Driving under the Influence

Driving while drunk is dangerous, not news to most people.  However many people are surprised that many over the counter medicines like Benadryl (diphenhydramine) make people dangerous drivers as well.

 Years ago a group of people were given a simulated driving test.  Some took cold medicine like Benadryl and others were made legally drunk. (If memory serves, with great effort they found a bunch of college students and paid them). The people that took Benadryl were actually worse drivers, partly because they didn’t know they were impaired.  They thought they were fine. The effects lasted about 4 hours, longer than for many of the drunk drivers.

 So if you take a medicine like Benadryl you will be considered to be “driving under the influence” in many states.  So impaired and committing a crime.  Certainly you are at risk to have an accident.  That is why this medicine is also banned for pilots.

 Many prescription medicines should not be used while driving or while working.  These include narcotics and many anxiety medicines like Xanax or Valium.

 Driving while being very tired has been shown to be as dangerous as being drunk.  People with uncontrolled sleep apnea tend to have more car accidents than normal people.  Truck drivers and pilots have strictly enforced rest periods because of this danger.

 In all of these cases people do not realize their driving has worsened.  They respond to emergencies slowly, drive too fast or slow and interpret simple signs and stoplights incorrectly.   Many people tell me they are good drivers.  Even good drivers may not know they have taken a medicine that made them poor drivers.  

 So… if you drive, don’t drink and avoid medicine either prescription or over the counter that can make you sleepy.  If you haven’t slept much in the last 24 hours, don’t drive.

 Gengo FM, Manning C. A review of the effects of antihistamines on mental processes related to automobile driving. J Allergy Clin Immunol 1990;86:1034-9.