Which of the following medications is specifically categorized as a 1st-generation antihistamine?

1st-generation antihistamines are primarily characterized by their ability to cross the blood-brain barrier, often resulting in sedative effects. Promethazine is a classic example of a 1st-generation antihistamine. It is commonly used for its antihistaminic properties as well as its effectiveness in preventing nausea and motion sickness due to its central nervous system effects.

In contrast, the other options listed are 2nd-generation antihistamines. Fexofenadine, cetirizine, and loratadine were developed to have fewer sedative effects, as they are less likely to penetrate the central nervous system. This distinction is crucial in selecting antihistamines for specific clinical scenarios, particularly when sedation is undesirable. Promethazine’s sedative properties and broader therapeutic uses demonstrate the distinct nature of 1st-generation antihistamines compared to their 2nd-generation counterparts.