Fentora Side Effects

Fentora is the brand name preparation of buccal fentanyl available in a tablet form. This medication is also known as transmucosal immediate release fentanyl. Physicians prescribe Fentora for the treatment of breakthrough pain in cancer patients who are already tolerant to opioids. Fentora must never be used in patients who are not already tolerant to other opioids, such as morphine or codeine; life-threatening breathing problems or death could occur at any dose in individuals who are not tolerant to opioids.

This drug, like all medicine, has the potential to cause side effects. Many people experience no, or minor, side effects from taking this medication. Most side effects are not serious and disappear after a few days. A few side effects are serious and require the attention of a medical professional.

Potential for abuse, physical dependence or addiction are possible side effects from taking this drug. The U.S. Drug Enforcement Agency, or DEA, classifies substances according to the potential for abuse. The DEA has classified fentanyl as a Schedule II narcotic, which means it carries a high potential for abuse and mental or physical dependence.

Because Fentora poses a special risk for abuse, misuse, addiction and overdose, this medication is only available through a restricted program called TIRF REMS, or Transmucosal Immediate Release Fentanyl (TIRF) Risk Evaluation and Mitigation Strategy (REMS) Access Program. Under the guidelines of this program, outpatients and their associated physicians, pharmacies, clinics and distributors must enroll in TIRF REMS. Physicians enrolled in TIRF REMS must review the prescriber information sheets, pharmacies must agree to comply with REMS requirements, wholesalers agree to distribute Fentora only to authorized pharmacies. Outpatients must understand the risks and benefits of Fentora and sign a patient-prescriber agreement. Inpatients and the healthcare providers who treat them are not required to enroll in TIRF REMS.

Physical dependence means the individual will suffer withdrawal symptoms after the level of opioid drops in his system, because either he has stopped taking opioids or he has taken a medication to reduce the amount of this drug in his system rapidly. Withdrawal symptoms include:

  • Abdominal Cramps
  • Agitation
  • Anxiety
  • Blurred Vision
  • Insomnia
  • Restlessness
  • Sweating
  • Tremor
  • Vomiting

The adverse reactions to this drug are typical of any opioids. These side effects usually decrease in intensity or stop altogether with continued use at proper doses. The most serious side effect is respiratory problems potentially leading to stopped breathing, circulatory depression, dangerously low blood pressure and shock. Physicians should expect side effects and treat patients accordingly.

Respiratory depression, a significant side effect of Fentora and other opioids, is a condition where the lungs do not adequately exchange oxygen and carbon dioxide, characterized by slow or shallow breathing.

The most common side effects associated with this medication are not serious and disappear after taking this drug for a few days. Continue taking this medication but contact the prescribing physician if the following side effects become intolerable or if they do not go away on their own:

  • Constipation
  • Dizziness
  • Drowsiness
  • Dry Mouth
  • Fatigue
  • Headache
  • Mild Pain or Irritation at the Site Where the Tablet is Used
  • Nausea or Vomiting
  • Numbness or Tingling
  • Weakness

Some side effects are serious, requiring immediate medical attention. Stop taking this medication immediately and contact a doctor if you experience serious side effects, including:

  • Blurred Vision or Other Vision Problems
  • Chest Pain
  • Confusion
  • Fainting
  • Fast, Slow or Irregular Heartbeat
  • Hallucinations
  • Mood or Mental Changes
  • Mouth Sores, Ulcers, Bleeding, or Inflammation
  • Seizures
  • Severe Drowsiness
  • Severe Dry Eyes, Mouth, or Skin
  • Severe or Persistent Dizziness or Headache
  • Severe or Persistent Stomach Pain
  • Shortness of Breath
  • Slowed or Shallow Breathing
  • Trouble Urinating
  • Unusual or Severe Weakness or Fatigue.

By body system

Blood and Lymphatic System

Fentora may lower platelet and white blood cell count in a way that interfere with the body's ability to make blood clots and fight off infectious diseases.


Fentora may cause tachycardia, or a rapid heartbeat. This medication may also cause high blood pressure, low blood pressure or pale skin. This opioid may also cause deep vein thrombosis, or a blood clot in a vein deep inside the body, most commonly in the lower leg.


Fentora may cause a dry mouth, a burning sensation or ulcers in the mouth, gum pain or stomatitis, which is an inflammation of any structure in the mouth including gums, cheeks, tongue, lips and throat. It may also cause indigestion, heartburn, stomach pain or bloating. This medicine may also cause dysphagia, or difficulty swallowing.

General Side Effects

In clinical trials, about 10 percent of patients exposed to Fentora reported reactions at the application site. Fentora may cause warmth, pain or ulcers at the application site. It may also cause chest pain, chills, fever and swelling.


Fentora may cause jaundice, or a yellowing of the skin and eyes.

Infections and Infestations

This medication may cause the mouth infection oral candidiasis, commonly known as thrush. Fentora may also increase the risk for urinary tract infections, influenza, sinus infections and upper respiratory tract infections. This drug is associated with an increased incidence of tooth abscess and the skin infection, cellulitis. Patients are at increased risk for nasopharyngitis, otherwise known as the common cold.

Injury, Poisoning and Procedural Complications

Taking Fentora increases the risk for injuries due to falling.


Fentora may result in anemia, or decreased hemoglobin or hematocrit. This opioid might also increase blood sugar levels. It may also decrease platelet count, increasing the risk for bleeding disorders.

Metabolism and Nutrition

This medication may decrease appetite and result in reduced oral intake. The individual may consequently lose weight or suffer from malnutrition. Fentora is associated with hypoalbuminemia, or low levels of albumin in the blood; albumin is an important protein that makes up about 60 percent of the plasma in the human body. Fentora may also be associated with other metabolic side effects, such as high calcium, low magnesium and low sodium in the bloodstream.

Musculoskeletal and Connective Tissue

Fentora is associated with musculoskeletal and connective tissue disorder side effects such as pain in the arms and legs, muscle pain or spasms, chest wall pain or pain the shoulder or neck.

Nervous System

This opioid pain reliever may cause side effects in the nervous system. These side effects include hypoesthesia, which is a reduced sense of touch, or dysgeusia, which is an abnormal or distorted sense of taste. This medication may cause paresthesia, or an abnormal tingling, numbness or burning sensation in the skin. Other nervous system side effects associated with Fentora are lethargy, migraine headaches and balance disorders. Individuals who take Fentora may experience peripheral neuropathy, which is damage to the peripheral nervous system, the vast communications network that transmits information between the brain and spinal cord and the rest of the body. This medication may be associated with other types of neuropathy, or nerve damage.


Fentora is associated with side effects that produce psychiatric disorders, such as anxiety, disorientation, nervousness or hallucinations. It may also cause euphoria.

Renal and Urinary

Taking the opioid Fentora may result in renal failure in some patients.


Fentora may cause side effects involving the respiratory system. Side effects include throat pain, shortness of breath during exercise, fluid in the lung, abnormal breath sounds or wheezing.

Skin and Subcutaneous Tissue

This medication may cause itching, rash, cold sweats or excessive sweating.