Which of the following is a side effect commonly associated with opioids?

Nausea is a commonly recognized side effect of opioids due to the way these medications interact with the central nervous system. Opioids work by binding to specific receptors in the brain and spinal cord, which can affect not only pain perception but also gastrointestinal motility and the area of the brain that controls nausea and vomiting. As a result, many patients taking opioids may experience nausea, particularly when they start treatment or when their dosage is adjusted.

The other options do not align with the typical side effects of opioid medications. Hypertension is not a common side effect of opioids; in fact, opioids may actually cause hypotension in some cases. Increased appetite is generally not associated with opioid use, as these drugs are more likely to lead to decreased appetite. Lastly, opioids are known to cause sedation rather than increased alertness, as they often induce drowsiness or lethargy.