AEMCA Practice Exam

Diphenhydramine is known for its sedative effects primarily because it is an antihistamine that can easily cross the blood-brain barrier. This ability allows it to interact with receptors in the central nervous system, leading to drowsiness as a common side effect. Antihistamines like diphenhydramine are primarily used to relieve allergy symptoms, but their sedative properties make them a choice for treating insomnia or for reducing anxiety in some cases.

In contrast, salbutamol is a bronchodilator primarily used for asthma and does not produce sedative effects. Epinephrine, a hormone and neurotransmitter, is typically utilized in emergency situations, especially for anaphylaxis, and its effects are more stimulatory than sedative. Aspirin is a non-steroidal anti-inflammatory drug (NSAID) used to relieve pain and reduce inflammation and does not cross the blood-brain barrier in a manner that would lead to sedation. Therefore, diphenhydramine stands out as the medication that notably causes sedation due to its ability to penetrate the central nervous system.