While most medications don't affect driving ability, some prescription and over-the-counter (OTC) medicines can cause reactions that may make it unsafe to drive. In New Zealand it is against the law to drive while impaired.
How can medicines affect driving?
Some medicines can cause impaired concentration, inability to focus or pay attention, slow reaction times and cause sleepiness or drowsiness, blurred vision, dizziness, slowed movement, fainting, or excitability. Do not drive if you have any of these symptoms.
Not taking medicines can also be a risk
Not taking some medicines while driving can also be risky, for example:
- Some people with epilepsy may not be able to drive at all without taking their medication.
- For drivers with diabetes, high blood glucose levels can make you feel unwell and tired and may affect your ability to drive. Having high blood glucose levels (hyperglycaemia) because of missed doses of medication or poorly controlled diabetes puts you at increased risk on the road. You should not drive if you have severe hyperglycaemia.
Which medicines are most likely to affect driving?
Always check with your doctor or pharmacist if your medication is likely to affect driving. Some types of medicines known to affect driving include:
- sleeping pills, benzodiazepines
- some antidepressants
- some pain relievers
- some antiepileptic medicines
- some heart medicines
- medicines for diabetes
- some medicines used in the eyes
- anthistamines for allergies
- cold and flu medication
- diet pills, "stay awake" drugs, and other medications with stimulants (e.g. caffeine, ephedrine, pseudoephedrine).
Note: Combinations of medicines and medical problems may affect people differently.
How long should I avoid driving for?
It is important not to drive until you know how the medicine affects you. Some medications only have short-term effects when you change the dose. This means you might only need to stop driving for a few days until your body adjusts. However, some medications are strong enough that you will need to stop driving for the whole course. Learn to know how your body reacts to the medicine and supplements you are taking. Keep track of how you feel, and when the effects occur.
For drivers with diabetes, having low blood glucose levels (hypoglycaemia) is dangerous because it affects concentration. If you are taking insulin or other medicines for diabetes, avoid low blood glucose levels, or if you have frequent 'hypo's, avoid driving until your blood glucose levels are stable.
Alcohol, medications and driving
Drinking alcohol while taking medication or drugs that may impair driving, increases your risk of having a car crash substantially. It can make you 23 times more likely to fatally crash than drivers who have taken none of these. Alcohol can increase the effects of the medicine on your coordination, reaction time, sleepiness, and more. Even though you might be under the legal alcohol limit, you might still be impaired and therefore unable to drive.
Older adults, medications and driving
Medications that cause drowsiness or distraction can impair driving ability, particularly in older people, because of age-related changes in the way the body breaks down medicines. This is of concern because older people often take several medicines to stay well, some of which may affect driving skills. Combinations of medicines can cause unexpected side effects and bad reactions.
Tips for taking medications and driving
- Ask your doctor or pharmacist if the medication you are given may affect driving and if it is safe to drive. Read your medication labels to see if it may affect your driving.
- If you feel that the medication you are taking is affecting your driving, talk to your doctor. They may be able to adjust the dose, adjust the timing of doses or change the medicine to one that causes less drowsiness.
- Consider alternatives to driving such as rides with family and friends, taxi, public buses, trains, or walking.