Fentanyl
A synthetic, highly lipid-soluble mu-opioid agonist used in anesthesia and, as a skin patch, for severe long-term pain in opioid-tolerant patients.
Drug card
- Class
- Opioid
- How it works
- Activating mu-opioid receptors in the brain and spinal cord to dull pain
- Used for
- Pain relief during and after surgery
- Adjunct to general and regional anesthesia
- Cancer pain
- Long-term severe pain in opioid-tolerant patients
- Known for
- Slowed breathing and apnea
- Stiff chest muscles after fast IV doses
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does fentanyl work?
Fentanyl, a synthetic lipophilic phenylpiperidine, selectively activates mu-opioid receptors. Its lipid solubility lets it work by injection, through the skin as a patch, and through the lining of the mouth or nose. CYP3A4 breaks it down, so CYP3A4 inhibitors can raise it to fatal levels.
Like other opioid analgesics: Opioids activate mu-opioid receptors, the G protein-coupled receptors used by the body's own opioids in the brain, spinal cord and gut. In nerve cells this opens potassium channels and closes calcium channels, so neurons fire less and release less pain transmitter such as substance P. They also depress the brainstem breathing center, narrow the pupils and slow the gut; tolerance and dependence build with regular use.
Uses
What is fentanyl used for?
- Pain relief during and after surgery
- Adjunct to general and regional anesthesia
- Cancer pain
- Long-term severe pain in opioid-tolerant patients
Side effects
Side effects of fentanyl
- Slowed breathing and apneaKnown forSerious
- Stiff chest muscles after fast IV dosesKnown forSerious
- Nausea and vomiting
- Drowsiness
- Dizziness
- Constipation
- Headache
- Slow heart rateSerious
- Low blood pressureSerious
- Addiction, misuse and dependenceSerious
- Withdrawal symptoms if stopped suddenly
- Serotonin syndrome with serotonergic drugsSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Patches are contraindicated in people who are not opioid-tolerant and for short-term, mild or post-operative pain.
- CYP3A4 inhibitors such as ritonavir, ketoconazole or erythromycin can raise levels to a fatal overdose.
- Fever or heat on a patch speeds absorption and can cause overdose; monitor for sedation and slowed breathing.
- Chest wall rigidity after rapid IV doses is managed with a neuromuscular blocker.
Good to know: Most common serious reactions to the injection are respiratory depression, apnea, muscle rigidity and slow heart rate, which is why it is given where breathing can be supported.
Remember it
A way to remember it
MORPHINE
- M
- Miosis (pinpoint pupils)
- O
- Opioid withdrawal if stopped suddenly
- R
- Respiratory depression
- P
- Pruritus (itching)
- H
- Hypotension
- I
- Intestinal slowing: constipation
- N
- Nausea and vomiting
- E
- Euphoria, then dependence and addiction
Written for biofideX
Its class
Opioid analgesics
Easily mixed up with opioid antagonists, benzodiazepines and antimotility drugs.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Fentanyl citrate injection: label (DailyMed)
- Fentanyl transdermal system: label (DailyMed)
- Fentanyl (NCI Thesaurus)
- Fentanyl (NHS)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Pain, fever and inflammation
Fentanyl is one of 15 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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