Drugs, Medicines and Driving

Pharmacology Expert Witness
Mephedrone and Driving

Mephedrone and Driving

A 37 year-old mother of three was stopped by police one morning for erratic driving. She was found, subsequent to her arrest, to her obvious surprised horror to have mephedrone in her blood.

Expert Witness Pharmacology


Mephedrone - 4-methylmethcathinone (4-MMC), or 4-methylephedrone is a synthetic substance based on the (cathinone) compounds that exist in the Khat plant of East Africa.

Mephedrone is a powerful stimulant and is part of the cathinone family, a group of drugs that are closely related to the amphetamines – including amphetamine itself (often called ‘speed’) and methamphetamine.

Mephedrone can be found as a fine white, off-white or a yellowish powder. It can also be found in capsules or tablets.

All cathinone derivatives, including mephedrone, methylone, methedrone and MDPV are Class B drugs under the Misuse of Drugs Act 1971. It is illegal to be in possession of the drugs and to sell them. The substances are controlled under generic legislation i.e. all cathinone derivatives are covered by the Misuse of Drugs Act.


The initial investigation identified the following:

  • She had attended a party the previous night, but had stuck to soft drinks throughout; mainly Coca Cola.
  • Medically, she was on rizatriptan (an anti-migraine drug) and propranolol (a beta blocker, mainly used for controlling blood pressure, although also used extensively for anxiety by doctors wishing to avoid using benzodiazepines which are liable to dependency).

Of relevance and importance is the documented interaction between the two drugs. Propranolol is known to increase the blood level of rizatriptan to the extent that the manufacturer of rizatriptan recommends that the dose is HALVED when in conjunction with propranolol, and that the combination is avoided within at least 2 hours.

The clinical picture suggested in all the evidence was consistent with such a drug interaction; a specific toxicity syndrome consistent with the interaction. The effects include drowsiness, dry mouth, thirst, headache, decreased alertness, insomnia, tremor, ataxia, nervousness, vertigo, confusion, sweating, itching and blurred vision.

The very fact that a blood level of mephedrone was found therefore suggested to me that a further drug interaction may have occurred; centrally acting 5-hydroxytryptamine (a central neurotransmitter) may have been potentiated by at least 3 interacting agents. Mephedrone is a synthetic CNS stimulant, similar chemically to the amphetamines.

Some mephedrone preparations have little or no taste at all, whereas other specimens have a fishy or ‘burning electric’ type of smell and taste. However, any taste is easily masked with Coca Cola, which drink has previously been used to dope an unsuspecting athlete with cocaine in one of my previous cases.

Speed of effect onset after an oral dose is usually cited as being between 15 – 45 minutes.

I have encountered in other cases the sharing of mephedrone in party drinks. Therefore, the story provided was both plausible and consistent with the known interaction.

I considered that the subject had stayed up all night, enabled easily to do this by consumption of mephedrone perhaps gradually and consistently, as she was drinking soft drinks during the whole evening until the early hours. Anxiety being a known side effect might then have become manifest.

The following morning, a headache – entirely likely from the ingestion of mephedrone – might then have been addressed by a rizatriptan tablet, taken before driving the children somewhere, leading to results observed.

It is easily possible that the effects of this combination would not have been readily apparent to the subject. Even worse: Within half-hour before driving the client consumed some of the left-over flat Coke. It is therefore plausible that the combined effects resulted in “total destruction of voluntary control” because she did not realise that she was intoxicated, especially as propranolol and rizatriptan, two additionally interacting drugs, were also involved.


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