Most recently came warnings about fentanyl-type drugs . Such bulletins can risk losing impact , but if the evidence from North America and elsewhere is anything to go by , fentanyl and its derivatives have the potential to become a huge problem and cause significant loss of life .

Although fentanyl-type drugs have featured sporadically in the UK drug scene for a while , concern about them has increased markedly in the past few months , leading to official warnings from the National Crime Agency ( NCA ) and Public Health England ( PHE ). So , it ’ s time ( and some would argue , long overdue ) to get up to speed with the fentanyls .

Fentanyls are opioids , with fentanyl ( Duragesic ) used for severe pain . It has numerous analogues and derivatives , with new ones emerging – Wikipedia lists 42 and this may be an underestimate . Several of the fentanyls have legitimate medical use and so are better understood in terms of potency , doses , and metabolites , but others have been developed to sidestep legislation or restriction on precursors . Less is known about these newer compounds .

The potency and half-life of different fentanyls varies massively . To illustrate relative potency , fentanyls are compared to morphine – but this is a crude indicator , especially when the composition and purity of street-sourced fentanyls is unclear .

To further complicate the issue , some analogues have more than one isomer , which in turn vary in potency . So 3-methylfentanyl ranges in potency , from 300 times the potency of morphine to 6,000 times stronger , depending on which isomer is present .

Given such a wide range of products and potencies , the risk of overdose cannot be understated . There is every chance of misidentification and misselling throughout the supply chain , from producers inadvertently supplying the wrong analogue or isomer through to suppliers mis-identifying their product .

To reduce the potency to usable levels , fentanyls need to be bulked out with a non-psychoactive filler agent , such as mannitol . This demands correct identification of the drug , careful calculation of the amount of filler to be added , and thorough mixing of drug and filler .

Such mixing is at best prone to errors . When fentanyl is mixed with more granular substances , such as brown heroin , it is impossible to achieve a thorough mix , and so the risk of separation and ‘ hotspots ’ is greater still .

Fentanyl is rated as approximately 100 times * the potency of morphine – so 1g of fentanyl is equivalent to 100g of morphine .

Some analogues are weaker : acetylfentanyl is around 15 times the potency of morphine . Others are far stronger : 4-fluorofentanyl is reported to be twice the strength of fentanyl – some 200 times the strength of morphine .

Carfentanil , legitimately used to tranquillise large mammals , is reportedly around 10,000 times the potency of morphine ( 100 times stronger than fentanyl ). So , in theory , 1g of carfentanil is the equivalent of 10kg morphine .

* This dose equivalence is a very crude way of indicating relative potency . Variables such as speed of onset , duration of effect , level of analgesia versus level of sedation , and therapeutic index cannot be summarised by a simple drug A is x times stronger than drug B .

SOURCES AND SUPPLY Synthesised in China and elsewhere , fentanyls have become increasingly available on the dark web . Products reputedly on sale included fentanyl , furanylfentanyl , carfentanil and other analogues .

Given their very high potency , they are an appealing option for international smuggling . They offer a low bulk / high potency alternative to heroin and are available via labs online , rather than engaging with heroin suppliers .

Fentanyls have become a very significant factor in drug deaths in North America and the major cause of opiate deaths in British Columbia , with the number almost doubling between 2015 and 2016 . Closer to home they have been an issue in the EU , but it has primarily been Baltic countries , especially Estonia , which have seen the biggest problems .

There may also be some European production . In April , West Yorkshire Police raided a ‘ drugs lab ’ where fentanyl was involved , although is not clear from the reporting if the ‘ lab ’ was synthesising fentanyl , or compounding imported fentanyls with heroin for onward sale .

THE UK MARKET Medically diverted fentanyl is abusable , but the combination of limited prescribing and transdermal preparations has meant it has not been a massive issue in the UK to date . Fentanyl analogues have been around here for a while , cropping up sporadically in drugs analysed ( for example ) by the drug identification service WEDINOS , but difficulties in detecting newer fentanyls make it hard to gauge their presence . It may be that they have been a factor in opiate drug deaths for longer than thought , and reviews of post-mortem samples are being conducted to see if this is the case . Routine drug testing and screening won ’ t show up fentanyls and even fentanyl-specific tests won ’ t detect all analogues .

While fentanyl is most likely to appear as a cut in heroin , it is also sold online as a white powder and has been offered in liquid and blotter forms . It can be smoked , snorted , injected , or taken rectally , and while all routes are risky , smoking carries the lowest risk of fatal overdose . At street level in the UK , it is most likely

8 | drinkanddrugsnews | June 2017 www . drinkanddrugsnews . com