Fentanyl: general

Fentanyl is a synthetic opioid [1] and a µ-opioid receptor agonist [1], first synthesised by Janssen Pharmaceutical [2] and approved for medical use in the US in 1968 [3][4]. It's used in medicine for severe pain, general anaesthesia, breakthrough cancer pain, and as a sedative for intubated patients [3][4], in forms including injectable solutions, transdermal patches, transmucosal lozenges, and buccal tablets [2].

The one fact that matters most: fentanyl is roughly 50 to 100 times more potent than morphine [4][5], with some sources putting it at least 80 times [2] or around 100 times [1].

Pills that are given to you or bought from a friend may look like a safer drug, but might contain lethal doses of nonmedical opioids, including fentanyl [6]. As with opioids generally, these drugs bind to receptors in the brain that normally send signals to keep breathing; overriding those signals causes breathing to slow and eventually stop [6].

As with opioid overdose generally, a fentanyl overdose is treatable rather than something to wait out: it's reversible with naloxone and basic life support if given in time [7]. Naloxone has virtually no effect in people who haven't taken opioids [7]. As with opioids generally, naloxone stays in the body for a shorter time than many opioids [8], and heroin and other opioids can stay in the body for much longer than naloxone [8]. That's why someone who's been revived needs to keep being watched, not left alone the moment they come round.

Never use alone. If you use with others, agree who stays alert and know how to get naloxone before you need it.

References

1. Fentanyl — Drug Enforcement Administration, Diversion Control Division
2. Fentanyl drug profile — European Union Drugs Agency (EUDA)
3. fentanyl | Ligand page | IUPHAR/BPS Guide to PHARMACOLOGY — IUPHAR/BPS Guide to Pharmacology
4. Fentanyl - StatPearls — NCBI Bookshelf
5. Fentanyl — Encyclopedia Britannica
6. Opioid Overdose: Signs, Symptoms & Treatment — Cleveland Clinic
7. Opioid overdose — World Health Organization
8. Opioid medicines - side effects, withdrawal symptoms, dependency — Australian Government Department of Health and Aged Care