Which of the following antihistamines is the least likely to induce drowsiness?

Explanation

Among the listed antihistamines, Promethazine, Diphenhydramine, and Hydroxyzine are known to cause sedation due to their ability to cross the blood-brain barrier. Loratadine, however, is a second-generation antihistamine that does not readily enter the central nervous system, making it the least sedating option.