“Just a spoonful of sugar and the medicine goes down,” the old song says. Just a spoonful of medicine at the wrong time, and your car could go down too—down an embankment! Such was the unfortunate reality of Doug, a 56-year-old accountant who had taken an over-the-counter cold medication before driving to visit a client. He didn’t know that the medicine would make him drowsy, until he woke up in his car in a deep ditch by the side of the road.

Many Consumers Unaware of Risks

Most consumers are aware of the dangers of driving under the influence of alcohol or illicit drugs, but many don’t realize that certain prescription and over-the-counter medications can also impair driving. According to the New Mexico Department of Health, certain drugs can interfere with factors that are essential for safe driving, such as:

  • Coordination—needed for steering, braking, accelerating, and manipulating the vehicle
  • Reaction time—needed to respond in time and appropriately deal with certain situations
  • Judgment—helps with risk assessment, avoidance of hazards, and emergency decision-making
  • Tracking—helps to stay in the lane and maintain the correct distance from other cars and obstacles
  • Attention—ability to handle the high demand for information-processing
  • Perception—needed for glare resistance, dark and light adaptation, and dynamic visual acuity

The effects of medications can vary among people. They are often influenced by length of use, tolerance, overall health, individual sensitivity to the drug, metabolism, age, interactions with other medications and other factors. For instance, elderly persons process some medications differently than younger adults, which could cause these drugs to affect them more profoundly.

Use Caution With These Medications

Many medications—particularly those that affect the central nervous system—can impair your ability to drive. They may have side effects such as drowsiness, dizziness, or diminished motor or judgment skills. Such medications may include:

  • Pain relievers with codeine or other opiates (narcotics)
  • Muscle relaxants
  • Sedatives and tranquilizers
  • Anticonvulsants
  • Drugs used to treat high blood pressure
  • Older generation antidepressants, such as tricyclics
  • Over-the-counter medications containing diphenhydramine, brompheniramine, or chlorpheniramine, such as those for:
    • Allergies (antihistamines)
    • ]]>Colds]]>
    • Motion sickness
  • Central nervous system stimulants
  • Herbal remedies that interact with prescription or over-the-counter medications
  • Medications administered to the eye, which can produce heightened light sensitivity


One study in the Annals of Internal Medicine suggested that a standard dose of the antihistamine had a greater negative effect on driving “coherence” than alcohol. Driving coherence is the ability to match the speed of the vehicle ahead to avoid accidents. This study also suggested that antihistamines and alcohol had similar effects on steering ability and the likelihood of crossing into another lane.


Researchers at McGill University in Montreal studied records of nearly 225,000 people age 67-84, and found a 45% increase in injury-causing car accidents in people who had been taking a long-acting group of benzodiazepines. These medications are often prescribed to treat ]]>anxiety]]> or ]]>insomnia]]>. Long-lasting benzodiazepines stay in the bloodstream for more than 24 hours. They include:

Other benzodiazepines are not as long lasting, though shorter-acting benzodiazepines have a strong effect for the first few hours, which can impair driving skills during that time.

Drugs in this group include the following:

Precautions You Can Take

In many states, it is illegal to drive while under the influence of sedating medications. But it’s important to take precautions when taking any medication. Here are some tips:

  • Educate yourself about the side effects of any medication (prescription or over-the-counter) or herbal supplement you take by reading the instructions carefully. Consult with your doctor or pharmacist before taking any new medication, and ask about possible effects on driving and what precautions you should take.
  • If you are taking multiple medications or mixing medications with herbal substances, ask your doctor and pharmacist about possible interactions and side effects that could impair your driving.
  • If you feel that your medication has impaired your ability to drive in any way (you feel dizzy, drowsy, light-headed, “fuzzy,” or are having visual problems, etc.), have someone else drive.
  • If you plan on driving, look for over-the-counter medications that do not cause drowsiness or other side effects that could impair driving.
  • Ask your doctor if there is an alternative to any prescription medication that is impairing your ability to drive.
  • If you're taking long-lasting benzodiazepines for insomnia or anxiety, talk with your doctor. You may want to switch to another medication that isn't linked to a higher risk for accidents. However, you should never stop taking your medication without talking to your doctor first. Stopping these drugs suddenly can, in some instances, cause seizures, extreme anxiety and other serious problems.