This year marks the introduction of a new set of drug driving laws that cover legal limits for various drugs and prescription medication. From March 2, it will become an offence to drive with more than the legal limit of certain drugs in one’s bloodstream, but which drugs come under this new law and how might it affect you?

Why is the law changing?

The law has been brought in to ease the police force’s detection and arrest of those putting lives at risk on the road, driving under the influence of drugs. Previously, the laws in place only specified against drug-impaired driving, with no limits in place for illegal drugs or prescription drugs, in spite of the potential for abuse. This ambiguity made prosecution of offenders difficult and crimes harder to prove.

With the new laws in place, a zero tolerance policy shall be enforced when dealing with illegal substances, with very low ‘trace amount’ limits in place for these drugs. Conversely, legal medication will have a much higher limit, at levels generally attributed to abuse or overdose.

Police are also to use new ground-breaking “drugalysers” which can analyse saliva samples on the roadside to give any readings for cannabis and cocaine. This will eliminate the need for police to obtain permission for more invasive measures such as urine or blood samples, which can waste time and allow drugs to leave an offender’s system.

I take prescription medication, will this affect me?

It is understandable to feel concerned if you are prescribed any medication, but the majority of patients will not be affected by these changes. The amount of any drug present in the body depends on a number of variants: the amount prescribed, how long the body takes to eliminate the drug, and any other medication or substance present in the body that could interact with the drug. Anyone who decides to participate in recreational drug use will find themselves affected by this law. The tools now in place to detect drugs are ever more effective and the limits do not allow for more than trace amounts of drugs to be present in one’s system. Though refraining from using illegal drugs is always advised, it’s crucial not to drive if under the influence of any illegal substance, no matter how in control you may feel at the time.


Those suffering from chronic pain or prescribed pain medication will need to discuss with their doctor how they may be affected by this law. It is unlikely that you will be over the legal limit unless you are a long-term user of pain management medication or suffering from pain that is not treatable with normal doses. You may have been advised not to drive when prescribed the following medication, but it’s important to make sure you are fully informed on what you are taking and how you may be affected.

Those who may be recovering from opiate addiction could be affected by the new laws, as drugs commonly used to treat addiction and aid rehabilitation are included in the changes.

While most people undergoing this type of treatment are generally on short-term plans, there may be those using the medication for a longer period of time. If this applies to you, it is important that you discuss the drugs you are prescribed thoroughly with your doctor or primary care physician and keep evidence of your prescription close to hand when driving.


Benzodiazepines are commonly used to treat anxiety disorders in patients who haven’t responded to other treatments, or can be used for atypical situations (e.g. someone with a severe fear of flying may be prescribed a small amount ahead of a long-haul trip).

It is known that this medication can cause drowsiness, and your doctor should always discuss the dangers of driving whilst taking benzodiazepines. Anyone using this medication on a regular basis may still be driving depending on their dosage, tolerance and personal circumstances, so it’s important that you understand how your dosage may affect you.

What happens if I am over the limit?

The legislation provides a statutory “medical defence” for anyone taking certain drugs for medical reasons, providing that their driving was not impaired. A medical defence applies if the medication was prescribed or sold to treat a medical or dental problem, and was taken in line with the information or instructions given to them.

The individual may need to provide written evidence, such as a prescription receipt or the information leaflet that accompanied the medication. However, the medical defence would not apply if an individual’s driving was found to be impaired by any substances. This is already covered in existing laws and will remain an offence in future.

Solicitor Jessica Gower, of personal injury specialists Neil Hudgell Solicitors, said: “As a nation of drivers we all have a duty to ensure that we do not pose a danger to either ourselves or any other member of the public before we commence and whilst we continue our journeys. This has to include checking the side effects of any prescribed medication, and if in doubt avoiding driving whilst the advice of a medical practitioner is sought. It is simply unacceptable to get into a vehicle without having done so.

“It takes a split second to knock someone from a bicycle or to hit a pedestrian, causing devastating and often fatal injuries. Driver’s response times to prevent such life changing events are often minimal and so a zero tolerance approach must be adopted towards those who negligently or knowingly impair their judgement through the use of drugs.”