Final answer:
The nurse should teach the client to monitor for constipation as a side effect when taking codeine sulfate to suppress a nonproductive cough.
Step-by-step explanation:
The nurse should teach the client to monitor for the side effect of constipation when taking codeine sulfate to suppress a nonproductive cough. Codeine is an opioid medication, and constipation is a common side effect of opioids. The drug acts by binding to opioid receptors in the gastrointestinal tract, which slows down intestinal motility and can lead to constipation.