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Fentora Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Fentora (fentanyl citrate) is used to treat "breakthrough" cancer pain that is not controlled by other medicines. It is a narcotic (opioid) pain medicine. This medication is available in generic form. Common side effects include nausea, vomiting, constipation, lightheadedness, dizziness, drowsiness, or headache. Pain, sores, or irritation in the mouth (where the medication has been applied) may also occur. Some side effects may decrease after using this medication for a while.

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. 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. 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 breast-feeding. Withdrawal symptoms may occur if you suddenly stop using this medication.

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.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Fentora in Detail - Patient Information: Side Effects

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

Stop using fentanyl and call your doctor at once if you have a serious side effect such as:

  • weak or shallow breathing;
  • pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating; or
  • feeling very thirsty or hot, being unable to urinate, heavy sweating, or hot and dry skin.

Less serious side effects may include:

  • nausea, vomiting, constipation;
  • dizziness, drowsiness;
  • headache;
  • feeling weak or tired;
  • swelling in your hands or feet; or
  • pain or mouth sores where the medicine was placed.

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) »

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Fentora Overview - Patient Information: Side Effects

SIDE EFFECTS: Nausea, vomiting, constipation, lightheadedness, dizziness, drowsiness, or headache may occur. Pain, sores, or irritation in the mouth (where the medication has been applied) may also occur. Some of these side effects may decrease after you have been using this medication for a while. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To prevent constipation, eat a diet adequate in fiber, drink plenty of water, and exercise. Ask your pharmacist for help in selecting a laxative (such as a stimulant type with stool softener).

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: mental/mood changes (such as agitation, confusion, hallucinations), severe stomach/abdominal pain, difficulty urinating.

Get medical help right away if any of these rare but serious side effects occur: fainting, seizure, slow/shallow breathing, unusual drowsiness/difficulty waking up.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Fentora (Fentanyl Buccal Tablet)»

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Fentora FDA Prescribing Information: Side Effects
(Adverse Reactions)


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 most commonly observed adverse events seen with FENTORA are typical of opioid side effects. Opioid side effects should be expected and managed accordingly.

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.

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

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


Fentora - User Reviews

Fentora User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Fentora sorted by most helpful. Patient Discussions FAQs

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