Opioid drugs are highly effective at relieving pain but come with severe drawbacks. Their side effects range from dizziness to potentially fatal respiratory depression. Their illegal use contributes to nearly half a million deaths worldwide each year. Researchers have discovered a molecule, called nanobody NbE, which binds tightly and durably to the cell receptors that usually bind to opioids, thereby blocking the drugs’ activity. Moreover, the scientists were able to create even smaller molecules that retain the same properties, which could prove far more effective than current treatments in mitigating the harmful effects of opioids.