We hear a lot about opioids, especially in USA and Canada, where despite their high risk of addiction and overdose , these moderately strong painkillers have become popular both as formal medical treatments and as recreational drugs.   But what do they actually do, and how can they cause death? In a fatal overdose, people often die because they can’t breathe…the drug suppresses brain activity that controls breathing rate, lung expansion, and carbon dioxide monitoring.

More on Scientific American here