Which of the following is an indication for dimenhydrinate administration?

Dimenhydrinate is an antihistamine commonly used to prevent and treat nausea and vomiting, particularly those associated with motion sickness or vertigo. Its primary action is to block the signals to the brain that trigger the vomiting reflex. Given this mechanism, the administration of dimenhydrinate is primarily indicated when a patient is experiencing nausea or vomiting.

The other options do not align with the indications for dimenhydrinate. Severe headaches may require different treatments focused on analgesics or other specific medications rather than an antihistamine. Chest pain could suggest a range of serious conditions, such as cardiac issues, which would require urgent evaluation and intervention rather than dimenhydrinate. Similarly, difficulty breathing could indicate conditions such as asthma or an allergic reaction, necessitating medications like bronchodilators or epinephrine rather than dimenhydrinate. Thus, the indication for dimenhydrinate is clearly related to its effectiveness in addressing nausea and vomiting.