Final answer:
The nurse practitioner should inquire if the patient takes any medication for depression or anxiety before recommending dextromethorphan, as certain antidepressants can interact negatively with this medication.
Step-by-step explanation:
When considering whether a patient can take dextromethorphan (Robitussin) for cold symptoms, it is especially important for a healthcare provider to inquire about the patient’s current medication regimen. The most relevant question for the nurse practitioner to ask in this case is: "Does the patient take any medication for his depression or anxiety?" Since certain antidepressants can interact negatively with dextromethorphan, leading to a potentially dangerous condition known as serotonin syndrome, this information is crucial.
Other factors such as nausea and vomiting, smoking habits, or GI complaints, while important in a general health assessment, are not as directly related to potential drug interactions with dextromethorphan.