News stories of celebrities being jailed for driving under the influence of recreational drugs may seem to be in a different world from your school run or trip to work. But that's the core of a largely misunderstood danger to road users. It's not just illegal drugs that can get you into trouble on the roads; prescription and over-the-counter (OTC) drugs can, too.

The problem is that many pharmaceuticals can cause drowsiness, impair your concentration or increase your reaction times - and perhaps all three. Any of these side effects can impact on your driving ability.

You could be breaking the law

In the UK, driving whilst under the influence of any drug is a serious offence. It doesn't matter if they have been prescribed by your doctor, the Road Traffic Act 1988 says that you mustn't drive under the influence of drugs or medicine. Similarly, in the US, you could be charged under Driving Under the Influence (DUI) legislation. And, throughout Europe, regulations tend to group driving under the influence of prescription drugs along with driving under the influence of alcohol or illegal/recreational drugs.

You shouldn't be under the misapprehension that a motoring offence committed under the influence of prescription or OTC drugs will be treated leniently. The police and the courts take a dim view of drivers who cannot control their vehicles.

Common medicines you should look out for

This isn't a comprehensive list, but you should certainly be careful to make sure you're not affected by the following types of medication - cough remedies, cold and flu treatments, pain killers and anti-histamines. Even some eye drops can make you feel drowsy by affecting your central nervous system.

Read the leaflet

It's sensible to read the leaflet that's included with almost all medicines. If the drug is likely to cause drowsiness while driving, there will be a warning, but it may be buried in amongst a lot of other information. Unfortunately, it's up to you to read the leaflet right through and satisfy yourself that there is or isn't a warning. It's your legal duty to be aware of the risk, and ignorance will not be accepted as an excuse in court.

If taking a drug with a driving warning is going to be inconvenient for you, don't take the risk of taking the treatment, but discuss any alternatives with your GP or your pharmacist. There could well be another alternative that will not interfere with your driving.

Other pitfalls

Mixing even small amounts of alcohol with certain drugs can seriously harm your ability to drive. Even if you're under the drink-drive limit, you could still find yourself prosecuted. And be careful if you if you take medications in the evening or during the night, their effects may continue on through the day as well. If you feel drowsy, light-headed or otherwise less sharp than you would expect, do not drive until you have checked with your doctor.

If you have been prescribed more than one medication, you may find they interact to cause drowsiness, even if none of them have a drowsiness warning. Again, if you feel affected and unsure of your ability to drive, seek the advice of your doctor or pharmacist.

Finally, if you are coming towards the end of a course of treatment that has caused you to feel this way, you shouldn't immediately return to driving. Seek guidance from your doctor before getting behind the wheel.

The message is to be very careful of the effects of prescription and OTC medications because the buck stops with you, the patient and driver if you get into trouble or are have an accident. You could well be seen as responsible for the outcome.