Topic overview

Start with the big picture

Opioid receptors are G protein-coupled receptors; their activation decreases cAMP, increases potassium efflux, and reduces calcium influx, thereby suppressing nociceptive transmission. Agents include strong and moderate agonists, mixed or partial agonists, and antagonists. Opioids are used for pain and in selected other settings, while also producing effects such as sedation, miosis, and suppression of cough or gastrointestinal motility. Respiratory depression is a major safety concern; constipation, nausea, and other adverse effects also matter. The topic further introduces tolerance and physical dependence, the characteristic opioid overdose presentation and its management, clinically relevant drug interactions, and precautions in conditions such as severe respiratory disease or head trauma.