What is Fentanyl? What is Fentanyl used for?
Fentanyl is a Generic name for a very potent opioid drug that has a rapid onset and short duration of action that is used to treat severe chronic, “around-the-clock” pain. It should be used only for patients who have toleration to opioids drugs or who are already taking opioid pain medications regularly, such as morphine or oxycodone. Fentanyl is also used as an adjunct therapy to general anesthetics, and as an anesthetic for induction and maintenance. This synthetic substance is 50-100 times potent than morphine. It works primarily as a strong agonist of mu – opioid receptors.
Fentanyl is available as a transdermal patch, sublingual tablet, buccal tablet, lozenges, sublingual and nasal solution, spray. It can be also used intravenously. FDA first approved fentanyl in 1968 produced by Johnson & Johnson. Fentanyl is available under different Brand names and forms. Duragesic is a transdermal form of fentanyl that comes as a transdermal patch. Actiq is a Brand name for lozenges that contain fentanyl; Abstral is a sublingual tablet, Onsolis is a film that’s applied to the inner lining of the lip or cheek, Fentora is a buccal tablet, Lazanda is a nasal spray, and Subsys is a sublingual spray.
How long does Fentanyl stay in your system?
The elimination half-life of fentanyl depends on the way of its administration. If it is administrated intravenously it will result in quicker elimination from plasma compared to transdermal or transmucosal formats.
Half-life time of intravenously administrated fentanyl is approximately 2 to 4 hours, so it takes approximately 11 to 22 hours for complete elimination from the plasma. Transdermal patches with fentanyl and also transmucosal fentanyl – lozenges have half-lives of about 7 hours, so it takes about 1.6 days to be fully eliminated from the plasma after discontinuation. Different data shows that there is a greater difference between transmucosal and transdermal fentanyl in their elimination half-life. One finding shows that transdermal form has a longer median elimination half-life time at around 17 hours (range of 13 to 22 hours) and transmucosal fentanyl has a shorter half-life time at around 6.6 hours (range of 5 to 15 hours). If results are right, it would take around 3.9 days to eliminate the transdermal form of administered fentanyl and approximately 1.5 days to eliminate the transmucosal one.
To summarize, intravenously administrated fentanyl will be rapidly eliminated after discontinuation. The transdermal and transmucosal forms of fentanyl will take longer time to eliminate, but both will be out the body within 5 days after discontinuation. However, it is likely that the transmucosal fentanyl has a faster elimination than the transdermal form.
What factors may influence on how long Fentanyl stays in your body?
Many factors may have an impact on Fentanyl elimination from the body. Those factors can be following:
- Age: Younger individuals have a faster elimination of fentanyl compared to elderly (ages 65+). One study showed that after intravenous administration of fentanyl elimination half-life was 15.75 hours compared to just 4.42 hours in younger adults
- Body fat %: Studies suggests that individuals with a high percentage of body fat will likely retain fentanyl for a longer period after discontinuation compared to those with low body fat. This is because, fentanyl is highly lipophilic and soluble in fat tissue thus fentanyl distribution in fats is more extensive, and accumulation is greater.
- Genetics: Some people are known to be “fast metabolizers” of drugs while others are “slow metabolizers.” Slow metabolizers have reduced CYP3A4 isoenzyme function and may exhibit higher levels of fentanyl in their body.
- Liver function: Suboptimal or impaired liver function is linked with poor clearance of various drugs. A person with impaired liver function, especially those with hepatitis or cirrhosis will have a problem to metabolize and eliminate adequate amounts of fentanyl – which could result in toxicity.
- Hydration: The major route of fentanyl metabolites elimination is within urine. Staying well-hydrated can increase urinary flow rate, thus increasing drug excretion.
- Fentanyl dosage: The greater dose of fentanyl is taken the longer time is expected to stay in body system. Fentanyl transdermal patches are usually administrated in doses ranging from 12 mcg/hr to 100 mcg/hr, while the transmucosal fentanyl doses are ranging from 200 mcg to 1600 mcg. High doses of fentanyl may have a stronger impact on liver CYP3A4 enzymes, resulting in slower metabolism and ultimately longer retention in the body.
- Frequency of use: Frequent use of fentanyl in high doses will result in a greater degree of metabolite accumulation in the body.
- Taking other drugs or substances: Some drugs may inhibit the liver’s ability to metabolize fentanyl, possibly causing fentanyl to stay in body longer than it should be, while other drugs may have opposite effects. If fentanyl is taken together with CYP3A4 inhibitors drugs such as: Clarithromycin, Ketoconazole, Nelfinavir, Indinavir and Ritonavir, fentanyl metabolism will be reduced and elimination will be prolonged. In other hand, if it is taken together with CYP3A4 inducers such as Carbamazepine, Oxcarbazepine, Modafinil, Phenytoin, Phenobarbital, Rifampicin, and St. John’s wort, fentanyl metabolism will be altered and excreted at a faster rate than usual.
Fentanyl side effects
Fentanyl’s most common side effects include:
- Nausea, vomiting, constipation, and diarrhea
- Drowsiness and dizziness
- Increased sweating
- Feeling cold
Less common side effects after fentanyl use which may be severe, include:
- Muscle spasms and tremors
- Abnormally slow heart action
- Fluid retention and swelling of tissues in the lower limbs
- Anxiety, confusion, and hallucinations
- Abdominal pain
- Urinary problems
Rare side effects that are also reported after fentanyl use may include:
- Eczema and other skin disorders
- Sexual and erectile dysfunction
- Reduced sense of touch
- Flu-like symptoms
Discontinuing fentanyl suddenly may result in withdrawal symptoms such as:
- Restlessness, yawning, and difficulty falling asleep or staying asleep
- Sweating and chills
- Teary eyes and runny nose
- Muscle, joint, and back pain
- Irritability and anxiety
- Enlarged pupils
- Stomach cramps, nausea, loss of appetite, vomiting, and diarrhea
- Fast heartbeat and rapid breathing
Fentanyl may interact with:
- Monoamine oxidase inhibitors such as phenelzine (Nardil) and isocarboxazid (Marplan)
- Partial agonist analgesics, such as buprenorphine (Buprenex)
- Agonist/antagonist analgesics, such as pentazocine (Talwin) and butorphanol (Stadol)