Fentanyl is used to treat severe pain in cancer patients. It is used for breakthrough cancer pain, which are flares of pain that “break through” after a routine pain medicine has been used. Fentanyl belongs to the group of medicines called narcotic analgesics. It is only used in patients who are already taking narcotic analgesics.

Fentanyl acts in the central nervous system (CNS) to relieve pain. Some of its side effects are also caused by actions in the CNS. When a narcotic is used for a long time, it may become habit-forming or cause mental or physical dependence. However, people who have continuous pain should not let the fear of dependence keep them from using narcotics to relieve pain. Mental dependence (addiction) is not likely to occur when narcotics are used for this purpose. Physical dependence may lead to withdrawal side effects if treatment is stopped suddenly. Withdrawal side effects can usually be prevented by gradually reducing the dose over a period of time before the medicine is stopped completely. Talk to your doctor about the benefits of this medicine and how to prevent withdrawal side effects.

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  • fentanyl
  • Severity: Major
    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
    decreased urine
    difficult or labored breathing
    dry mouth
    fever or chills
    increased thirst
    irregular heartbeat
    loss of appetite
    lower back or side pain
    mood changes
    muscle pain or cramps
    nausea or vomiting
    numbness or tingling in the hands, feet, or lips
    painful or difficult urination
    pale skin
    pounding in the ears
    rapid breathing
    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
    muscle twitching or jerking
    pounding in the ears
    rhythmic movement of the muscles
    seeing, hearing, or feeling things that are not there
    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
    Severity: Minor
    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
    difficulty having a bowel movement (stool)
    difficulty with moving
    feeling sad or empty
    lack or loss of strength
    loss of interest or pleasure
    muscle stiffness
    pain in the joints
    sleepiness or unusual drowsiness
    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
    sensation of spinning
    Incidence not known:
    Tooth pain
    trouble with gums
    trouble with teeth
    Side Effects: Post Treatment
    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:

    speech disorder
    stomach cramps
  • (fentanyl citrate) lozenge