Fentanyl: 6 things you should know
Medically reviewed by C. Fookes, BPharm. Last updated on Nov 15, 2018.
1. How it works
- Fentanyl may be used to treat severe pain that is unresponsive to less potent pain-relief medicines (analgesics).
- Fentanyl is a full agonist at the mu receptor (full agonists have a larger effect at higher dosages). By binding to these receptors, pain signals are blocked on their way to the brain.
- Fentanyl belongs to the group of drugs known as opioids or opioid analgesics. Fentanyl may also be called a narcotic analgesic.
- Fentanyl is a very strong pain-relieving medicine used for the relief of moderate-to-severe pain that is unresponsive to less potent pain-relieving medicines.
- Available as an injection, transdermal patch or device, nasal spray, sublingual (under-the-tongue) tablet or spray, or buccal (beneath the cheek) tablet.
- Different formulations have different uses. For example, fentanyl injection may be used as part of anesthesia to help prevent pain after an operation or procedure. Fentanyl patches or transdermal devices may be used for moderate-to-severe pain that requires round-the-clock therapy. Sublingual sprays or tablets may be used for break-through type cancer pain.
- Note that doses are not equivalent between the different formulations (for example a 25mcg fentanyl patch DOES NOT EQUAL 25mcg of fentanyl injection). The substitution of one fentanyl product for a different type of fentanyl product (for example Subsys for Duragesic) may result in a fatal overdose.
- Fentanyl is a pure opioid agonist analgesic. This means that with increasing dosages, it provides increasing pain relief, unlike some other opioids that have a ceiling effect (plateau off above a certain dosage).
- Generic fentanyl is available.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Nausea, vomiting, constipation, sedation, dizziness, lack of energy, shortness of breath and abdominal distension.
- May also cause flushing, sweating, itching, red eyes and a drop in blood pressure on standing.
- Fentanyl is extensively metabolized through the liver when taken orally and as a consequence of this, fentanyl is not available in an oral formulation, although buccal (beneath the cheek) and sublingual (under the tongue) formulations exist. Buccal and sublingual formulations bypass the liver and enter straight into the bloodstream.
- Fentanyl should NOT be used in people who have never been prescribed an opioid analgesic (opioid-naive people).
- Fentanyl is usually only available from a certified pharmacy under a special program.
- Fentanyl is a schedule II controlled substance and is up to 100 times more potent than morphine on a weight for weight basis. Note that different sources cite different equivalent dosages; in reality there is a wide inter-individual variation between effective opioid dosages. Do not try to convert fentanyl on a weight-for-weight basis (for example from patch to injection using the same mcg dosage) because of an extremely high risk of over-dosage. It is always safer to underestimate fentanyl requirements.
- Because of the risk of addiction and dependence, fentanyl patches should only be used for severe, chronic pain that requires round-the-clock, long-term opioid treatment and for which other treatments have been ineffective. Other forms of fentanyl (such as sublingual spray or tablets) may be used for the relief of breakthrough pain. Fentanyl should not be used for acute or postoperative pain, or for headaches or migraines.
- Keep out of reach of children and pets. Death has been reported in children and pets who have accidentally ingested fentanyl products.
- Fatal breathing problems have occurred in patients given fentanyl products. The risk is higher in those who have not been administered opioids before.
- Fentanyl has a high potential for abuse and care must be taken to keep it hidden from drug seekers. Fentanyl is often used to lace counterfeit drugs - several deaths have been reported, for example, from Xanax-laced with fentanyl.
- May interact with other drugs, particularly ones that inhibit the metabolism of fentanyl through CYP3A4, such as ketoconazole, erythromycin and ritonavir, and those with similar side effects (such as respiratory depression, sedation). Fentanyl also interacts with other drugs that increase levels of serotonin (such as SSRIs, TCAs, triptans, tramadol).
- May affect your ability to drive and operate machinery. Avoid alcohol.
- May not be suitable for people with pre-existing respiratory disease, head injuries, bradycardia (slow heartbeat) and other conditions.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Ensure you dispose of all fentanyl products (such as used patches, empty spray canisters) carefully as although they may be empty they may still contain enough fentanyl to kill a child or an animal. Many products supply a charcoal-lined pouch in the carton to help with disposal.
- You need to be enrolled in the TIRF REMS Access program before you can receive fentanyl products such as Subsys. In addition, only pharmacies that are enrolled in the TIRF REMS Access program can dispense fentanyl.
- When used for break-through pain NEVER take more than two doses of short-acting fentanyl products (such as Subsys) at one time (each dose must be at least 30 minutes apart).
- Never share your fentanyl with anybody, as it may kill them due to overdose.
- Do not drive or operate machinery if you are sleepy or your reaction time is impaired after taking fentanyl.
- Do not mix fentanyl with alcohol, sleeping aids or tranquilizers unless prescribed by a doctor.
- Some fentanyl products are provided with a child-safety kit to help adults store them out of reach of children or pets.
- If you are taking sublingual fentanyl (Abstral), remove tablets from the blister and place on the floor of the mouth directly under the tongue. Do not chew, suck, or swallow Abstral tablets. Allow the tablet to completely dissolve in the sublingual cavity before eating or drinking anything. If you have a dry mouth, use water to moisten the tissues of the mouth BEFORE taking Abstral.
6. Response and Effectiveness
- Time to effect varies depending on formulation from 15-30 minutes (sublingual tablets), 46 minutes (buccal tablets), 1.5 hours (spray) to 3 hours (patch). Respiratory depressant effects can be seen from as early as 15-30 minutes after administration and persist for several hours.
- Fentanyl Buccal tablets [Package Insert] Revised 04/2017 Teva Pharmaceuticals USA, Inc. https://www.drugs.com/pro/fentanyl-buccal-tablets.html
- Abstral (fentanyl sublingual tablets) [Package Insert]. Revised: 05/2017. Sentynl Therapeutics, Inc https://www.drugs.com/pro/abstral-sublingual-tablet.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use fentanyl only for the indication prescribed.
Copyright 1996-2019 Drugs.com. Revision date: November 15, 2018.
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