Fentanyl dosage, forms, and strengths

Fentanyl is a potent prescription opioid pain reliever that is 100 times more powerful than morphine. Because of its potential hazards, healthcare professionals use fentanyl sparingly for only a few purposes, such as anesthesia, breakthrough cancer pain, or pain that is not adequately controlled by other opioids. Healthcare professionals administer fentanyl injections or prescribe fentanyl skin patches or oral fentanyl. 

Fentanyl forms and strengths

Fentanyl comes in many dosage forms:

• Injection: 50 mcg/mL

• Transdermal patch: 12 mcg/hour, 25 mcg/ hour, 37.5 mcg/hour, 50 mcg/hour, 62.5 mcg/hour, 75 mcg/hour, 87.5 mcg/hour, 100 mcg/hour

• Transmucosal lozenges: 200 mcg, 400 mcg, 600 mcg, 800 mcg, 1200 mcg, 1600 mcg

• Buccal tablets: 100 mcg, 200 mcg, 400 mcg, 600 mcg, 800 mcg

Fentanyl dosage for adults

The FDA has approved fentanyl as a pain medication for severe pain, breakthrough cancer pain, and medical procedures. 

Fentanyl is a potentially hazardous medication and can never be given to people with:

• Known allergies to fentanyl

• Respiratory depression or obstructive airway disease

• Gastrointestinal obstruction

• Paralytic ileus

• Liver failure 

Fentanyl patches, lozenges, and tablets are never prescribed to people who are not already taking an opioid pain reliever.

Fentanyl may cause serious problems in people with chronic lung disease, debilitation, head injury, brain tumors, impaired consciousness, coma, circulatory shock, adrenal gland problems, mental illness, or a substance use disorder.

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Fentanyl dosage for pain

Fentanyl patches are prescribed to treat persistent pain that cannot be adequately treated with any other pain medication. Because of the risk of serious side effects, only people who are currently taking opioids can safely use a fentanyl patch. The dose prescribed will be based on the daily dose of the current opioid being taken for pain management. 

• Standard fentanyl dosage for pain relief: 25–100 mcg/hr transdermal patch worn for up to 72 hours

• Maximum recommended fentanyl dosage for pain relief: 300 mcg/hr transdermal patches (three 100 mcg/hr patches) worn for up to 72 hours

Fentanyl dosage for breakthrough cancer pain

Cancer can be an incredibly painful experience, both physically and emotionally. The severity of physical pain can vary depending on the type and stage of cancer, but occasionally the pain dramatically worsens over time. Called breakthrough pain (as opposed to background or chronic pain), it can be very severe and debilitating. People are normally prescribed opioid pain medications to manage background pain, but doctors add fentanyl to use as needed for breakthrough pain. 

Unlike a patch, people prescribed fentanyl for breakthrough pain take doses as they need them. Taken either as a lozenge or buccal tablet, the dose is placed in the mouth and slowly melts so that the fentanyl is absorbed beneath the tongue or in the tissues lining the mouth. In this way, the dose of fentanyl begins to work almost right away.

Doses are taken at the outset of a breakthrough pain episode. If the first dose does not work well enough, another dose can be taken 30 minutes later. No more than two doses can be taken per episode. 

If there’s another pain episode, a third dose can’t be taken until four hours after the last dose. Again, the next dose for that pain episode can be taken 30 minutes later. Added up, that means that people should not take more than eight doses every 24 hours.

Because the dosage strengths are not equivalent, lozenges and buccal tablets cannot be substituted for one another without getting another prescription.

• Standard fentanyl dosage for breakthrough cancer pain: 100–800 mcg buccal tablet taken 30 minutes apart OR 200–1,600 mcg lozenge taken 30 minutes apart

• Maximum fentanyl dosage for breakthrough cancer pain: No more than two doses for each pain episode and no more than eight doses in a 24-hour period

Fentanyl dosage for medical procedures

Fentanyl is also used to provide pain relief and sedation for medical procedures, including both inpatient and outpatient surgery. Fentanyl injections are administered by anesthesiologists or other doctors. 

Doctors may administer a dose of fentanyl before anesthesia, as an add-on anesthesia, as a general anesthetic, or for pain management following a procedure. Low doses are used for minor procedures. High doses are reserved for major surgeries and may require ventilation to sustain breathing. 

• Standard fentanyl dosage as premedication before a medical procedure: 50–100 mcg intramuscular or slow intravenous injection 30–60 minutes before anesthesia

• Standard fentanyl dosage as an adjunct to general anesthesia: 2–50 mcg/kg injection

• Standard fentanyl dosage as an adjunct to regional anesthesia: 50–100 mcg intramuscular or slow intravenous injection

• Standard fentanyl dosage as general anesthesia (for open heart surgery): 50–150 mcg/kg 

• Standard fentanyl dosage for postoperative pain relief: 50–100 mcg intramuscular or slow intravenous injection

Fentanyl dosage for children

Fentanyl citrate injections and fentanyl patches are FDA approved for use in children as young as 2 years of age. The FDA has not approved the use of fentanyl buccal tablets in children younger than 18 years of age or the use of fentanyl lozenges in children younger than 16 years of age. Fentanyl lozenge doses for adolescents 16 years of age and older are the same as for adults.

As in adults, doctors use fentanyl citrate injections in children for medical procedures from simple procedures to major surgery. Doses are based on weight.

Healthcare professionals prescribe fentanyl patches for severe pain in children already taking an opioid. The dose of fentanyl will depend on the type and daily dosage of the opioid being used. 

• Standard fentanyl injection dosage for children ages 2 and older: 2–3 mcg/kg injection

• Standard fentanyl patch dosage for children ages 2 and older: Dosage depends on current opioid therapy

Fentanyl dosage restrictions

When using fentanyl patches, doctors will reduce the dose by half for people with mild to moderate liver or kidney impairment. Doctors avoid using fentanyl patches in people with severe hepatic impairment or severe renal impairment.

No specific dosage modifications are required for people receiving fentanyl injections, lozenges, or buccal tablets, though individual doctors will base the dose based on the person’s response to the medication and the degree of impairment. 

Fentanyl dosage for pets 

Veterinarians use fentanyl injections for veterinary procedures and fentanyl patches for analgesia.

Injections are made and supervised by a veterinarian before anesthesia, during surgery, or after surgery to manage pain. Doses are based on the pet’s body weight.

Veterinarians prescribe fentanyl patches to dogs and cats for chronic pain, dull pain, or pain due to veterinary conditions such as cancer or pancreatitis. The veterinarian will usually put the patch on the animal in the clinic, but they may give instructions for the owner to place the patch. 

Fentanyl patch dosages are based on weight:

• Standard fentanyl dosage for cats and small dogs weighing less than 10 kg: 25 mcg/hr patch

• Standard fentanyl dosage for dogs 10–20 kg: 50 mcg/hr patch

• Standard fentanyl dosage for dogs 20–30 kg: 75 mcg/hr patch

• Standard fentanyl dosage for dogs >30 kg: 100 mcg/hr patch

How to take fentanyl

People who take fentanyl will either use a patch or take lozenges or buccal tablets. None of these are typical dosage forms, so people should read the instructions carefully: 

• Take this medication as directed. 

• Do not take more than prescribed or take doses more often than prescribed.

• Tell the doctor about all the prescription drugs, over-the-counter medications, and supplements being taken before starting fentanyl treatment.

• Please read the Medication Guide and Instructions for Use that come with the prescription.

• Do not substitute one fentanyl product for another. The doses are not equivalent.

• Do not stop using fentanyl products until talking to a healthcare provider. The dose may need to be tapered gradually to prevent withdrawal symptoms.

• How to use fentanyl patches:

  • Fentanyl patches are only used for severe pain in people already taking an opioid pain medication. 

  • The prescriber will tell you how many patches to use, where to apply them, and how often to apply them. 

  • Before opening the protective pouch, remove the old patch and fold it up so the two glued halves stick together. Immediately flush it down the toilet.

  • Only remove a fentanyl patch from its protective pouch when ready to apply the patch.

  • Always make sure that the dose written on the patch is the dose you’ve been prescribed.

  • Tear the wrapper open carefully. NEVER CUT the wrapper or the patch with scissors. 

  • Do not use any patch if the pouch seal is broken or the patch has been cut or damaged.

  • If any medicine leaks directly onto your skin, wash it off immediately. 

  • Use a different spot on the skin to place the new patch. Do not put the patch on skin that is burned, cut, or irritated. 

  • When finished, immediately wash your hands.

  • Wear the patch for three (3) days (72 hours) and then remove it and immediately dispose of it.

  • If the patch falls off at any time, dispose of it immediately and apply a new patch.

  • You can bathe, shower, or swim, but do not use hot tubs, saunas, tanning beds, tanning lamps, electric blankets, or heating pads over the patch. Do not exercise hard or sunbathe. 

  • If you forget to wear or change a patch, put one on as soon as possible. Wear the replacement patch for no longer than three (3) days (72 hours). 

  • Store the patches at room temperature in the original package. Put the package in a secure and locked area out of the reach of children and other people.

• How to take fentanyl lozenges and buccal tablets:

  • Fentanyl lozenges and buccal tablets are only used for cancer breakthrough pain. 

  • Continue taking any round-the-clock opioid (such as oxycodone or morphine) prescribed for the cancer pain.

  • Use only one dose per breakthrough pain episode.

  • If the dose isn’t effective after 30 minutes, take one more dose. Do not take more than two doses for any single breakthrough pain episode.

  • If the pain doesn’t improve 30 minutes after the second dose, call the healthcare provider.

  • For any new episode of breakthrough pain, you must take the first dose at least four hours after you have taken the last dose for the previous episode.

  • The fentanyl dose is absorbed through the tissues in the mouth.

  • Put the lozenge in your mouth and allow it to melt for 15 minutes.

  • If it takes less than 15 minutes, you won’t get the full dose.

  • Put the buccal tablet in your mouth and allow it to completely dissolve.

  • Chewing, breaking, or swallowing the tablet will mean you don’t get the full dose.

  • If you feel dizzy, sleepy, or have stomach problems before the tablet or lozenge is dissolved, spit it out into a sink or toilet and immediately flush it down.

Fentanyl dosage FAQs

How do I stop taking fentanyl?

Do not stop taking fentanyl until consulting with the prescriber. 

The abrupt discontinuation of any synthetic opioid like fentanyl could cause severe withdrawal symptoms such as muscle pain, anxiety, restlessness, sweating, and gastrointestinal problems. 

Doctors often prescribe a steadily decreasing dose to wean people off opioid use. If fentanyl needs to be stopped quickly, healthcare professionals use drugs such as buprenorphine or methadone to ease the withdrawal process.

Can you overdose on fentanyl?

Because fentanyl is so powerful, even a tiny amount can cause a potentially fatal overdose. In fact, fentanyl is the main cause of opioid overdose deaths in the United States. Because of the risk, healthcare providers suggest that patients taking fentanyl carry naloxone to reverse the effects of a possible fentanyl overdose.

If too much fentanyl is taken, immediately administer naloxone, call a poison helpline, or get emergency medical help. Symptoms of an overdose include slowed breathing, sleepiness, stupor, coma, loss of muscle tone, cold, clammy skin, pinpoint pupils, slow heart rate, low blood pressure, airway obstruction, and unusual snoring.

What happens when you mix fentanyl and alcohol?

Do not drink alcohol when taking fentanyl or any other opioid analgesic. Do not take any other central nervous system depressants, such as benzodiazepines. The combination will worsen side effects such as sedation, dizziness, drowsiness, and low blood pressure (hypotension). More importantly, there’s a risk of respiratory depression (slow and shallow breathing), a potentially life-threatening adverse effect.

Is it safe to take fentanyl during pregnancy?

Tell the prescriber if you’re pregnant or get pregnant while taking fentanyl. The drug can be used short-term during pregnancy, but long-term use during pregnancy can result in babies being born with opioid withdrawal symptoms. 

Is it safe to take fentanyl while breastfeeding?

Breastfeeding is not recommended in women taking fentanyl. The drug is present in breast milk. There is a risk the baby can experience excessive sedation or respiratory depression. 

Sources

• Drug overdose deaths: Facts and figures, NIH National Institute on Drug Abuse

• Duragesic drug summary, Prescriber’s Digital Reference (PDR)

• Fentanyl buccal fentanyl citrate tablet prescribing information, DailyMed (NIH National Library of Medicine)

• Fentanyl citrate injection prescribing information, DailyMed (NIH National Library of Medicine)

• Fentanyl citrate lozenge prescribing information, DailyMed (NIH National Library of Medicine)

• Fentanyl extended-release patch prescribing information, DailyMed (NIH National Library of Medicine)

• Plumb’s Veterinary Drug Handbook, 7th ed

• Use of fentanyl as a patch and CRI, DVM 360