What is a common side effect of opioids?

Opioids are well-known for their effects on the gastrointestinal system, and one of the most common side effects associated with their use is constipation. This occurs because opioids bind to receptors in the gastrointestinal tract, which slows down peristalsis and decreases bowel motility. As a result, patients often experience difficulty with bowel movements, leading to constipation.

While nausea can also occur with opioid use, it is not as commonly experienced as constipation. Insomnia may arise due to an assortment of factors in patients who are on opioids, but it is not a direct result of the medication itself. Diarrhea is often the opposite effect of what opioids cause; typically, opioids will lead to less frequent bowel movements rather than more. Therefore, constipation stands out as the most prevalent side effect of opioids, making it the correct choice in this scenario.