Synthetic Opioids: Insights on Recent Trends and a Look at the Future

25 avril 2025

Article checked/verified by Drug Science,

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There are two terms primarily used to describe the drugs in question. The term opiate refers to natural alkaloids which bind to the opioid receptors in the brain. Opiates are derived from opium. The term opioid refers to all natural or synthetic compounds which bind to the opioid receptors. This blog focusses on relatively recently developed synthetic opioids.

Are synthetic opioids more dangerous than opiates?

Although the term synthetic opioid is typically used (especially in the news!) to refer to extremely potent opioids, this isn’t always the case.

There are examples of synthetic opioids with weaker affinity for the opioid receptors than their natural counterparts (tramadol being a good example of this). These opioids are often overlooked, and it should be noted that they are not necessarily safer just because they are weaker.

However, there are also examples of synthetic opioids which are much, much more potent than natural opiates like heroin. Most fentanyl analogues and nitazenes fall into this category of highly potent opioids.

Other risks from synthetic opioids stem from their lack of research. For example, the novel psychoactive substance U-47700 is known amongst people who use opioids for being a highly caustic substance. This can lead to increased damage to the veins and skin, as well as the nose, depending on the route of administration. U-47700 is also significantly more potent than morphine, and could result in overdose if mis-sold.

Fentanyl

Fentanyl is probably the most well known synthetic opioid ever created. It is very potent, with a potentially lethal dose of just 2mg in opioid naive users, and is often sold in place of traditional opioids.

Fentanyl is used medically in the UK to treat severe pain, especially post-surgery. It was first developed in the late 1950s and first used medically in Europe in 1963, though some countries were slower to begin using the drug.

This timeline, then, begs the question of why we saw its illicit use skyrocket in 2013, exactly 50 years after it was introduced into medical care.

The rise of fentanyl in the UK cannot be examined meaningfully without considering the role that the US played in the crisis. America was among the earliest countries to experience the fentanyl crisis, and among the hardest hit. For various reasons, the American population had record high levels of opioid users, many of whom were severely mismanaged patients who had been cut off from their supply. This lead to these people seeking out illicit opioids, decreasing their availability on the street and increasing their prices. This, combined with decreased production in heroin producing areas, lead to a search for an opioid to replace heroin. Fentanyl was the obvious choice. Its potency means that it can be easily smuggled between countries and small amounts could be added to other drugs to create the impression of a more pure drug.

In the UK fentanyl came slightly later, and did not lead to as many deaths as it did in America. In 2021, the number of deaths from fentanyl per 100,000 people was just 1% of the American figure. There are many potential factors that helped keep the UK largely free of fentanyl.

However, the potency of fentanyl can make it very risky. The risk of hotspots and accidental overdose increase massively when comparing fentanyl with traditional opioids like heroin and morphine. It is vital that you test your drugs with our opioid testing kits, and remain vigilant if you believe you may have been sold fentanyl.

There has also been a rise in opioids being contaminated with xylazine, a veterinary anaesthetic. This combination is often referred to as ‘tranq dope’ and can create the impression that opioids are more pure by increasing the effects of the fentanyl. The combination of fentanyl and xylazine can increase the harms of using either drug alone. Xylazine has been linked to skin lesions, severe withdrawal symptoms and even increased risk of death from overdose. Xylazine has recently been detected in the UK drug market, and notably has been found in the absence of opioids - meaning that a wider population of people who use drugs may be affected.

Nitazenes

Nitazenes are a group of synthetic opioids which were first developed in the 1950s but were never approved for medical use. There are a number of nitazenes in the illicit market which range in strength from being similar to heroin to some analogues with similar strength to fentanyl.

Nitazenes have been introduced into the illicit drug supply in the UK relatively recently. When they were first detected in the illicit drug supply they were not covered by the Misuse of Drugs Act 1971, making them less risky to be found to be importing. Nitazenes are also very cheap to produce and, like fentanyl, the potency of some nitazenes makes it possible to stretch a smaller supply further. Many nitazenes have since been added to the MDA71 as class A drugs.

How to avoid nitazenes

Due to the novel nature of nitazenes, the number of analogues in the illicit market and their potency it is very hard to tell if your drugs contain nitazenes. It is always important to test your drugs with our opioid drug testing kit, but ideally professional drug testing services like WEDINOS would be used where nitazenes are suspected.

Synthetic Opioids: Conclusions

Synthetic opioids are a growing problem in the UK and elsewhere. Many synthetic opioids are under researched and their long term risks are unknown, as well as often being much stronger than their traditional counterparts.

You can reduce your risk by ensuring that you test your drugs, starting with a much lower dose than usual if you are using a new batch, and ensuring that you and anyone around you has naloxone on hand in case of overdose. Naloxone can be accessed through your local pharmacy by anyone who uses drugs or is often in contact with someone who uses drugs.