Which type of over-the-counter medication is most likely to cause drowsiness in drivers?

Antihistamines are known for their ability to block histamine receptors in the body, which can lead to sedative effects. This is particularly true for first-generation antihistamines, such as diphenhydramine (found in Benadryl), which can cross the blood-brain barrier and affect the central nervous system, leading to drowsiness and a reduced ability to concentrate. Since driving requires full attention and responsiveness, using antihistamines can significantly impair driving ability.

In contrast, pain relievers, while they can also have side effects, are less likely to cause drowsiness compared to antihistamines. Antibiotics primarily treat bacterial infections and do not typically produce sedative effects. Cold medications might contain various active ingredients, some of which may not be sedative. However, many cold medications also include antihistamines, so they can sometimes lead to drowsiness, but without sedatives specifically mentioned, they are less likely to be the main cause of drowsiness compared to antihistamines alone.