Opioids are powerful painkillers, but their use is hindered because patients become tolerant to them, requiring higher and higher doses, and overdoses can cause respiratory depression and death. A recent study from researchers at the UC Davis Center for Neuroscience contradicts existing thinking about how opioid drugs cause tolerance and respiratory depression, and suggests a new, balanced approach to developing safer analgesics. The work was published July 13 in Neuropsychopharmacology.