup of poison frogs that use epibatidine to become resistant to its damaging effects. The toxin binds itself to receptors in an animal’s nervous system and this can cause hypertension, seizures, and in some cases, death. But not in these frogs. Surprisingly the same change in amino acids has evolved independently three times in poison frogs.

“Being toxic can be good for your survival — it gives you an edge over predators,” co-first author Rebecca Tarvin, from the University of Texas, Austin, said in a statement. “So why aren’t more animals toxic? Our work is showing that a big constraint is whether organisms can evolve resistance to their own toxins. We found evolution has hit upon this same exact change in three different groups of frogs, and that, to me, is quite beautiful.”

This evolution is not just beautiful but it could have a big impact on pain management. Epibatidine is a powerful non-addictive painkiller and it would be incredibly effective if it weren’t for its dangerous side effects. So understanding how frogs can block this toxin might help design a pain medication that doesn’t cause addiction.

“Every bit of information we can gather on how these receptors are interacting with the drugs gets us a step closer to designing better drugs,” added Cecilia Borghese, another co-first author of the paper and a research associate in the university’s Waggoner Center for Alcohol and Addiction Research.

The change in amino acids have the receptors to be unaffected by epibatidine without this change affecting the receptors’ healthy functioning. The receptor becomes in a way more selective of the compounds it can bind with.

“The most exciting thing is how these amino acids that are not even in direct contact with the drug can modify the function of the receptor in such a precise way,” Borghese continued. “And now the receptor is resistant to epibatidine. That for me was fascinating.”

In humans, the receptor in questions is involved in both pain and nicotine addictions. Finding out how to build resistance to certain compounds, without any ill-effects, could help a lot of people.