People found driving with a high level of certain anti-anxiety or epilepsy prescription drugs in their bloodstream could fall foul of new drug driving laws.

Lorazepam, a drug for treating epilepsy, diazepam and oxazepam, both used for treating anxiety are some of the prescription drugs that will fall under the new law, when introduced from 2 March 2015.

“The specified limit allows for normal recommended doses most patient would be prescribed if taking their medication properly,” said the Royal Pharmaceutical Society.

A “medical defence” is now allowed if the patient is taking medication as instructed by a healthcare professional, provided their driving has not been impaired. However, should someone be found to have taken these drugs without a prescription, they could face prosecution.

The full list of prescription drugs are with driving limits are:

  • clonazepam (50 µg/L)
  • diazepam (550 µg/L)
  • flunitrazepam (300 µg/L)
  • lorazepam  (100 µg/L)
  • methadone 500 µg/L
  • morphine or opiate and opioid-based drugs (80 µg/L)
  • oxazepam (300 µg/L)
  • temazepam (1000 µg/L)

The laws will include eight illegal drugs such as cannabis, cocaine, LSD, MDMA and heroin at levels of no more than 50µg/L.

The law will apply to England and Wales from 2 March 2015. Scotland will introduce the rules at a later, unconfirmed, date.

Penalties for drug driving will include a minimum of a one year driving ban, up to a year in prison and a fine up to £5,000.