Final answer:
To reduce rebound congestion caused by phenylephrine nasal spray, the nurse should instruct the client to decrease the frequency of use to twice daily. Discontinuing the use or adding oxymetazoline nasal spray will not effectively address rebound congestion.
Step-by-step explanation:
To reduce rebound congestion caused by phenylephrine nasal spray, the nurse should include the instruction to decrease the frequency of use to twice daily (option A). Rebound congestion occurs when the nasal passages become congested again after the effects of the medication wear off. By reducing the frequency of use, the client can help prevent this rebound effect. It is important to note that the nurse should not instruct the client to discontinue the use of the nasal spray fully, as this may lead to worsening congestion. Adding oxymetazoline nasal spray (option D) may help relieve symptoms in the short term but will not address the underlying issue of rebound congestion.