Last updated on RxList: 3/25/2021
Fentora Side Effects Center

What Is Fentora?

Fentora (fentanyl citrate) is a narcotic (opioid) pain medicine used to treat "breakthrough" cancer pain that is not controlled by other medicines. Fentora is available in generic form.

What Are Side Effects of Fentora?

Common side effects of Fentora include:

Other side effects of Fentora include pain, mouth sores, or irritation in the mouth where the medication has been applied. Some side effects of Fentora may decrease after using this medication for a while. Tell your doctor if you have unlikely but serious side effects of Fentora including:

Dosage for Fentora

The initial dose of Fentora is always 100 mcg with the only exception being patients already using Actiq. Place the Fentroa tablet in your mouth above a rear molar tooth between your upper cheek and gum, and leave it in place until it is dissolved (usually 14 to 25 minutes). Do not break, bite, chew, suck, or swallow the tablet whole.

What Drugs, Substances, or Supplements Interact with Fentora?

Fentora may interact with cold or allergy medicine, sedatives, sleeping pills, muscle relaxers, and medicine for seizures, depression or anxiety, aprepitant, diltiazem, verapamil, antibiotics, antifungal medications, or HIV medicines. Tell your doctor all medications you use.

Fentora During Pregnancy and Breastfeeding

During pregnancy, Fentora should be used only when prescribed. Using it near the expected delivery date is not recommended because of potential for harm to the fetus. Babies born to mothers who have used this medication may have withdrawal symptoms such as irritability, abnormal/persistent crying, vomiting, or diarrhea. If you notice symptoms in your newborn, tell the doctor. This drug passes into breast milk and may rarely have undesirable effects on a nursing infant. Tell the doctor if your baby develops unusual sleepiness, difficulty feeding, or trouble breathing. Consult your doctor before breastfeeding. Withdrawal symptoms may occur if you suddenly stop using this medication.

Additional Information

Our Fentora (fentanyl citrate) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Skin Cancer Symptoms, Types, Images See Slideshow
Fentora Consumer Information

3 pharmacies near 20147 have coupons for fentora (Brand Names:Fentora for 200MCG)

Wegmans Food Markets Inc
Wegmans Food Markets Inc

Est. Regular Price


with free coupon

View Coupon

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Like other opioid medications, fentanyl can slow or stop your breathing. If your breathing gets too weak, death may occur.

Your caregivers will watch for any of these side effects, which may clear up within minutes after stopping the fentanyl infusion or decreasing the dose:

  • weak or shallow breathing;
  • fast or slow heart rate;
  • stiff muscles; or
  • severe weakness, feeling light-headed or fainting.

Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.

Common side effects may include:

  • slowed breathing;
  • slow heart rate;
  • muscle stiffness;
  • dizziness, vision problems;
  • nausea, vomiting;
  • itching, sweating; or
  • high blood pressure (confusion, anxiety, pounding in your neck or ears).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Fentora (Fentanyl Buccal Tablet)

Fentora Professional Information


The following serious adverse reactions are described, or described in greater detail, in other sections:

  • Life-Threatening Respiratory Depression [see WARNINGS AND PRECAUTIONS]
  • Interactions with Benzodiazepines and Other CNS Depressants [see WARNINGS AND PRECAUTIONS]
  • Addiction, Abuse, and Misuse [see WARNINGS AND PRECAUTIONS]
  • Neonatal Opioid Withdrawal Syndrome [see WARNINGS AND PRECAUTIONS]
  • Serotonin Syndrome [see WARNINGS AND PRECAUTIONS]
  • Adrenal Insufficiency [see WARNINGS AND PRECAUTIONS]
  • Severe Hypotension [see WARNINGS AND PRECAUTIONS]
  • Gastrointestinal Adverse Reactions [see WARNINGS AND PRECAUTIONS]

Clinical Studies Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The safety of FENTORA has been evaluated in 304 opioid-tolerant cancer patients with breakthrough pain. The average duration of therapy was 76 days with some patients being treated for over 12 months.

The clinical trials of FENTORA were designed to evaluate safety and efficacy in treating patients with cancer and breakthrough pain; all patients were taking concomitant opioids, such as sustained-release morphine, sustained-release oxycodone or transdermal fentanyl, for their persistent pain.

The adverse event data presented here reflect the actual percentage of patients experiencing each adverse effect among patients who received FENTORA for breakthrough pain along with a concomitant opioid for persistent pain. There has been no attempt to correct for concomitant use of other opioids, duration of FENTORA therapy or cancer-related symptoms.

Table 2 lists, by maximum dose received, adverse events with an overall frequency of 5% or greater within the total population that occurred during titration. The ability to assign a dose-response relationship to these adverse events is limited by the titration schemes used in these studies.

Table 2:  Adverse Events Which Occurred During Titration at a Frequency of ≥5%

System Organ Class
MeDRA preferred term, n (%)
100 mcg
200 mcg
400 mcg
600 mcg
800 mcg
Gastrointestinal disorders
Nausea 4 (9) 5 (15) 10 (19) 13 (23) 18 (16) 50 (17)
Vomiting 0 2 (6) 2 (4) 7 (13) 3 (3) 14 (5)
General disorders and administration site conditions
Fatigue 3 (7) 1 (3) 9 (17) 1 (2) 5 (4) 19 (6)
Nervous system disorders
Dizziness 5 (11) 2 (6) 12 (23) 18 (32) 21 (19) 58 (19)
Somnolence 2 (4) 2 (6) 6 (12) 7 (13) 3 (3) 20 (7)
Headache 1 (2) 3 (9) 4 (8) 8 (14) 10 (9) 26 (9)
*Three hundred and two (302) patients were included in the safety analysis.

Table 3 lists, by successful dose, adverse events with an overall frequency of ≥5% within the total population that occurred after a successful dose had been determined.

Table 3: Adverse Events Which Occurred During Long-Term Treatment at a Frequency of ≥5%

System Organ Class
MeDRA preferred term, n (%)
100 mcg
200 mcg
400 mcg
600 mcg
800 mcg
Blood and lymphatic system disorders
Anemia 6 (32) 4 (13) 4 (9) 5 (10) 7 (13) 26 (13)
Neutropenia 0 2 (6) 1 (2) 4 (8) 4 (7) 11 (6)
Gastrointestinal disorders
Nausea 8 (42) 5 (16) 14 (32) 13 (27) 17 (31) 57 (29)
Vomiting 7 (37) 5 (16) 9 (20) 8 (17) 11 (20) 40 (20)
Constipation 5 (26) 4 (13) 5 (11) 4 (8) 6 (11) 24 (12)
Diarrhea 3 (16) 0 4 (9) 3 (6) 5 (9) 15 (8)
Abdominal pain 2 (11) 1 (3) 4 (9) 7 (15) 4 (7) 18 (9)
General disorders and administration site conditions
Edema peripheral 6 (32) 5 (16) 4 (9) 5 (10) 3 (5) 23 (12)
Asthenia 3 (16) 5 (16) 2 (5) 3 (6) 8 (15) 21 (11)
Fatigue 3 (16) 3 (10) 9 (20) 9 (19) 8 (15) 32 (16)
Infections and infestations
Pneumonia 1 (5) 5 (16) 1 (2) 1 (2) 4 (7) 12 (6)
Weight decreased 1 (5) 1 (3) 3 (7) 2 (4) 6 (11) 13 (7)
Metabolism and nutrition disorders
Dehydration 4 (21) 0 4 (9) 6 (13) 7 (13) 21 (11)
Anorexia 1 (5) 2 (6) 4 (9) 3 (6) 6 (11) 16 (8)
Hypokalemia 0 2 (6) 0 1 (2) 8 (15) 11 (6)
Musculoskeletal and connective tissue disorders
Back pain 2 (11) 0 2 (5) 3 (6) 2 (4) 9 (5)
Arthralgia 0 1 (3) 3 (7) 4 (8) 3 (5) 11 (6)
Neoplasms benign, malignant and unspecified (including cysts and polyps)
Cancer pain 3 (16) 1 (3) 3 (7) 2 (4) 1 (2) 10 (5)
Nervous system disorders
Dizziness 5 (26) 3 (10) 5 (11) 6 (13) 6 (11) 25 (13)
Headache 2 (11) 1 (3) 4 (9) 5 (10) 8 (15) 20 (10)
Somnolence 0 1 (3) 4 (9) 4 (8) 8 (15) 17 (9)
Psychiatric disorders
Confusional state 3 (16) 1 (3) 2 (5) 3 (6) 5 (9) 14 (7)
Depression 2 (11) 1 (3) 4 (9) 3 (6) 5 (9) 15 (8)
Insomnia 2 (11) 1 (3) 3 (7) 2 (4) 4 (7) 12 (6)
Respiratory, thoracic, and mediastinal disorders
Cough 1 (5) 1 (3) 2 (5) 4 (8) 5 (9) 13 (7)
Dyspnea 1 (5) 6 (19) 0 7 (15) 4 (7) 18 (9)

In addition, a small number of patients (n=11) with Grade 1 mucositis were included in clinical trials designed to support the safety of FENTORA. There was no evidence of excess toxicity in this subset of patients.

Application Site Reactions: In clinical trials, 10% of all patients exposed to FENTORA reported application site reactions. These reactions ranged from paresthesias to ulceration and bleeding. Application site reactions occurring in ≥1% of patients were pain (4%), ulcer (3%), and irritation (3%). Application site reactions tended to occur early in treatment, were self-limited and only resulted in treatment discontinuation for 2% of patients.

The duration of exposure to FENTORA varied greatly, and included open-label and double-blind studies. The frequencies listed below represent the ≥1% of patients (and not listed in Tables 2 and 3 above) from three clinical trials (titration and post-titration periods combined) who experienced that event while receiving FENTORA. Events are classified by system organ class.

Adverse Events (≥1%)

Blood and Lymphatic System Disorders: Thrombocytopenia, Leukopenia

Cardiac Disorders: Tachycardia

Gastrointestinal Disorders: Stomatitis, Dry Mouth, Dyspepsia, Upper Abdominal Pain, Abdominal Distension, Dysphagia, Gingival Pain, Stomach Discomfort, Gastroesophageal Reflux Disease, Glossodynia, Mouth Ulceration

General Disorders and Administration Site Conditions: Pyrexia, Application Site Pain, Application Site Ulcer, Chest Pain, Chills, Application Site Irritation, Edema, Mucosal Inflammation, Pain

Hepatobiliary Disorders: Jaundice

Infections and Infestations: Oral Candidiasis, Urinary Tract Infection, Cellulitis, Nasopharyngitis, Sinusitis, Upper Respiratory Tract

Infection, Influenza, Tooth Abscess Injury, Poisoning and Procedural Complications: Fall, Spinal Compression Fracture

Investigations: Decreased Hemoglobin, Increased Blood Glucose, Decreased Hematocrit, Decreased Platelet Count

Metabolism and Nutrition Disorders: Decreased Appetite, Hypoalbuminemia, Hypercalcemia, Hypomagnesemia, Hyponatremia, Reduced Oral Intake

Musculoskeletal and Connective Tissue Disorders: Pain in Extremity, Myalgia, Chest Wall Pain, Muscle Spasms, Neck Pain, Shoulder Pain

Nervous System Disorders: Hypoesthesia, Dysgeusia, Lethargy, Peripheral Neuropathy, Paresthesia, Balance Disorder, Migraine, Neuropathy

Psychiatric Disorders: Anxiety, Disorientation, Euphoric Mood, Hallucination, Nervousness

Renal and Urinary Disorders: Renal Failure

Respiratory, Thoracic and Mediastinal Disorders: Pharyngolaryngeal Pain, Exertional Dyspnea, Pleural Effusion, Decreased Breathing Sounds, Wheezing

Skin and Subcutaneous Tissue Disorders: Pruritus, Rash, Hyperhidrosis, Cold Sweat

Vascular Disorders: Hypertension, Hypotension, Pallor, Deep Vein Thrombosis

Postmarketing Experience

The following adverse reactions have been identified during post approval use of fentanyl. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Nervous System Disorders
  • Serotonin syndrome: Cases of serotonin syndrome, a potentially life-threatening condition, have been reported during concomitant use of opioids with serotonergic drugs.
Endocrine Disorders
  • Adrenal insufficiency: Cases of adrenal insufficiency have been reported with opioid use, more often following greater than one month of use.
  • Androgen deficiency: Cases of androgen deficiency have occurred with chronic use of opioids [see CLINICAL PHARMACOLOGY].
Immune System Disorders
  • Anaphylaxis: Anaphylaxis has been reported with ingredients contained in FENTORA.
  • General Disorders and Administration Site Conditions: Drug withdrawal syndrome


Table 4 includes clinically significant drug interactions with FENTORA.

Table 4: Clinically Significant Drug Interactions with FENTORA

Inhibitors of CYP3A4
Clinical Impact: The concomitant use of FENTORA and CYP3A4 inhibitors can increase the plasma concentration of fentanyl, resulting in increased or prolonged opioid effects, particularly when an inhibitor is added after a stable dose of FENTORA is achieved [see WARNINGS AND PRECAUTIONS].
After stopping a CYP3A4 inhibitor, as the effects of the inhibitor decline, the fentanyl plasma concentration will decrease [seeCLINICAL PHARMACOLOGY], resulting in decreased opioid efficacy or a withdrawal syndrome in patients who had developed physical dependence to fentanyl.
Intervention: If concomitant use is necessary, consider dosage reduction of FENTORA until stable drug effects are achieved. Monitor patients for respiratory depression and sedation at frequent intervals. If a CYP3A4 inhibitor is discontinued, consider increasing the FENTORA dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.
Examples: Macrolide antibiotics (e.g., erythromycin), azole-antifungal agents (e.g., ketoconazole), protease inhibitors (e.g., ritonavir), grapefruit juice
CYP3A4 Inducers
Clinical Impact: The concomitant use of FENTORA and CYP3A4 inducers can decrease the plasma concentration of fentanyl [see CLINICAL PHARMACOLOGY], resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence to fentanyl [see WARNINGS AND PRECAUTIONS].
After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase [see CLINICAL PHARMACOLOGY], which could increase or prolong both the therapeutic effects and adverse reactions, and may cause serious respiratory depression.
Intervention: If concomitant use is necessary, consider increasing the FENTORA dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal. If a CYP3A4 inducer is discontinued, consider FENTORA dosage reduction and monitor for signs of respiratory depression.
Examples: Rifampin, carbamazepine, phenytoin
Benzodiazepines and Other Central Nervous System (CNS) Depressants
Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants including alcohol, increases the risk of respiratory depression, profound sedation, coma, and death.
Intervention: Reserve concomitant prescribing of these drugs for use in patients for whom alternative treatment options are inadequate. Limit dosages and durations to the minimum required. Follow patients closely for signs of respiratory depression and sedation. If concomitant use is warranted, consider prescribing naloxone for the emergency treatment of opioid overdose [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS].
Examples: Benzodiazepines and other sedatives/hypnotics, anxiolytics, tranquilizers, muscle relaxants, general anesthetics, antipsychotics, other opioids, alcohol.
Serotonergic Drugs
Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome [see WARNINGS AND PRECAUTIONS].
Intervention: If concomitant use is warranted, carefully observe the patient, particularly during treatment initiation and dose adjustment. Discontinue FENTORA if serotonin syndrome is suspected.
Examples: Selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that affect the serotonin neurotransmitter system (e.g., mirtazapine, trazodone, tramadol), certain muscle relaxants (i.e., cyclobenzaprine, metaxalone), monoamine oxidase (MAO) inhibitors (those intended to treat psychiatric disorders and also others, such as linezolid and intravenous methylene blue).
Monoamine Oxidase Inhibitors (MAOIs)
Clinical Impact: MAOI interactions with opioids may manifest as serotonin syndrome [see WARNINGS AND PRECAUTIONS] or opioid toxicity (e.g., respiratory depression, coma) [see WARNINGS AND PRECAUTIONS].
Intervention: The use of FENTORA is not recommended for patients taking MAOIs or within 14 days of stopping such treatment.
Examples: Phenelzine, tranylcypromine, linezolid
Mixed Agonist/Antagonist and Partial Agonist Opioid Analgesics
Clinical Impact: May reduce the analgesic effect of FENTORA and/or precipitate withdrawal symptoms.
Intervention: Avoid concomitant use.
Examples: Butorphanol, nalbuphine, pentazocine, buprenorphrine
Muscle Relaxants
Clinical Impact: Fentanyl may enhance the neuromuscular blocking action of skeletal muscle relaxants and produce an increased degree of respiratory depression.
Intervention: Monitor patients for signs of respiratory depression that may be greater than otherwise expected and decrease the dosage of FENTORA and/or the muscle relaxant as necessary. Due to the risk of respiratory depression with concomitant use of skeletal muscle relaxants and opioids, consider prescribing naloxone for the emergency treatment of opioid overdose [see DOSAGE AND ADMINISTRATION, WARNINGS AND PRECAUTIONS].
Examples: cyclobenzaprine, metaxalone
Clinical Impact: Opioids can reduce the efficacy of diuretics by inducing the release of antidiuretic hormone.
Intervention: Monitor patients for signs of diminished diuresis and/or effects on blood pressure and increase the dosage of the diuretic as needed.
Anticholinergic Drugs
Clinical Impact: The concomitant use of anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus.
Intervention: Monitor patients for signs of urinary retention or reduced gastric motility when FENTORA is used concomitantly with anticholinergic drugs.

Drug Abuse And Dependence

Controlled Substance

FENTORA contains fentanyl, a Schedule II controlled substance.


FENTORA contains fentanyl, a substance with high potential for abuse similar to other opioids including hydrocodone, hydromorphone, methadone, morphine, oxycodone, oxymorphone, and tapentadol. FENTORA can be abused and is subject to misuse, addiction, and criminal diversion [see WARNINGS AND PRECAUTIONS].

All patients treated with opioids require careful monitoring for signs of abuse and addiction, since use of opioid analgesic products carries the risk of addiction even under appropriate medical use.

Prescription drug abuse is the intentional non-therapeutic use of a prescription drug, even once, for its rewarding psychological or physiological effects.

Drug addiction is a cluster of behavioral, cognitive, and physiological phenomena that develop after repeated substance use and includes: a strong desire to take the drug, difficulties in controlling its use, persisting in its use despite harmful consequences, a higher priority given to drug use than to other activities and obligations, increased tolerance, and sometimes physical withdrawal.

“Drug-seeking” behavior is very common in persons with substance use disorders. Drug-seeking tactics include emergency calls or visits near the end of office hours, refusal to undergo appropriate examination, testing, or referral, repeated “loss” of prescriptions, tampering with prescriptions, and reluctance to provide prior medical records or contact information for other treating health care provider(s). “Doctor shopping” (visiting multiple prescribers to obtain additional prescriptions) is common among drug abusers and people suffering from untreated addiction. Preoccupation with achieving adequate pain relief can be appropriate behavior in a patient with poor pain control.

Abuse and addiction are separate and distinct from physical dependence and tolerance [see Drug Abuse And Dependence]. Health care providers should be aware that addiction may not be accompanied by concurrent tolerance and symptoms of physical dependence in all addicts. In addition, abuse of opioids can occur in the absence of true addiction.

FENTORA, like other opioids, can be diverted for non-medical use into illicit channels of distribution. Careful record-keeping of prescribing information, including quantity, frequency, and renewal requests, as required by state and federal law, is strongly advised.

Proper assessment of the patient, proper prescribing practices, periodic re-evaluation of therapy, and proper dispensing and storage are appropriate measures that help to limit abuse of opioid drugs.

Risks Specific To The Abuse Of FENTORA

FENTORA is for oral transmucosal use only. Abuse of FENTORA poses a risk of overdose and death. This risk is increased with concurrent abuse of FENTORA with alcohol and other central nervous system depressants.


Both tolerance and physical dependence can develop during chronic opioid therapy. Tolerance is the need for increasing doses of opioids to maintain a defined effect such as analgesia (in the absence of disease progression or other external factors). Tolerance may occur to both the desired and undesired effects of drugs, and may develop at different rates for different effects.

Physical dependence results in withdrawal symptoms after abrupt discontinuation or a significant dosage reduction of a drug. Withdrawal also may be precipitated through the administration of drugs with opioid antagonist activity (e.g., naloxone, nalmefene) mixed agonist/antagonist analgesics (e.g., pentazocine, butorphanol, nalbuphine), or partial agonists (e.g., buprenorphine). Physical dependence may not occur to a clinically significant degree until after several days to weeks of continued opioid usage.

Infants born to mothers physically dependent on opioids will also be physically dependent and may exhibit respiratory difficulties and withdrawal signs [see Use In Specific Populations].

Read the entire FDA prescribing information for Fentora (Fentanyl Buccal Tablet)

© Fentora Patient Information is supplied by Cerner Multum, Inc. and Fentora Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

Health Solutions From Our Sponsors