Effects of Drugs and Medication on Driving

All drugs cause side effects that are incompatible with driving an automobile. The same is true for some types of medication.

There are no harmless drugs

All drugs, from cannabis to cocaine, act on the brain and hinder your ability to drive, even if you have the impression that you can no longer feel the effects of the drug you used.

“Hard” drugs

These drugs include LSD, cocaine, crack and heroin, to name a few. They have an immediate and significant effect on the central nervous system. In most cases, they cause feelings of overexcitement, energy and euphoria that may make a person feel invincible.

When used at the wheel, hard drugs can turn drivers into highly dangerous individuals. Excessive speeding and recklessness can result in traffic accidents that often involve not only twisted metal, but lost lives.

“Soft” drugs

Smoking cannabis or using it under any other form causes effects that are as dangerous as using hard drugs, because the THC contained in this drug also acts directly on the central nervous system (the brain).

Cannabis at the wheel causes a decrease in vigilance and concentration, slower reflexes, poor coordination, longer reaction times, and impaired judgment.

When driving under the influence of cannabis, you could:

  • Fail to notice road signs
  • Veer off the road
  • Have difficulty maintaining a constant trajectory
  • Pass other vehicles in an unsafe manner
  • Take too long to brake
  • Have difficulty reacting in the case of an emergency

Prescription and over-the-counter medication

Some medications prescribed by health care professionals or sold over the counter can affect your ability to drive because they may cause:

  • drowsiness
  • dizziness
  • blurred vision
  • decreased concentration
  • memory problems
  • etc.

These medications can include tranquilizers, antidepressants, sleeping pills, antihistamines (for allergies), decongestants (for sinus problems or coughing, etc.), muscle relaxants and others, such as painkillers that contain opioids or other substances.

Almost all types of medications can cause side effects that affect your ability to drive, and these side effects may vary from person to person. Medications that cause drowsiness are particularly dangerous when driving.

You take medication and you have to drive?

Consult your physician or pharmacist to know about the effects of your medication on driving.

Carefully read the instructions and pay special attention to any contraindications to driving, regardless of whether the medication is prescribed by a physician or sold over the counter.

Beware of mixing!

Mixing medication with alcohol or drugs considerably increases your risk of being involved in a fatal accident. The effects of the different substances used can add up and amplify each other.

Simple and effective alternative solutions

Only time can eliminate the effects of drugs and medication, so plan accordingly! To get around, you can:

  • ride in a taxi, use a rideshare service or take public transit
  • have a designated driver for the evening
  • sleep over
  • call a drive-home service, such as Operation Red Nose or Tolérance Zéro.

A pact for life

Sign a pact for life (PDF, 356.9 ko)This file does not meet the Web accessibility standard. (available in French only) with your friends or family. In the pact, each person promises not to drive while impaired and offers their services to go and get the other person at any time.

Last update: June  3, 2022