Fentanyl addiction

Research shows that fentanyl leads to addiction in one in four people who use it; one of the highest fractions of all addictive drugs.

Fentanyl works by binding to specific receptors in the brain and nervous system that regulate pain to block pain signals. At the same time, it activates the brain’s reward system, releasing dopamine and producing a sense of relief and well-being.

Studies in mice have identified two separate brain circuits driving this:

•  One responds to the pleasure the drug produces 
• The other drives continued use to avoid the distress of stopping

With extended use, the brain adjusts to the constant presence of the drug. This means that it produces less of its own natural pain relief and reward chemistry, because fentanyl is doing that work instead. The result is tolerance, where the same dose produces less effect than it did before. 

As tolerance builds, the return of pain can feel like the original condition worsening rather than the brain adapting to the drug.

Tolerance then can lead to increased fentanyl use. This in turn leads to physical dependence, where the body needs fentanyl present to function normally, and stopping produces withdrawal. Dependence can develop in anyone taking fentanyl for an extended period, including people who’ve never taken more than they were prescribed.

Dependence is not the same as addiction, though the two are often confused. Addiction means compulsive use that continues despite harm. It involves the brain’s reward and motivation systems rather than just its physical adjustment to the drug. A person can be physically dependent without being addicted.

For some people, the escalation stops at dependence. For others, the drug starts to occupy more of their thinking than the pain does, and use continues even when it is causing visible harm. That is the point at which dependence has become an addiction to fentanyl.

Recognising problematic fentanyl use is not always straightforward, particularly when the drug was prescribed. The ICD-11 sets out diagnostic criteria for opioid dependence – including fentanyl addiction – and other opioid-related disorders, but you don’t need a formal diagnosis to recognise when someone may need help.

What you might notice in yourself:

• Needing more fentanyl than prescribed to get the same effect
• Feeling anxious or unwell when a dose is delayed or missed
• Finding it hard to reduce or stop despite wanting to
• Using fentanyl to manage mood or anxiety as well as pain
• Spending more time focused on supply, timing of doses, or running out

What someone close to you might notice:

• Changes in mood or energy that coincide with fentanyl use or withdrawal
• Giving up normal activities
• Neglecting important relationships
• Increasing secrecy around medication
• Visible distress when fentanyl supply runs out

Yes. Fentanyl use disorder is a chronic medical condition, and with the right support, people do recover from fentanyl addiction.

In an independent analysis of Castle Craig patient outcomes, 91.8% of patients showed measurable improvement one year after treatment. 73.4% were abstinent at one year. These figures come from research by Christo Research Systems of a mixed cohort of patients admitted for opioid and substance use presentations.

How to treat fentanyl addiction depends on the individual, but treatment usually involves medically supervised detox, residential therapy, and support after discharge.