What are depressant effects of opioids?

• A. Decreased coughing only
• B. Decreased breathing, constipation, sedation, decreased cough
• C. Increased respiration and alertness
• D. No effect on respiration

Answer: (B)

Opioids act as central nervous system depressants, especially on areas that regulate breathing, gut motility, arousal, and coughing. The hallmark depressant effects are slowed breathing (respiratory depression), slowed intestinal transit leading to constipation, sedation or drowsiness, and suppression of the cough reflex. This comes from mu-opioid receptor activation in the brainstem: reduced responsiveness of the respiratory center to CO2 causes hypoventilation; activation in the medullary cough center dampens coughing; decreased GI motility and increased sphincter tone produce constipation; and overall CNS depression leads to sedation. The combination of these effects is why the description including decreased breathing, constipation, sedation, and decreased cough best matches opioid depressant effects. In contrast, increased respiration and alertness would be stimulatory, and saying there’s no effect on respiration conflicts with the primary danger of opioid overdose. A description limited to decreased coughing misses several key depressant effects.