The globalisation brought about by the internet means that recreational drug use is now a worldwide issue. And for legislators, drug taking is a rapidly moving target. Over past decades, we have seen changes in how drugs are being used, with new combinations of drugs being used together. But why does this happen?

It has long been known that street samples of heroin often contain a mixture of drugs. In some cases different drugs are added to counter the effects of the drug which has been taken.

Heroin is manufactured from the morphine contained in the latex of the field poppy, Papaver somniferum. The morphine is extracted, reacted with acetic anhydride and turned into diamorphine – the desired drug. This is then mixed with an acid, rendering the drug water soluble, heated and then injected.

Street samples of heroin are often mixed with benzodiazepines (commonly temazepam or diazepam) and barbiturates (often phenobarbitone). Benzodiazepines, anti-anxiety drugs, are added to reduce the stress of taking the heroin. When the body clears the heroin from the system the process can induce a pseudo-epileptic fit. Some barbiturates, particularly phenobarbitone, have been used to control epilepsy and they are added to reduce the risk of fitting after taking heroin.

New trends

Sometimes taking drugs or drug mixtures can be part of a trend. What causes these trends is not always understood.

Despite an overall decline in the use of recreational drugs an increase has been reported in cocaine use among younger people, while another recent reported trend is the growth in the use of so-called Monkey Dust in the UK. This is a synthetic stimulant related to the cathinones, which has similar effects to cocaine and amphetamines.


Sometimes a trend is caused because a drug or drug mixture is sought which has a similar effect to drugs which have become difficult to obtain or which have become too expensive. For example, in 2009 the number of seizures of cathinones increased in Cambridge, UK, when the world supply of sassafras oil, a precursor of MDMA, dried up. When the supply of the precursor was reestablished, MDMA use returned and the use of cathinones fell.

Seizures of Cathinones and Ecstasy recorded in Cambridge, UK, between 2003 and 2013. Source: Alexandra Turner, 2015

In Russia, Krokodil – a homemade version of the synthetic opioid desomorphine – provides a cheap alternative to heroin. It is readily manufactured from codeine but its use can result in terrible physical injuries as well as the harms associated with drug abuse itself.


A legislative change can sometimes cause a change in the use of drug mixtures. For example, mixtures of piperazines, compounds which cause similar effects to ecstasy, emerged on the drug market as a legal alternative to methamphetamine in New Zealand. As a consequence, mixtures of these drugs emerged as different effects were realised. Some mixtures are still commonly encountered, including benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (3-TFMPP). Other drugs in this family have been reported to be mixed with cocaine, ephedrine and caffeine.

Such changes, in response to legislative control, have been observed in older, “more established” drugs as well as the novel psychoactive substances. In addition, “cheaper” drug mixtures may be developed for socioeconomic reasons. For example, in South Africa there has been an the emergence of a drug named Nyaope. We have found this to contain a mixture of low-grade heroin, cannabis and the antiretrovirals: efavirenz and nevirapine.

The effects of cannabis and heroin are well known. What is less well known is that some antiretrovirals, including those found in this drug, are hallucinogenic and cause dissociative effects. As a consequence of this, and the low cost (30 Rand or £1.60 per dose), it is finding widespread use in the poor communities where its use is rife. The problem with this drug is that it is also highly addictive and causes extra problems as users resort to crime to finance their habit. In addition, it poses particular challenges to the forensic science community as the mixture of drugs found in Nyaope have chemical properties which make them problematic to analyse and profile.


Some people take drug mixtures because they are looking for a new, or more intense high. The National Forensic Laboratory System in the US indicated that in Pennsylvania, for example, there was a trend to mix heroin with fentanyl which declined from 2006 to 2010 (when no such mixtures were observed). This decline then reversed and there was a steady resurgence in this drug mixture between 2011 and 2016, with 65% of heroin cases reported to contain fentanyl in 2016. When the percentage of fentanyl decreased there was an increase in other drugs – benzodiazepines, cocaine, and “other non controlled drugs”.

Composition of heroin/fentanyl mixtures reported in Pennsylvania 2006-2016. Source: Data drawn from the DEA Bulletin, February 2018

This is a worrying increase. Fentanyl, which is 50-100 times more potent than morphine and up to 50 times more powerful than diamorphine (both found in heroin), is particularly dangerous because it does not need to be ingested – it is readily absorbed through the skin or through inhalation of the drug powder. Not only does this present a risk to anyone using the drug but also anyone attending a victim as a first responder or, indeed, forensic scientists analysing the drug.

The drug is mixed with heroin, or cocaine, leading to potent cocktails of drugs which are dangerous in the extreme. One mixture, Grey Death, contains fentanyl, carfentanil (a synthetic opioid used by vets to treat very large animals), heroin and a synthetic opiate, U-47700. U-47700 is itself seven times more potent than morphine and carfentanil is a staggering 10,000 times more potent than morphine. Two milligrams (a teaspoon of sugar weighs 2,500 times this much) of carfentanil can be fatal. A similar mixture, Purple Heroin, is a combination of heroin, morphine, fentanyl and carfentanil. Very little drug is required to have an effect and even small amounts can cause seizure, arrhythmia, breathing difficulties and death.

Warning label

So what are the consequences of taking drug mixtures? The effect of any drug will depend upon such factors as the age, gender, health status, drug taking history and mood of the user. No two people will be affected in the same way by a drug or drug mixture. Drugs do not simply counteract each other, and alcohol often makes the effect or problem greater – in addition to rendering the user liable to forget how much and which drugs they have taken. While taking drug mixtures may be driven by curiosity or other reasons, given what we do know, the safest bet perhaps is to avoid them altogether.

Michael Cole, Professor of Forensic Science, Anglia Ruskin University.

This article first appeared on The Conversation.