Medicines affecting the ability to drive

Updated 13 April 2012

Drugs affecting the ability to drive, what are they?

Drugs affecting the ability to drive have a sedative effect on the central nervous system, causing you to:

  • become drowsy or sleepy
  • find it hard to concentrate
  • react more slowly than you normally would
  • feel under the influence.

Most people know that alcohol and driving is a bad mix. But not as many would think that the combination of certain types of medicines and driving could be just as dangerous.

Like alcohol, "drugs affecting the ability to drive" can have a sedative effect or make you feel tipsy and could affect your judgement and your ability to react. The effect of taking these medicines is easily comparable to having a blood alcohol level, which means that it could increase the risk of accidents considerably.

Therefore, be extremely cautious if you drive or use machines while taking a medicine with a red warning triangle.

Red warning triangle tells you which drugs affect your driving ability

In Denmark, medicines that are associated with the highest risks of affecting you are labelled with a red warning triangle.

It indicates that the medicine causes drowsiness, and that it can affect the safety of work and the ability to drive.

But it is very important to be aware that there are medicines without the red warning triangle that can also affect your ability to drive safely, as we will describe below.

Drugs affecting the ability to drive – three degrees

In Denmark, the Danish Medicines Agency assesses if a drug is to be labelled with a red warning triangle to indicate that it affects the ability to drive.

The Danish Medicines Agency evaluates the medicine's effect and side effects and also considers if it is a medicine that you take yourself or if it is given by a doctor, for example as part of surgical procedures.

Only those medicines that you take yourself are labelled. The doctor who gives you a drug (while in hospital, for example) will tell you if it affects your ability to drive.

When the Danish Medicines Agency has finished its assessment, it decides which of the following three degrees the medicine should have.

  • No impairment - mild impairment
  • Small impairment - moderate impairment
  • Significant impairment

Only those medicines that impair the ability to drive significantly are labelled with a red warning triangle

The warning triangle is used in Denmark, Norway, Finland and Iceland, so it is not an internationally used symbol.

If you buy medicine abroad, the medicine will probably carry a different warning label.

Which medicines bear the red warning triangle?

In Denmark, the following types of medicines carry the red warning triangle, but the list is not complete.

  • strong and certain mild painkillers
  • medicines for epilepsy
  • medicines for anxiety
  • tranquillisers
  • cough remedies
  • motion sickness medications
  • anti-nausea medicines
  • allergy and hay fever medicines
  • migraine tablets
  • certain weight-loss products
  • medicines for ADHD
  • any medicine that contain more than 10 % alcohol
  • sleeping tablets (do not drive until your body has excreted the drug)

Not all drugs affecting the ability to drive have a red warning triangle

In special situations, some medicines without a red warning triangle could still affect work safety and your ability to drive.

Always read the package leaflet with the medicine. It tells you about any precautions that you should take. Think twice if the medicine you are taking in some way makes you feel impaired.


  • Eye drops which contain substances that dilate the pupils could impair your vision.
  • Medicines for high blood pressure can cause dizziness, discomfort and could thus impair your ability to react.
  • Insulin and medicines for diabetes may indirectly impair your ability to react. If you take too much medicine, your blood sugar could drop too low, and you can get dizzy and feel unwell, which means that your ability to react is impaired.
  • Medicines for hay fever and allergy can affect your ability to react, so it's important that you pay attention to how you feel. Hay fever in itself can cause sleepiness and thus impairs your ability to react.
  • Dry cough medicines. These medicines affect the central nervous system, which means that they can make you drowsy.
  • Medicines for depression or other psychiatric disorders.
  • Several types of herbal remedies can also cause drowsiness and thus affect your ability to react. In particular, you should be aware of medications that contain valerian.

Special requirements for certain occupational groups

You should be aware that some drugs affecting the ability to drive are considered so dangerous by some industry organisations/employers or the Danish Transport Authority that you are not allowed to take them while you work, no matter that the medicine is not labelled with the read warning triangle. If you're not sure whether your medicine is affected, check this with your industry organisation.

Take a note of how you react

When you take a medicine for the first time or if you take more medicine than you normally would, be very careful about deciding to drive.

If you feel unwell, drowsy or exited shortly after you have started taking a new medicine or if you have changed the dose, the medicine may affect your ability to drive.

The effect could be short-term or might not show until after a while, but either way, it is crucial that you pay attention to how you react. Remember that we all respond differently to the same medicine!

How strong is the medicine's effect?

It depends on how much medicine you take. We cannot say for certain how you will react as people respond differently to medicine. Factors such as gender, age, weight and dose all play a part in how the medicine will effect you.

Usually, the sedative effect is strongest in the beginning of treatment and when the dose is increased.

If you take more than one medicine or take any of them with alcohol, sometimes the sedative effect will increase.

Drugs affecting the ability to drive and alcohol

If you take medicines with alcohol, the alcohol may increase the sedative effect of medicines that affect the ability to drive. The sedative effect can also increase if you take several medicines that bear the red warning triangle at the same time.

Check your medicine before you get behind the wheel

  • You should check with your doctor or pharmacist if your particular medicine could affect your ability to drive.
  • Always see if your medicine bears the red warning triangle, and stay alert!
  • If you start on a new medicine that has the red warning triangle, or if your dose of your usual medicine is changed, it is important that you do not drive until you know how it effects you.
  • Remember to read the package leaflet. The package leaflet tells you about the medicine's side effects and what the effects are if you take more than one medicine or if you take it with alcohol.
  • If you start taking a medicine for psychiatric disorders, diabetes, or high blood pressure, or if the dose of your medicine is changed, check with your doctor if you shouldn't drive at all.
  • Never mix alcohol with a drug that affects the ability to drive. Even one single glass of beer or wine increases the sedative effect significantly.
  • Remember also that medicines without the red warning triangle could affect how you go about in traffic. Therefore, it is always a good idea to see how new medicine affects you before you go flying into traffic.

The package leaflet and summary of product characteristics describe issues with driving safely

Information about the medicine's effect on the ability to drive is included in the summaries of product characteristics and the package leaflet for all medicines. The information is most often based on the available standard sentences.

These sentences are to help the doctor and patient decide how to ensure utmost safety for the patient when using the medicine.

It is therefore always a good idea that you to read the package leaflet before you take your medicine and before you hit the road. The package leaflet also describes what side effects the medicine could give.

As mentioned earlier, some of these side effects could affect your ability to drive safely. If you have lost the package leaflet, you can always find the most recent one at indlæ (in Danish only).

List of drugs affecting the ability to drive

List of drugs affecting the ability to drive (updated daily)

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