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Fentanyl Side Effects


Fentanyl is a narcotic analgesic, which has a short duration of action and rapid onset. Fentanyl is manufactured in the brand names of Matrifen, Lazanda, Abstral, Instanyl, Onsolis, Haldid, Fetora, Duragesic, Durogesic and Actig. It is an agonist of the opioid receptors, which significantly limits the transmission of pain impulses by decreasing the calcium electrolyte levels inside the cells.

fentanyl side effects

Uses of Fentanyl

Fentanyl was historically used for the treatment of breakthrough pain. It is given in patients before surgical procedures in conjunction to benzopdiazepines as an anesthetic. The vast uses of fentanyl in pain relief made way for the manufacture of fentanyl citrate, which is widely used as a general anesthetic agent. There were additional fentanyl analogues, which have been developed. Fentanyl also became a palliative treatment in the form of Duragesic patch, Fentora buccal tablets and Actig lollipop. Historically, fentanyl was also used to incapacitate and to kill in military applications. Because of its effects, it has also been used as a recreational drug, causing fatalities of several people. Today, the approved uses of Fentanyl include:

  • Anesthetics for surgical procedures such as in epidural or intrathecal routes
  • Analgesics in patients in intensive care units needing pain relief
  • Sedation for cardiac catheterization, endoscopy and oral surgery in conjunction with midazolam, a benzodiazepine drug
  • Management of chronic pains such as the presence of cancer pain
  • Adjunct anesthetic for root canal treatment and pulpectomy
  • Pain relief for patients with renal failure
  • Pain relief for patients that cannot tolerate other forms of opioids such as morphine

Fentanyl Side effects

The side effects of fentanyl are vast and it may affect all the organ systems in the body. Careful use of the drug will usually not result to these fentanyl side-effects. Fentanyl side effects include:

1. Nervous system Fentanyl Side effects

Mental Depression

This fentanyl side effect is rooted on the inhibition of nerve impulses in the brain. Patients may suffer from delirium, stupor, dysphoria and somnolence similar to carbamazepine side effects.

Myoclonic Seizures

This type of seizure has also been observed in patients using transdermal therapy. These seizures may have occurred due to fentanyl induced rigidity.


A case of hemiplegic migraine has also been documented with the use of fentanyl for sedation.

Drug abuse

Fentanyl has potential for drug abuse because of development of drug dependence.


Stopping fentanyl may lead to withdrawal syndrome because of possible drug dependence.

2. Cardiovascular Fentanyl Side effects


Fentanyl may also cause hypotension because of possible vasodilating effects. Safety should be ensured to prevent falls.


Fentanyl may aldo cause slowing of the heart rate due to CNS depression and possibly slowing down of the action potentials in the heart as well.

3. Gastrointestinal Fentanyl Side effects

Nausea and Vomiting

The opioid receptors in the gastrointestinal system may also be affected leading to nausea and vomiting because of slowed peristalsis of the GIT.


Slowed peristalsis may also lead to constipation. Increased fiber and fluid intake may reduce this fentanyl side effect.

Choledocoduodenal sphincter spasm

Rare occurrence of spasm in the sphincter of the common bile duct in the duodenum has been documented. This may be due to fentanyl induced rigidity.

4. Respiratory Fentanyl Side effects

Respiratory Depression

The inhibition of nerve impulses in the central nervous system also slows the action of the respiratory center of the brain, which is located on the brain stem. Probably, this is the most serious fentanyl side effect because it can bring about respiratory failure leading to death. Observe for shortness of breath, decreased rate of breathing and shallow respirations.

5. Genitourinary Fentanyl Side effects

Urinary retention

The urinary system also has opiate receptors leading to urinary retention when fentanyl binds with its receptors in the bladder.

6. Dermatologic Fentanyl Side effects

Pruritus and rashes

Rashes and pruritus have been documented due to mild hypersensitivity reactions especially in the use of transdermal patches.

7. Hematologic Fentanyl Side effects


Destruction of RBCs was seen in patients receiving large volumes of hypotonic fentanyl via the intravenous route. In order to prevent this, injections should be in slower rates or use of isotonic solutions.

8. Metabolic Fentanyl Side effects


Syndrome of inappropriate anti-diuretic hormone involves the presence of high amounts of anti-diuretic hormone, leading to water retention and edema. This fentanyl side effect is rarely developing.

9. Immunologic Fentanyl Side effects

Increased Killer cells and CD 16+ lymphocytes

The levels of these white blood cells have been increased in some patients receiving fentanyl although the exact mechanism is still unclear.

Since fentanyl side effects are vast, physicians prescribing it usually use caution in dosing because over dosage increases the risk for life-threatening fentanyl side effects such as respiratory depression. Despite thesefentanyl side effects, it is still beneficial for patients requiring pain relief and bedsides; it is considered the safest opioid analgesic, despite its fentanyl side-effects.

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