Drug driving laws and codeine

New regulations come into force in England and Wales today regarding driving under the influence of drugs.  These changes to the law came about because of campaigns following a number of tragic deaths caused by drivers under the influence. Enforcement of the regulations is made possible by the approval of a roadside test that can detect traces of drug in saliva. The test is based on the binding of the drug to a highly specific protein called an antibody, that then causes a colour change. (The device works in a similar way to a pregnancy test kit which detects diagnostic hormones in urine). A positive road-side drug’s test is only preliminary and a further blood test is necessary for confirmation in order to prosecute.

Most would argue that prosecution for driving under the influence of illicit drugs is a step forward for road safety.  But in addition to illicit drugs, the new regulations cover certain prescription medicines and here I have a few concerns. The situation with illicit drugs is straightforward in that they are illegal for drivers or anyone else. The situation with drink-driving is a little different because alcohol is not illegal in the UK but a responsible driver nevertheless has the choice not to drink before getting into the car. Prescription drugs are a bit of a grey area however, because they can potentially impair driving ability but they are a necessary medication for the driver.

I’ll take one drug from the list of those now being regulated in respect to driving: morphine (for chronic pain). Morphine can certainly cause drowsiness and the small-print in the information leaflet advises the patient not drive if they feel impaired. More patients might be taking morphine than they realise however, because the presence of morphine in the bloodstream results from taking another medication, codeine.  Many patients, when asked if they have taken morphine might truthfully reply that they have not, but nevertheless test positive because they have been prescribed codeine. I have a prescription for codeine to treat osteoarthritic chronic pain and I can state categorically, that I have had no warnings or information on this whatsoever.

Sufferers of chronic pain who take morphine (in the form of codeine) build up a resistance to its effects. A standard prescription dose of codeine is around 30-60 mg for chronic pain. Someone taking this medication on a regular basis would get pain relief without feeling any major adverse effects. If someone who was not on regular codeine took this dose then it would likely send them into a tail-spin. The maximum blood concentration of morphine after taking 30 mg codeine is typically around 200 ug per litre (a ug = a millionth of a gram), whereas the legal limit is now set at just 80 ug per L.  Over-the-counter codeine comes in typically 3-4 mg tablets and two of those will typically result in blood maximum concentration of around 40 ug/L, which although lower than the limit is starting to approach it. Codeine is also present in some cough medication. Moreover, someone not taking codeine regularly will certainly feel the effects of a 40 ug per L blood concentration and in some cases may not be fit to drive. It is therefore hard to legislate the genuine effects on driving prescription codeine might have, based purely on a blood concentration.

There is another side to this same coin, in that someone who is on a prescription for codeine could avoid prosecution based on a medical defence. In theory if they give a positive road-side test for morphine and they can provide evidence to the officer that they are on prescription medication, then no action should follow. In practice this is going to depend on what they have been stopped for and the judgement of the police officer. A car is a ton and a half of weaponry in the wrong hands, and we should all take the privilege of driving responsibly.  On the other hand, care has to be taken not to criminalise responsible drivers because they have to take prescription medication - as I say, this is a bit of a grey area.

I will end on what might be an urban myth, but then again might not. Poppy seeds contain opiates and substances such as morphine can be detected in the bloodstream after consumption. Could a driver be prosecuted therefore, for eating a bagel dusted in poppy seeds?  Studies have been conducted over a number of years and the answer is - probably not, but it couldn’t be ruled out. Poppy seeds contain quite high concentrations of opiates, in some cases up to 200 mg/kg (a mg is a thousandth of a gram). Eating a single bagel even liberally dusted with high opiate-containing poppy seeds is unlikely to result in blood morphine concentrations exceeding 80 ug/mL. One test in Germany resulting in blood opiate concentrations reaching 10 ug per L and so it’s not impossible that a poppy seed or bagel addict might fall foul of the law but it’s pretty unlikely and I would not advise trying it out as a legal defence.