Fentanyl Side Effects

Not all side effects for fentanyl may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to fentanyl: film, lozenge/troche, spray, tablet

In addition to its needed effects, some unwanted effects may be caused by fentanyl. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking fentanyl:

More common
  • Black, tarry stools
  • blurred vision
  • chest pain
  • confusion
  • convulsions
  • cough
  • decreased urine
  • difficult or labored breathing
  • dizziness
  • dry mouth
  • fainting
  • fever or chills
  • increased thirst
  • irregular heartbeat
  • lightheadedness
  • loss of appetite
  • lower back or side pain
  • mood changes
  • muscle pain or cramps
  • nausea or vomiting
  • nervousness
  • numbness or tingling in the hands, feet, or lips
  • painful or difficult urination
  • pale skin
  • pounding in the ears
  • rapid breathing
  • sneezing
  • sore throat
  • sunken eyes
  • swelling of the hands, ankles, feet, or lower legs
  • tightness in the chest
  • troubled breathing with exertion
  • ulcers, sores, or white spots in the mouth
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • wrinkled skin
Less common
  • Abdominal or stomach pain
  • change in walking and balance
  • clumsiness or unsteadiness
  • decreased awareness or responsiveness
  • decreased frequency of urination
  • headache
  • muscle twitching or jerking
  • pounding in the ears
  • rhythmic movement of the muscles
  • seeing, hearing, or feeling things that are not there
  • seizures
  • severe constipation
  • severe sleepiness
  • shakiness in the legs, arms, hands, or feet
  • slow or fast heartbeat
  • thinking abnormalities
  • trembling or shaking of the hands or feet

If any of the following symptoms of overdose occur while taking fentanyl, get emergency help immediately:

Symptoms of overdose
  • Extremely shallow or slow breathing

Some of the side effects that can occur with fentanyl may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Back pain
  • diarrhea
  • difficulty having a bowel movement (stool)
  • difficulty with moving
  • discouragement
  • feeling sad or empty
  • irritability
  • lack or loss of strength
  • loss of interest or pleasure
  • muscle stiffness
  • pain in the joints
  • sleepiness or unusual drowsiness
  • tiredness
  • trouble concentrating
  • trouble sleeping
  • weight loss
Less common
  • Changes in vision
  • excessive muscle tone
  • feeling of constant movement of self or surroundings
  • feeling of warmth or heat
  • flushing or redness of the skin, especially on the face and neck
  • irritation, pain, or sores at the site of application
  • itching skin
  • muscle tension or tightness
  • rash
  • sensation of spinning
  • sweating
Incidence not known
  • Tooth pain
  • trouble with gums
  • trouble with teeth

After you stop taking this drug, it is possible that you may still experience side effects that need medical attention. If you notice any of the following side effects check with your doctor immediately:

  • Restlessness
  • speech disorder
  • stomach cramps
  • weakness

For Healthcare Professionals

Applies to fentanyl: buccal film, buccal tablet, compounding powder, injectable solution, nasal spray, oral lozenge, oral transmucosal lozenge, sublingual spray, sublingual tablet, transdermal device, transdermal film extended release

Nervous system

Very common (10% or more): Somnolence, dizziness
Common (1% to 10%): Sedation, pyrexia, fatigue, lethargy, tremor, headache, chills, irritability, malaise, confusion, abnormal thinking, anxiety, dysphoria
Uncommon (0.1% to 1%): Hyperesthesia
Very rare (less than 0.01%): Severe hemiplegic migraine
Frequency not reported: Slurred speech
Postmarketing reports: Loss of consciousness, vertigo, coma, shock, convulsion

Cases of seizures have occasionally been reported, but some investigators have suggested that the seizure-like events reported may have been episodes of fentanyl induced-rigidity.

Cardiovascular

Common (1% to 10%): Tachycardia
Uncommon (0.1% to 1%): Sinus tachycardia, chest pain, hypertension, hypotension, palpitations
Rare (less than 0.1%): Arrhythmias, cardiac arrest
Postmarketing reports: Circulatory depression

One report has suggested that epidural fentanyl may mask the pain of myocardial ischemia in patients treated with fentanyl for other reasons. Another report has suggested that QTc interval prolongation may occur in some patients receiving the related narcotic sufentanil. Another report has implicated fentanyl as a potential cause of pulsus alternans in a patient with aortic stenosis and congestive heart failure.

Nevertheless, fentanyl has been advocated by some as a satisfactory agent for coronary artery surgery.

Gastrointestinal

Very common (10% or more): Nausea (18%), vomiting (10%), constipation
Common (1% to 10%): Dry mouth, abdominal distension, gastritis, dysphagia, dyspepsia, gastroesophageal reflux disease, ascites, hematemesis, taste perversion, abdominal pain, dehydration, anorexia, cachexia, vomiting, dry mouth, mouth ulcers/stomatitis, tongue edema
Uncommon (0.1% to 1%): Abdomen enlarged, flatulence
Rare (less than 0.1%): Choledochoduodenal sphincter spasm
Postmarketing reports: Ileus, dental caries, tooth loss, gingival recession, gingivitis, gingival bleeding, lip edema, pharyngeal edema, gum bleeding, ulcer

Genitourinary

Uncommon (0.1% to 1%): Urinary retention
Very rare (less than 0.01%): Priapism

Dermatologic

Common (1% to 10%): Application site irritation, pruritus
Uncommon (0.1% to 1%): Hyperhidrosis, rash
Rare (less than 0.1%): Systemic rashes

Hypersensitivity

Rare (less than 0.1%): Anaphylaxis

Hematologic

Common (1% to 10%): Anemia, neutropenia, lymphadenopathy, thrombocytopenia, leukopenia, aspartate aminotransferase increased, blood alkaline phosphatase increased, blood glucose increased, blood lactate increased, hypoalbuminemia, vasodilation

The hemolysis observed may have been related to rapid injection of large volumes of hypotonic fentanyl solution. The authors therefore recommend slower injection rates and/or mixture in isotonic fluid.

Immunologic

Uncommon (0.1% to 1%): Oral candidiasis, cellulitis, pneumonia, urinary tract infection, oral herpes, gastroenteritis, laryngitis
Very rare (less than 0.01%): Recurrent herpes simplex infection following epidural administration

Metabolic

Common (1% to 10%): Asthenia, peripheral edema, weight decreased, hypokalemia, hyponatremia, hypocalcemia
Very rare (less than 0.01%): Syndrome of inappropriate antidiuretic hormone

Endocrine

Uncommon (0.1% to 1%): Hot flush

Musculoskeletal

Common (1% to 10%): Fall/accidental injury, back pain, arthralgia, joint swelling, muscular weakness, myoclonus, involuntary muscle contractions, muscle rigidity (involving the respiratory musculature including the glottis)
Postmarketing reports: Abnormal gait/incoordination

Ocular

Uncommon (0.1% to 1%): Vision blurred, dry eye
Rare (less than 0.1%): Abnormal vision

Psychiatric

Common (1% to 10%): Depression, confusional state, hallucination, insomnia
Uncommon (0.1% to 1%): Anxiety, agitation, restlessness, agitation, disorientation, abnormal dreams, depersonalization, depression, emotional lability, euphoria, delirium

Respiratory

Common (1% to 10%): Dyspnea, rhinitis, yawning, dyspnea, respiratory distress, apnea, bradypnea, hypoventilation, respiratory depression
Uncommon (0.1% to 1%): Cough, increased bronchial secretion, dysphonia, pharyngolaryngeal pain, wheezing, hypoxia, exertional dyspnea
Very rare (less than 0.01%): Acute noncardiogenic pulmonary edema
Postmarketing reports: Respiratory arrest

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