Substances Other Than Alcohol, Like Cannabis, Can Impair Driving

Rutgers poison control experts discuss legal substances beyond alcohol that can impair driving

With the recent legalization of marijuana sales in New Jersey, poison control experts are reminding drivers that legal medicines and substances such as cannabis can make driving unsafe.

“It’s widely known that alcohol use affects a person’s ability to drive, but many everyday products and substances cause serious side effects that make drivers feel different when they’re behind the wheel,” said Diane Calello, the executive and medical director of the New Jersey Poison Control Center, a division of the department of emergency medicine at the Rutgers New Jersey Medical School.

Calello discussed substances that people should use with caution when driving.

What substances other than alcohol can affect your ability to drive?

Typically, when people hear the phrase “driving under the influence,” they think of alcohol and drunk driving. However, many products greatly increase the risk of driving under the influence, including prescription drugs, over-the-counter medicines, recreational drugs, illegal or street drugs and medicinal and recreational tetrahydrocannabinol (THC) or marijuana. These substances can cause effects like extreme sleepiness, loss of focus or attention, decreased coordination, blurred vision and slow reaction times, which make driving unsafe.

People are surprised to learn that many of the medications they regularly take can affect their ability to drive safely, including antiseizure medicines, sleeping aids, muscle relaxants, antidiarrhea medicines, anxiety drugs, antidepressants, pain medicines, allergy products, antipsychotic medicines, cough and cold products, diet pills and motion sickness medicines.

How can marijuana affect driving?

Marijuana could impair your judgment, motor coordination and reaction time. Some studies have found a direct relationship between blood THC concentration and impaired driving ability, though more research is needed.

In New Jersey, driving under the influence of marijuana is illegal. Currently, there is no defined legal limit to determine marijuana-impaired driving or clear guidance as to how long a person should wait before driving after using marijuana. If you are using marijuana, do not drive in New Jersey. Arrange for a ride with someone who has not been using any substances or call a taxi or ride service.

What do you want people to know about taking medications and driving?

Until you know how a prescription drug or over-the-counter medicine affects your driving, do not drive. Many products warn about the potential for impaired driving. If a label says “Do not operate heavy machinery,” that includes your car.

Be knowledgeable about active ingredients in medicines, possible side effects and potential interactions. Before using, read the product’s label for warnings, directions and ingredient list. Dangerous interactions can still happen even if the products were taken at different times. It’s also important to realize that more does not mean better: Do not take medicines longer or in higher doses than the directions recommend. If symptoms continue, see your doctor. Measure dosage with a measuring spoon, dosing cup or oral syringe – not a kitchen spoon.

Use medicines that treat only the symptoms you have. For example, if you are congested and do not have other symptoms, use a decongestant product only. If you are congested and have a cough, use a decongestant product that also stops coughing. 

Limit or avoid using alcohol when taking medicine. Many ingredients used in medicine can interact dangerously with alcohol, causing effects such as nausea, vomiting, drowsiness, fainting and loss of coordination. Your pharmacist, health-care provider or the medical staff at the New Jersey Poison Control Center can help in choosing medicines that will not interact with the medicines you are already taking.