Which of the following can increase the risk of sedation in a patient receiving meclizine?

Meclizine is an antihistamine commonly used to prevent and treat nausea, vomiting, and dizziness caused by motion sickness. One of its side effects is sedation. Diazepam, a benzodiazepine, enhances the effect of other central nervous system (CNS) depressants, which can include antihistamines like meclizine. When meclizine is taken concurrently with diazepam, the sedative effects can be amplified, resulting in increased drowsiness and sedation.

The other medications listed—ibuprofen, aspirin, and acetaminophen—are analgesics or anti-inflammatory agents that generally do not have sedative effects. While these medications can be important in managing pain or inflammation, they do not typically interact with meclizine in a way that would increase sedation. Therefore, diazepam is the most relevant drug in this context for increasing the risk of sedation when taken with meclizine.