Fentanyl

Fentanyl is a synthetic opioid analgesic first synthesised by Dr. Paul Janssen in 1960. The drug was developed as a potent analgesic, approximately 50 to 100 times stronger than morphine.^1,2 Initially used in medical environments for pain relief, the substance has also been found in illicit markets, where it’s often mixed with other narcotics, increasing its risk profile.³

After its discovery in the 1960s, fentanyl received approval for medical applications and started being sold under various brand names such as Sublimaze.⁴ Over subsequent years, different formulations like patches, lozenges, and injectables were developed for various medical applications, including chronic pain management and surgical anaesthesia.⁵ The drug also emerged in illicit forms in the late 20th and early 21st centuries, leading to a significant rise in overdose fatalities.⁸

Medically, fentanyl is utilised for its strong analgesic effects. It binds to opioid receptors in the brain, thereby dulling the pain sensation.⁹ However, fentanyl comes with significant side effects, including respiratory depression, nausea, and potential unconsciousness.⁶ When used illicitly, its potency is often underestimated, resulting in a high likelihood of overdose and mortality.⁷ The drug is also highly addictive, causing physical dependence and withdrawal symptoms when misused.¹⁰

Appearance

Fentanyl appears in various forms depending on its intended use. It is often presented as a clear, odourless injectable liquid in medical settings. Skin patches used for pain management are generally beige. Illicit forms of fentanyl are typically found as a white powder, although it can also take the form of tablets or blotter paper.^1,3,6

Tastе

Fentanyl generally lacks a strong taste, making it easy to mix with other substances without detection. In medical settings, fentanyl lozenges may come in various flavours to make them easier to consume. However, the absence of a strong or distinctive taste in most formulations is particularly concerning, as it contributes to the risk of accidental overdose when the substance is unknowingly mixed with other drugs. ^3,5

Smell

Fentanyl is generally odourless, which adds to its danger as it can be easily mixed with other substances without drawing attention. This lack of smell holds true for its medical forms, such as injectable liquids and patches, and illicit forms such as powders and tablets. ^1,3

It’s important to note that self-reported dosages of fentanyl from non-medical sources are highly unreliable and risky due to the drug’s extreme potency and the variable purity of illicit forms. Some people may report using “a small grain” or “a pinch,” but these measures are imprecise and potentially lethal. In medical settings, fentanyl dosages are carefully calculated and administered by healthcare professionals, often ranging from 25 to 100 micrograms intravenously, depending on the individual’s medical condition and other factors.^3,5

• Minimum to Feel Something (mg): The threshold to feel the effects of fentanyl is exceedingly low due to its extreme potency. For many people, as little as 0.5 to 1 microgram per kilogram of body weight can produce noticeable effects. This means for an average adult weighing 70 kg, around 35 to 70 micrograms could produce noticeable effects. It’s critical to note that these figures are not an endorsement for recreational use; even at these low levels, fentanyl poses a high risk of respiratory depression and overdose.^3,5
• Low Dose: In a clinical context, a low dose of fentanyl is generally in the range of 25 to 50 micrograms for intravenous administration in adults. These low doses are often used for less invasive procedures or as part of a balanced anaesthesia technique. Given fentanyl’s high potency, even these “low” doses need to be precisely measured and administered under strict medical supervision to prevent adverse effects such as respiratory depression.^5,6
• Common Dose: In a medical setting, the common dose of fentanyl varies widely depending on factors such as the patient’s age, medical condition, and previous exposure to opioids. Due to its potency, the drug is often administered in micrograms rather than milligrams. For example, an initial intravenous dose may range from 50 to 100 micrograms in adult patients undergoing surgery. It’s crucial to understand that these dosages are tightly controlled and monitored by healthcare providers to mitigate the risks of overdose and other adverse effects. ^5,6
• High dose: The term “high dose” is highly context-dependent when it comes to fentanyl, owing to its extreme potency. Even a small amount can be lethal, especially for individuals who are not opioid-tolerant. In a medical context, high dosing would be rigorously controlled and monitored. Still, in illicit use, a high dose could be as little as 2 milligrams, depending on purity, potentially leading to immediate respiratory depression and death. ^1,5

What May Happen When Exceeding High Dose

Exceeding a high dose of fentanyl can lead to severe medical complications and is often fatal. The most immediate risk is respiratory depression, where breathing becomes dangerously shallow or stops altogether. This can quickly lead to hypoxia, a condition where not enough oxygen reaches the body’s tissues, resulting in unconsciousness, brain damage, and death. Other symptoms may include extreme drowsiness, confusion, and constricted pupils. Immediate medical intervention is critical in cases of suspected overdose.^1,6

The feeling experienced after taking fentanyl varies depending on the context. In a medical setting, patients may experience significant pain relief and potential feelings of euphoria. For illicit use, users often report intense euphoria, relaxation, and sedation. However, it’s crucial to note that these effects come with significant risks of overdose and death.^2,10

The onset time for fentanyl’s effects can vary depending on the route of administration. When administered intravenously in a medical setting, fentanyl takes effect almost immediately, generally within 1 to 2 minutes. When used intramuscularly, the onset is slightly slower, typically taking up to 5 minutes to kick in. Transdermal patches have an even more gradual onset, taking hours to start providing relief. In the case of illicit use, onset can be rapid and unpredictable, especially if the drug is mixed with other substances.^3,5

The duration of fentanyl’s effects can vary depending on the route of administration. When used medically, its effects are often short-lived, lasting around 30 to 90 minutes. However, some formulations, like patches, can have prolonged effects, lasting up to 72 hours. It’s crucial to understand that even when the felt effects wear off, the drug may still be in the system, increasing the risk of overdose if additional opioids are taken. ^5,6

The risks associated with fentanyl use are substantial and can be life-threatening. Due to its high potency, the margin for error in dosing is very narrow, making overdose a significant concern. Overdose can result in respiratory depression, unconsciousness, and death. The drug’s potency also makes it susceptible to misuse and illicit production, where it is often mixed with other substances, significantly increasing the risks.^1,7

Fentanyl is highly addictive due to its potent opioid effects. The drug triggers the release of dopamine, a neurotransmitter associated with pleasure, reward, and reinforcement, which contributes to its high potential for abuse. Dependency can develop rapidly, even when used as prescribed by a healthcare provider. Moreover, once a dependency is established, withdrawal can be challenging and may require medical intervention for successful treatment.^3,6

In the United Kingdom, fentanyl is classified as a Class A controlled substance under the Misuse of Drugs Act 1971. This means it is illegal to produce, possess, or supply the drug without a proper prescription or licence. Penalties for violating these laws can be severe, including imprisonment for up to life for supply and production and up to seven years for possession.^12,6

Mixing fentanyl with other drugs can be extremely dangerous and is strongly discouraged. The risk of fatal overdose significantly increases when fentanyl is combined with other opioids, alcohol, or sedative drugs like benzodiazepines. Such combinations can lead to respiratory depression, a condition where breathing becomes dangerously slow or even stops, ultimately resulting in death. ^1,3

1. CDC. Opioids Basics. Available at: https://www.cdc.gov/opioids/basics/fentanyl.html
2. DEA. Fentanyl Factsheet: https://www.dea.gov/factsheets/fentanyl
3. NIDA. Fentanyl Drug Facts. Available at: https://nida.nih.gov/publications/drugfacts/fentanyl
4. UMassMed. What is Fentanyl?: https://www.umassmed.edu/news/news-archives/2022/05/what-is-fentanyl-and-why-is-it-behind-the-deadly-surge-in-us-drug-overdoses/
5. HealthDirect. Fentanyl. Available at: https://www.healthdirect.gov.au/fentanyl
6. NHS. Fentanyl. Available at: https://www.nhs.uk/medicines/fentanyl/
7. Canada Health. Fentanyl. Available at: https://www.canada.ca/en/health-canada/services/substance-use/controlled-illegal-drugs/fentanyl.html
8. CFR. Fentanyl and US Opioid Epidemic: https://www.cfr.org/backgrounder/fentanyl-and-us-opioid-epidemic
9. Drugbank. Fentanyl: https://go.drugbank.com/drugs/DB00813
10. ADF. Fentanyl Drug Facts: https://adf.org.au/drug-facts/fentanyl/
11. HHS Texas. Fentanyl: One Pill Can Kill: https://www.hhs.texas.gov/services/mental-health-substance-use/mental-health-substance-use-resources/fentanyl-one-pill-kills
12. UK Government. Misuse of Drugs Act 1971. Available at: https://www.legislation.gov.uk/ukpga/1971/38/contents