Fentanyl tablets belong to the group of medications called opioids. It is used to manage breakthrough pain for people with cancer who are 18 years of age and older and who are already receiving opioid medication (e.g., morphine, hydromorphone, fentanyl patches, oxycodone) for constant cancer pain. Breakthrough pain is pain that occurs despite taking regular doses of opioid pain medication for constant cancer pain.

This medication should not be used to treat other types of pain because it can cause life-threatening breathing problems for people who are not taking opioid medication chronically to manage cancer pain. This medication acts on the brain to relieve pain.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful (and even result in death) for people to take this medication if their doctor has not prescribed it.

This medication should only be prescribed by doctors that are knowledgeable about using opioids (e.g., morphine, hydromorphone, oxycodone) for cancer pain. Before starting this medication, your pain control should be stabilized with opioid medications.

The initial dose of this medication must always be one 100 µg (microgram) tablet placed under the tongue or above a back molar between the upper cheek and gum. Your doctor will adjust the dose of this medication until you get adequate pain relief with tolerable side effects. Your doctor will monitor you closely while finding the dose that works for you. The maximum dose of fentanyl sublingual tablets is 800 µg per dose.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

Do not take more of this medication than your doctor prescribed. Doing so could lead to serious and possibly life-threatening effects. If you do not have adequate pain relief after 30 minutes of taking a dose, do not take another dose of this medication. Your doctor will prescribe another pain medication for you to take if this happens.

Each dose of this medication should be separated by at least 4 hours and should not be used more than 4 times in one day. If you experience breakthrough pain more than 4 times in one day, contact your doctor as you may need to have the dose of long-acting opioid medication adjusted by your doctor. If your long-acting opioid dose changes, you doctor will reassess your dose of this medication.

Each fentanyl tablet is individually sealed in a child-resistant blister package. Do not open the package until you are ready to use this medication. If your mouth is dry, take a sip of water before taking this medication, but make sure your hands are dry before touching the tablet. To open the package, pull apart one of the blister units by tearing it along the perforations. Peel back the foil starting at the unsealed area and gently remove the tablet. Do not try to push the tablet out through the foil as this will damage the tablet.

Immediately place the tablet under your tongue on the floor of your mouth or above a back molar between the upper cheek and gum. It generally takes between 14 to 25 minutes for the tablet to dissolve. Do not eat or drink anything until the tablet has dissolved and you can no longer feel it in your mouth. After 30 minutes, if there is any fentanyl left in your mouth you may have a glass of water to help swallow any left over medicine. Do not break, cut, crush, chew, suck, or swallow this medication. Do not dissolve fentanyl tablets outside of the mouth.

It is important to take this medication exactly as prescribed by your doctor.

Store this medication in its original packaging at room temperature and protect it from moisture. Keep this medication in a safe place, away from children or pets, to prevent theft or misuse. Accidental use of even one dose of this medication, especially by children, can result in a fatal overdose of fentanyl. Do not take this medication in front of children.

When this medication is no longer needed, safely dispose of it by returning the medication to your pharmacist to be properly disposed of.

Do not take this medication if you:

• are allergic to fentanyl or any ingredients of this medication
• are allergic to other related opioid medications (e.g., meperidine)
• are experiencing acute alcoholism or delirium tremens (DTs)
• have not been taking other opioid medications (e.g., morphine, hydromorphone, oxycodone) regularly for constant cancer pain and your body is not used to regular opioid medication
• have mild or acute (short-term) pain (e.g., headache, migraine, dental pain) or pain related to surgery that can be treated with other pain medications
• have severe breathing problems or severe obstructive lung problems (e.g., chronic bronchitis, emphysema, status asthmaticus)
• are experiencing decreased, shallow breathing
• are currently taking or have taken a MAO inhibitor (e.g., phenelzine, tranylcypromine) within the past 14 days
• have severe depression of the central nervous system (i.e., sedation), a head injury, or increased pressure inside the brain
• have convulsive (seizure) disorders
• have a blockage or narrowing in the digestive system
• are experiencing sudden, severe abdominal pain that may require surgery (e.g., appendicitis, pancreatitis)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• constipation
• decreased appetite
• decreased ability or interest in sexual activity
• dizziness
• drowsiness
• dry mouth
• headache
• itching
• nausea
• sweating
• tiredness
• trouble sleeping
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• blockage in the bowel (e.g., severe constipation, nausea, abdominal pain)
• decreased coordination
• muscle weakness
• shortness of breath
• signs of low blood pressure, such as fainting, dizziness, or lightheadedness, especially when standing from a lying or sitting position
• signs of taking too much medication:
• trouble breathing
• extreme drowsiness with slowed breathing
• slow, shallow breathing
• feeling faint
• dizziness
• confusion
• inability to think, talk, or walk normally
• hallucinations
• tremors
• seizure
• slow, fast, pounding, or irregular heartbeat
• symptoms of withdrawal (e.g., nausea, vomiting, diarrhea, cold, clammy skin, body aches, decreased appetite, sweating)
• vision problems

Stop taking the medication and seek immediate medical attention if any of the following occur:

• seizures
• symptoms of overdose (e.g., trouble breathing; extreme drowsiness with slowed breathing; slow, shallow breathing; seizures; loss of consciousness)
• symptoms of a severe allergic reaction (e.g., hives; difficulty breathing; swelling of the face, mouth, throat, or tongue)
• symptoms of serotonin syndrome (e.g., confusion, fast heartbeat, hallucinations, increased body temperature, restlessness, shaking, shivering, sudden jerking of muscles, sweating)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abdominal (stomach) conditions: Like other narcotic medications, fentanyl may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. If you have a history of abdominal problems, such as slow movement of material through the digestive system, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Accidental use: Accidental ingestion or use of as little as one dose of fentanyl, in someone who it has not been prescribed for, can lead to a fatal overdose. Children are especially at risk. Keep this medication out of sight and reach of children. If a child accidentally ingests this medication, get immediate medical help.

Alcohol and other medications that cause drowsiness: Do not combine this medication with alcohol or other medications (e.g., antidepressants, sleeping pills, anxiety medications) that cause drowsiness, since additional drowsiness, sedation, coma, and possibly death can occur.

Blood pressure: Fentanyl can cause low blood pressure or make low blood pressure worse. If you experience severe dizziness, especially when standing from a lying or sitting position, contact your doctor.

Dependence: As with other opioid medications, physical dependence can occur when this medication is taken for long periods of time. This is not the same as addiction. Misuse of this medication is not usually a problem when it is used appropriately to treat pain. Consult your doctor if you have any questions.

Do not stop using fentanyl tablets suddenly, since withdrawal symptoms may occur. These symptoms include nausea, vomiting, body aches, diarrhea, shivering, and anxiety. Your doctor will advise you on how to safely stop taking fentanyl tablets.

It is important to tell your doctor if you, or a family member, have ever been dependent on or misused alcohol, prescription medications, or street drugs.

Difficulty breathing: Fentanyl tablets can cause serious and life-threatening breathing problems. If you experience slowed, shallow, or difficulty breathing, seek immediate medical attention. If you are taking other medications that can slow breathing (e.g., anxiety medications, sleeping pills) are a senior, or have chronic bronchitis or emphysema that is not severe, you are more at risk of experiencing these symptoms. Make sure you follow the instructions on how to properly use this medication. If you have any questions, contact your doctor or pharmacist. If you have a severe chronic lung condition (e.g., bronchitis, emphysema), you should not take this medication.

Drowsiness/reduced alertness: This medication may cause drowsiness or dizziness. Do not drive, operate machinery, or perform other potentially hazardous tasks until you have determined how this medication affects you.

Grapefruit: Do not drink grapefruit juice or eat grapefruit while you are taking this medication. This can interfere with how the medication leaves your body and cause unwanted and potentially serious side effects.

Head injury: People with head injuries, increased pressure in the brain, or reduced consciousness may have a higher risk of experiencing side effects (breathing problems) or worsening of their condition while taking this medication. Your doctor will weigh the risks and benefits of you using this medication and will monitor you closely for side effects.

Hormone changes: There have been reports of decreased hormone production by the adrenal glands when fentanyl is used for prolonged periods of time, usually longer than one month. These hormones affect many parts of the body, including how the body responds to stress. Symptoms of reduced hormone production by the body include nausea, vomiting, dizziness, fatigue, and decreased appetite. If you notice these symptoms, contact your doctor.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have reduced liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Other medical conditions: If you have lung problems, an abnormally slow heartbeat (bradycardia), gallstones, or pancreatitis (inflammation of the pancreas), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Proper use: It is important for you and people caring for you to understand how to use this medication correctly. If you experience, or your caregiver notices, the following symptoms of taking too much fentanyl, get immediate medical attention:

• difficulty thinking, talking, or walking
• extreme drowsiness with slowed breathing
• feeling faint, dizzy, confused
• hallucinations (hearing, seeing, or feeling things that are not there)
• seizures
• slow, shallow breathing
• trouble breathing

Serotonin syndrome: Severe reactions are possible when fentanyl is combined with medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors, which are used to treat depression. These combinations can cause an increase in the amount of serotonin in the body. Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, and changes in mental state including delirium and agitation. Coma and death are possible.

If you are taking antidepressants, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Tolerance: Fentanyl tablets may lead to tolerance when used for a long period of time. Tolerance means that your body gets used to the medication so that more medication may be needed to produce the same pain relief. Your doctor will recommend the dose of fentanyl tablets that is most appropriate for you. Do not change your dose or the way you are using the medication on your own. If you find that a dose of fentanyl is not providing the same amount of pain relief as before, contact your doctor.

If you experience a sudden, unexplained increase in pain, or feel unexpected pain, contact your doctor as soon as possible.

Pregnancy: Fentanyl crosses the placenta and may affect the developing baby if it is taken during pregnancy. Withdrawal symptoms have been noted in newborns of birth parents who used fentanyl during pregnancy. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant or plan to become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and taking fentanyl, it may cause life-threatening breathing difficulties for your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children and adolescents less than 18 years of age. Accidental ingestion of this medication by children may lead to severe and even fatal consequences. Keep this medication out of the reach of children.

Seniors: Seniors may be more sensitive to the side effects of this medication.

There may be an interaction between fentanyl tablets and any of the following:

• acetazolamide
• aclidinium
• alcohol
• alpha-agonists (e.g., clonidine, guanfacine)
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• antihistamines (e.g., azelastine, cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine, rupatadine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• apalutamide
• aprepitant
• atropine
• "azole" antifungals (e.g., fluconazole, itraconazole, ketoconazole, posaconazole)
• barbiturates (e.g., butalbital, phenobarbital)
• benzodiazepines (e.g., alprazolam, clonazepam, diazepam, lorazepam)
• benztropine
• beta-adrenergic blockers (e.g., atenolol, carvedilol, propranolol, sotalol)
• bosentan
• brimonidine
• bromocriptine
• buprenorphine
• buspirone
• butorphanol
• cannabis
• chloral hydrate
• clidinium
• clopidogrel
• cobicistat
• conivaptan
• darifenacin
• desmopressin
• dextromethorphan
• digoxin
• diltiazem
• dimenhydrinate
• diphenoxylate
• disopyramide
• diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
• domperidone
• donepezil
• dronedarone
• efavirenz
• entacapone
• enzalutamide
• ephedrine
• ergot-containing medications (e.g., dihydroergotamine, ergonovine, ergotamine)
• esketamine
• ethopropazine
• fesoterodine
• flibanserin
• flunarizine
• flecainide
• gabapentin
• galantamine
• general anesthetics (medications used to put people to sleep before surgery)
• glycopyrrolate
• grapefruit juice
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir)
• ipratropium
• ivabradine
• kava kava
• ketotifen
• lanreotide
• lemborexant
• lenacapavir
• letermovir
• linezolid
• lithium
• lumacaftor and ivacaftor
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methylene blue
• methylphenidate
• metoclopramide
• mifepristone
• mirtazapine
• mitotane
• modafinil
• monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, rasagiline, selegiline, tranylcypromine)
• modafinil
• muscle relaxants (e.g., cyclobenzaprine, baclofen, methocarbamol, orphenadrine)
• nabilone
• naloxone
• naltrexone
• nirmatrelvir and ritonavir
• octreotide
• olopatadine
• other opioid medications (e.g., meperidine, morphine, codeine, oxycodone, hydromorphone, tapentadol, tramadol)
• pasireotide
• pegvisomant
• perampanel
• pizotifen
• pomalidomide
• pramipexole
• prasugrel
• pregabalin
• propiverine
• prucalopride
• pseudoephedrine
• rifabutin
• rifampin
• rivastigmine
• ropinirole
• rotigotine
• scopolamine
• St. John's wort
• seizure medications (e.g., carbamazepine, clobazam,  levetiracetam, phenobarbital, phenytoin, primidone, topiramate, valproic acid)
• selective serotonin reuptake inhibitors (SSRI; e.g., fluoxetine, paroxetine, sertraline, vortioxetine)
• serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
• serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., desvenlafaxine, duloxetine, venlafaxine)
• solifenacin
• sphingosine 1-phosphate (S1P) receptor inhibitors (e.g., fingolimod, ozanimod, ponesimod, siponimod)
• spironolactone
• tetrabenazine
• thalidomide
• ticagrelor
• tiotropium
• tofacitinib
• tizanidine
• tolterodine
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• "triptan" migraine medications (e.g., almotriptan, eletriptan, rizatriptan, sumatriptan)
• trospium
• tyrosine kinase inhibitors (e.g., crizotinib, imatinib, lapatinib, nilotinib)
• tryptophan
• umeclidinium
• verapamil
• vilazodone
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.