The world’s stupidest drugs law, the Psychoactive Drugs Act, has come into effect in the UK last week and it claims to prohibit the creation and supply of all psychoactive substances not already covered by pre-existing drugs laws.

Apart from taking us further down the futile road of prohibition it is premised on something that’s scientifically impossible – testing if a seized drug is psychoactive from looking at its chemical structure.

The government claimed that they had ‘solved’ this problem and they’ve just released their forensic strategy document which, unsurprisingly, doesn’t actually solve it.

What it does do, however, is worthy of attention as it likely raises a whole new set of problems.

We learn from the forensic strategy that the test for ‘psychoactivity’ is to submit mystery substances to receptor binding assays – a lab test where the substance is added to cells ‘in a dish’ which have receptors for certain neurotransmitters to see if substances bind to and activate the receptors.

Your brain has many, many different forms of receptors, so the government has defined a list that will supposedly indicate whether a substance is ‘psychoactive’ based on whether a substance binds to and activates one of the following:

CB 1 (targeted by cannabis and synthetic cannabinoid type drugs)

(targeted by cannabis and synthetic cannabinoid type drugs) GABA A (targeted by benzodiazepine type drugs)

(targeted by benzodiazepine type drugs) 5HT2 A (targeted by hallucinogenic type drugs – these can be from a number of different types of drugs)

(targeted by hallucinogenic type drugs – these can be from a number of different types of drugs) NMDA (targeted by dissociative/hallucinogenic drugs e.g. ketamine)

µ-opioid (targeted by opioid drugs e.g. heroin) and

monoamine transporters (targeted by stimulant drugs e.g. MDMA, cocaine).

These are indeed receptors that facilitate some of the major recreational drug groups but this is not an adequate definition of ‘psychoactivity’ not least because there are several psychoactive substances that don’t affect these receptors.

Most notable is long-running ‘legal high’ salvia divinorum which is wildly hallucinogenic but has its effect through the non-listed κ-opioid receptor.

So produce a lab-based tweak on the salvinorin A molecule, the ‘active ingredient’ in Salvia, and you have something that won’t be picked up by government tests.

The main problem though, is likely to be that these tests will be over-inclusive. Lots of substances will activate these receptors without having a psychoactive effect.

For example, epinastine is a drug in eye drops that strongly activates the 5HT2 A in the lab but which doesn’t have a psychoactive effect because it doesn’t cross the blood-brain barrier.

Acamprosate is a drug used to treat alcoholism, not typically considered to be psychoactive, and yet activates GABA A receptors.

There are many more examples and they’re not hard to track down – mainly because we now have several open databases of drugs and receptor interactions so you can easily find psychoactive drugs that will screen negative or non psychoactive ones that will be falsely detected as mind-altering.

In practice, what this means is that lots of substances – chemicals from the home, the workshop, the lab, and the pharmacy – may screen for ‘psychoactivity’ but not be psychoactive. False positives, in other words.

But this approach also shows that the Psychoactive Drugs Act fails at solving the problem it is meant to overcome: underground labs producing new substances faster than they can be added to a list of banned drugs.

The Act just complements a fixed list of banned drugs with a fixed list of banned drug effects – making it just another target for grey market labs to innovate around.

What’s also interesting from the list is what drug effects are not proscribed – and we can probably expect underground innovation in pure D 2 dopamine agonists that don’t affect monoamine transporters for uppers, and antihistamines as downers, among others. Although to be honest, most will likely just keep on using the same substances.

But considering that the biggest take home from ‘legal highs’ is that they were much worse for your health than ‘illegal highs’ – perhaps the best public health result we can hope for is that the Psychoactive Drugs Act pushes recreational drug users back to using the less harmful classics – speed, MDMA, weed and so on.

And when that’s the best you can hope for, you really know that your drug laws are in a dismal state.