Britannica Sources used in this answer

Why can sedating antihistamines impair driving performance?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

antihistamines, including Benadryl — antihistamine Antihistamines such as Benadryl (diphenhydramine) and Claritin (loratadine) can be purchased without prescriptions. Both of those agents act by blocking H₁ receptors. However, whereas Benadryl binds to those receptors in the central nervous system (CNS), causing drowsiness, Claritin does not readily enter the CNS and thus does not normally cause drowsiness.

Sedating antihistamines can impair driving performance primarily because they possess sedative properties that affect the central nervous system.1

These medications, particularly older H1 receptor antagonists, bind to receptors in the brain and induce drowsiness. Because of this sedative action, they can reduce alertness and reaction times, which are critical for safe driving. Furthermore, these drugs can enhance the effects of alcohol and other depressant substances, further compounding the risk of impairment.1

It is important to prioritize safety by being aware of how these medications affect your ability to operate a vehicle. If you are taking a medication that causes drowsiness, you should refrain from driving to protect yourself and others on the road.