Which of the following medications can cause sedation as a side effect?

Antihistamines are known to cause sedation as a common side effect, particularly the first-generation antihistamines such as diphenhydramine. These medications work by blocking histamine receptors in the brain, which can lead to drowsiness. This sedative effect is often utilized in over-the-counter sleep aids or for the treatment of allergies when sedation is considered a beneficial side effect.

In contrast, acetaminophen is primarily an analgesic and antipyretic with minimal sedative effects. Albuterol, a bronchodilator, is designed to open airways and does not typically cause sedation; its primary side effects may include tremors or increased heart rate. Metformin, used for managing type 2 diabetes, is not associated with sedation either; its common side effects are gastrointestinal, like nausea and diarrhea. Thus, antihistamines stand out as the medication group here that is recognized for causing sedation.