Fentanyl – Background, Overdose, and Uses


Fentanyl, a potent opioid agonist, was developed in the 1950s to fill a need for strong and rapid analgesia.8 Because of these characteristics, fentanyl is commonly used to treat chronic cancer pain or in anesthesia. Fentanyl is related to other opioids like morphine and oxycodone.

Fentanyl’s high potency has also made it a common adulterant in illicit drugs, especially heroin.8 In 2017, 47600 overdose deaths in the United States involved some opioid (over 2/3 of all overdose deaths). Opioid overdoses kill an average of 11 Canadians daily. Fentanyl was FDA approved in 1968.

Properties and characteristics of Fentanyl

Drug class Opioid analgesics
Brand Names Abstral, Actiq, Duragesic, Effentora, Fentora, Instanyl, Lazanda, Sublimaze, Subsys
Synonyms Fentanil, Fentanila, Fentanilo, Fentanyl, Fentanyl CII, Fentanylum, Phentanyl
Molecular Formula C22H28N2O
Molecular Weight 336.5 g/mol
IUPAC Name N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide
Structural formula of main components
Pure active ingredient Fentanyl Hydrochloride
Appearance Crystals
Melting point 85.2 °C
Solubility In water, 200 mg/L at 25 °C
Excretion Fentanyl is excreted in the urine
Storage Store this drug at room temperature between 68°F and 77°F (20°C and 25°C)
Available Forms Tablet
Prescription Do not consume without the doctors’ advice

What is fentanyl used for?

Fentanyl is used to treat acute (short term), severe pain caused by major trauma or surgery, as well as for chronic pain caused by cancer.

How long you need to take fentanyl for will depend on why it has been prescribed. For example, fentanyl patches for cancer pain or in people receiving palliative care are approved for life-long use, while fentanyl used in acute pain or anaesthesia will be used only for a short time.

What side effects can this medication cause?

Fentanyl patches may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • Headache
  • Mood changes
  • Feeling cold
  • Drowsiness
  • Depression
  • Difficulty falling asleep or staying asleep
  • Uncontrollable shaking of a part of the body
  • Pain, burning, tingling, or numbness in the hands or feet
  • Dry mouth
  • Stomach pain
  • Indigestion
  • Back pain
  • Difficulty urinating
  • Itching
  • Skin irritation, redness, itching, or swelling in the area where you wore the patch

Some side effects can be serious. If you experience any of the below symptoms, call your doctor immediately:

  • Changes in heartbeat
  • Agitation, hallucinations (seeing things or hearing voices that do not exist), fever, sweating, confusion, fast heartbeat, shivering, severe muscle stiffness or twitching, loss of coordination, nausea, vomiting, or diarrhea
  • Nausea, vomiting, loss of appetite, weakness, or dizziness
  • Inability to get or keep an erection
  • Irregular menstruation
  • Decreased sexual desire
  • Chest pain
  • Seizure
  • Rash
  • Hives
  • Swelling of the eyes, face, mouth, tongue, throat, arms, hands, feet, ankles, or lower legs
  • Hoarseness
  • Difficulty breathing or swallowing

Fentanyl patches may cause other side effects. Call your doctor if you have any unusual problems while you are using fentanyl patches.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA).

Mechanism of action

Fentanyl binds to opioid receptors, especially the mu opioid receptor, which are coupled to G-proteins. Activation of opioid receptors causes GTP to be exchanged for GDP on the G-proteins which in turn down regulates adenylate cyclase, reducing concentrations of cAMP.6 Reduced cAMP decreases cAMP dependant influx of calcium ions into the cell. The exchange of GTP for GDP results in hyperpolarization of the cell and inhibition of nerve activity.

What may interact with this medication?

Do not take this medication with any of the following:

  • Mifepristone

This medication may also interact with the following:

  • Alcohol
  • Antihistamines for allergy, cough and cold
  • Antiviral medications for HIV or AIDS
  • Atropine
  • Certain antibiotics like clarithromycin, erythromycin, rifampin
  • Certain medications for anxiety or sleep
  • Certain medications for bladder problems like oxybutynin, tolterodine
  • Certain medications for blood pressure, heart disease, irregular heart beat
  • Certain medications for depression like amitriptyline, fluoxetine, sertraline
  • Certain medications for diabetes like pioglitazone, troglitazone
  • Certain medications for fungal infections like ketoconazole and itraconazole
  • Certain medications for migraine headache like almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, sumatriptan, zolmitriptan
  • Certain medications for nausea or vomiting like aprepitant, dolasetron, granisetron, ondansetron
  • Certain medications for seizures like phenobarbital, phenytoin, primidone
  • Certain medications for stomach problems like dicyclomine, hyoscyamine
  • Certain medications for travel sickness like scopolamine
  • Certain medications for Parkinson’s disease like benztropine, trihexyphenidyl
  • Cimetidine
  • Diuretics
  • General anesthetics like halothane, isoflurane, methoxyflurane, propofol
  • Grapefruit juice
  • Ipratropium
  • Linezolid
  • Local anesthetics like lidocaine, pramoxine, tetracaine
  • MAOIs like Carbex, Eldepryl, Marplan, Nardil, and Parnate
  • Medications that relax muscles for surgery
  • Methylene blue
  • Other narcotic medications for pain or cough
  • Phenothiazines like chlorpromazine, mesoridazine, prochlorperazine, thioridazine
  • St. John’s wort
  • Steroid medications like prednisone or cortisone

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

How to take fentanyl?

The fentanyl dosage your doctor prescribes will depend on several factors. These include:

  • The type and severity of the condition you’re using fentanyl to treat
  • Your age
  • The form of fentanyl you take
  • Other medical conditions you may have
  • Whether you have used opioids before
  • Your tolerance levels

Typically, your doctor will start you on a low dosage and adjust it over time to reach the dosage that’s right for you. They’ll ultimately prescribe the smallest dosage that provides the desired effect.

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to suit your needs.

Forms and strengths

  • Generic: fentanyl
    • Form: transdermal patch
    • Strengths: 12.5 micrograms (mcg)/hour, 25 mcg/hour, 37.5 mcg/hour, 50 mcg/hour, 62.5 mcg/hour, 75 mcg/hour, 87.5 mcg/hour, and 100 mcg/hour
  • Brand: Duragesic
    • Form: transdermal patch
    • Strengths: 12.5 mcg/hour, 25 mcg/hour, 37.5 mcg/hour, 50 mcg/hour, 75 mcg/hour, and 100 mcg/hour

Dosage for severe chronic pain

Adult dosage (ages 18–64 years)

  • Your doctor will base your starting dosage on the type of drug and dosage you currently take to control pain. Your doctor will prescribe the least amount of fentanyl to control your pain, with the least amount of side effects.
  • Your doctor may increase your dosage based on your level of pain. Your dosage won’t be increased sooner than 3 days after you take your first dose. After that, your doctor may increase your dosage every 6 days as needed.
  • Your doctor will regularly check to see if you still need to keep using this drug.
  • You should change your patch every 72 hours.

Child dosage (ages 2–17 years)

  • Your doctor will base your child’s starting dosage on the type of drug and dosage your child currently takes to control pain. Your doctor will prescribe the least amount of fentanyl to control your child’s pain, with the least amount of side effects.
  • Your doctor may increase your child’s dosage based on your child’s level of pain. The dosage won’t be increased sooner than 3 days after your child takes the first dose. After that, your doctor may increase the dosage every 6 days as needed.
  • Your doctor will regularly check to see if your child still needs to keep using this drug.
  • You should change your child’s patch every 72 hours.

Child dosage (ages 0–1 years)

Fentanyl transdermal patch hasn’t been established as safe or effective for use in children younger than 2 years.

Senior dosage (ages 65 years and older)

The kidneys of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stay in your body for a longer time. This increases your risk of side effects.

Your doctor may start you on a lowered dosage or a different dosing schedule. This can help keep levels of this drug from building up too much in your body.

Special dosage considerations

  • For people with liver disease: Your doctor may start with half the usual dose or avoid use, depending on how severe your disease is.
  • For people with kidney disease: Your doctor should start with half the usual dose or avoid use, depending on how severe your disease is.

Fentanyl and Overdose

Fentanyl and other synthetic opioids are the most common drugs involved in overdose deaths.1 Even in small doses, it can be deadly. Over 150 people die every day from overdoses related to synthetic opioids like fentanyl.

Drugs may contain deadly levels of fentanyl, and you wouldn’t be able to see it, taste it, or smell it. It is nearly impossible to tell if drugs have been laced with fentanyl unless you test your drugs with fentanyl test strips.

Test strips are inexpensive and typically give results within 5 minutes, which can be the difference between life or death. Even if the test is negative, take caution as test strips might not detect more potent fentanyl-like drugs, like carfentanil.

Signs of overdose

Recognizing the signs of opioid overdose can save a life. Here are some things to look for:

  • Small, constricted “pinpoint pupils”
  • Falling asleep or losing consciousness
  • Slow, weak, or no breathing
  • Choking or gurgling sounds
  • Limp body
  • Cold and/or clammy skin
  • Discolored skin (especially in lips and nails)

Warnings of Fentanyl

Fentanyl can slow or stop your breathing, and may be habit-forming. Misuse of Narcotic Medicine can cause Addiction, Overdose, or Death, especially in a child or other person using the medicine without a prescription.

Using this medicine during pregnancy may cause life-threatening withdrawal symptoms in the newborn.

Fatal side effects can occur if you use this medicine with alcohol, or with other drugs that cause drowsiness or slow your breathing.

Before taking this medicine

You should not use fentanyl unless you are already being treated with a similar opioid pain medicine and your body is tolerant to it. Talk with your doctor if you are not sure you are opioid-tolerant.

You should only use or take fentanyl if you have your own personal prescription for this medicine. You should not use fentanyl if you are allergic to it, or if you have:

  • Severe asthma or other breathing problems; or
  • A stomach or bowel obstruction (including paralytic ileus).

To make sure fentanyl is safe for you, tell your doctor if you have ever had:

  • Breathing problems, sleep apnea;
  • A head injury, brain tumor, or mental illness;
  • Alcoholism or drug addiction;
  • Urination problems;
  • A seizure disorder;
  • Liver or kidney disease; or
  • Problems with your gallbladder, pancreas, or thyroid.

If you are using fentanyl patches, tell your doctor if you have been sick with a fever. Having a high temperature can increase the amount of drug you absorb through your skin.

Do not change to another form of fentanyl eg injection, skin patch, dissolving film, or “lollipop” device. If you switch from another form of fentanyl, you will not use the same dose.

Pregnancy and Breastfeeding

If you use opioid medicine while you are pregnant, your baby could become dependent on the drug. This can cause life-threatening withdrawal symptoms in the baby after it is born. Babies born dependent on opioids may need medical treatment for several weeks.

Do not breastfeed while you are using fentanyl.

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