Which of the following is a major adverse effect of opioid analgesics?

• A. Headache
• B. Nausea
• C. Respiratory depression
• D. Hyperglycemia

Answer: (C)

Opioid analgesics depress respiration by acting on mu receptors in the brainstem’s respiratory center, reducing the ventilatory response to carbon dioxide. This makes breathing slower and shallower, which can progress to hypoventilation and hypoxia. Because breathing suppression poses the greatest risk to life, respiratory depression is the major adverse effect to watch for with opioids. Headache isn’t a typical major opioid effect, nausea is common but not as dangerous, and hyperglycemia isn’t associated with opioid use. In practice, monitor breathing pattern and oxygenation, assess level of sedation, and be prepared to use naloxone if respiratory depression occurs, while ensuring airway safety.