Why is it so hard to create new types of pain relievers?

This article first appeared in The Checkup, MIT Technology Review’s weekly biotech newsletter. To receive it in your inbox every Thursday, and read articles like this first, sign up here. This week I’ve been thinking about America’s addiction to opioids. The statistics are staggering. Since 2010, opioid overdose deaths have nearly quadrupled. More than 80,000 people…