WASHINGTON—The increasing use of legal and illegal medications by drivers and pilots has prompted the National Transportation Safety Board to recommend a greater study of drug use and more education for vehicle operators.
Evidence of impairing medications was found in 22 percent of non-commercial drivers tested randomly across the country in a recent study conducted by the National Highway Transportation Safety Administration (NHTSA). Nearly half of the detected drugs were legal prescription medications or over-the-counter (OTC) products.
Five classes of legal but impairing medications were found more often than “illicit drugs” in a 2014 study of pilots fatally injured in air crashes.
“The important thing is, professional drivers of motor vehicles need to be aware of what we are being given,” said Nicholas Webster, M.D., medical officer of the National Transportation Safety Board.
While opioid abuse is on the rise, he said, “The most common drug found in pilots was diphenhydramine — the ingredient in Benadryl. It also is found in many over-the-counter cough and cold medications. Because it is sold over the counter, people think it is okay. It is not.”
He described a study that tested people in a driving simulator after one dose of diphenhydramine. “Their driving was actually worse than when a driver is impaired by alcohol at a level of .10 percent — .08 is currently considered legally intoxicated in all 50 states.”
Many types of drugs may cause impairment and reduce driving safety, Webster said. “An impairing drug is any one that makes you sleepy or alters your ability to think or react normally.”
On Oct. 16, the NTSB ruled that a drug-impaired pickup truck driver was the primary factor in a 2017 church shuttle bus collision near Concan, Texas, that killed 13 people. Toxicology tests determined the truck driver was impaired by clonazepam, a sedative used to treat seizures, panic disorders and anxiety.
The truck driver had been prescribed this drug, which can cause drowsiness, but had taken a double dose an hour before the crash. The tests also found evidence of marijuana use.
One result of the Concan investigation was a recommendation that all states issue guidelines to health care providers who prescribe medications, particularly for controlled substances that treat pain.
“We recommend that health care providers discuss with patients, especially patients who are commercial operators, the effects of their medical conditions and medications on their ability to safely operate a vehicle in any mode of transportation,” Webster said. “As you know, there is an opioid crisis now. Many opiates are impairing. We definitely want our drivers to understand how these drugs affect them and the way they control their vehicles.”
The NTSB study of pilots noted that many operators are not aware of the risks of using some medications or the availability of safer substitutes. “There are alternatives to diphenhydramine such as fexofenadine (commonly marketed with the brand name Allegra) and loratadine (commonly marketed with the brand name Claritin) that do not have the same potential for impairment.”
The study added, “Consumers may not be aware of less impairing alternatives; one study found that only one if five adults reads label warnings when buying an OTC drug for the first time.”
Accurate estimates of medication usage among commercial vehicle operators or other drivers are not known, Webster said. “Testing varies from state to state. In the Concan accident report we made recommendations that NHTSA develop and disseminate to state officials a common standard and practice for toxicology testing, including the circumstances under which drug testing should be conducted, a minimum set of drugs for which to test and cut-off values.
“We are concerned that in the fatal motor carrier crashes we are not getting adequate testing so we can understand the extent of what is going on and the science behind drugs and people driving commercial vehicles or any vehicle,” he said.
When differences in testing procedures were taken into account, the NHTSA driver study found that 3.7 percent more drivers were positive for illegal drugs or medications in 2014 than in 2007.
The NTSB aviation study found that the proportion of pilots with at least one positive drug finding increased from 10 percent in 1990 to 40 percent in 2011. Use of sedating antihistamines and diphenhydramine by pilots doubled from the 1990s to 2012. Cardiovascular drug usage increased from 2.4 percent to 12.4 percent.
“We can say, in general, the use of impairing and non-impairing drugs is going up within the country,” Webster said.
Both studies emphasized that a drug’s presence does not indicate a pilot or driver is impaired. “Most psychoactive drugs are chemically complex molecules whose absorption, action and elimination from the body are difficult to predict, and considerable differences exist between individuals,” the NHTSA report explained.
The aging of the population is one reason for the increase in medication usage, Webster said. “As we get older, some of us develop medical conditions that can require medications, but that doesn’t mean that older people have a higher risk of using impairing medicines. A young person can be just as likely to have a medical or psychiatric condition that requires treatment.”
Positive Drug Findings in Fatally Injured Pilots
2008-2012
Cardiovascular Drugs 12.4%
Sedating antihistamines 9.9%
Non-sedating OTC drugs 7.3%
Anti-depressants 5.3%
Sedating pain relievers 4.4%
Illicit drugs 3.8%
Benzodiazepines 2.0%
Cholesterol lowering drugs 2.0%
From Drug Use Trends in Aviation: Assessing the Risk of Pilot Impairment, NTSB, 2014
