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Fentanyl is typically used to treat patients with severe pain, or to manage pain after surgery. It is also used for management of severe, chronic or breakthrough pain (sudden pain occurring in spite of other routine pain relieving medications) especially in cancer patients.

How it works

Fentanyl belongs to a class of drugs called opioid analgesics. It acts by inhibiting certain receptors in the brain associated with perception of pain.

Common side effects

Drowsiness, Allergic skin rash, Back pain, Bloody diarrhea, Numbness, Burning sensation, Tingling sensation, Central nervous system depression, Confusion, Dizziness, Dry mouth, Difficulty in urination, Feeling thirsty, Feeling of cold, Hallucination, Headache, Increased sweating, Indigestion, Insomnia, Mood changes, Stomach pain, Tremor, Weakness, Vomiting, Nausea, Loss of appetite


Expert advice

  • Do not consume fentanyl in doses more than that as prescribed by the doctor as it has a potential for addiction.
  • Seek immediate medical attention if you experience difficulty in breathing after administration fentanyl.
  • Avoid exposure to high temperature conditions such sauna bath, hot tub bath, sun bathing as this may lead to increased absorption of fentanyl causing overdose and adverse effects.
  • Do not drive or operate machinery while taking fentanyl as it may cause dizziness. 
  • Consult your doctor before taking  fentanyl if you have breathing problems, low blood pressure, heart, liver, chronic lung or kidney diseases,  brain tumor, head injury, or myasthenia gravis (neuromuscular disease characterized by progressive weakness of  muscles and unusual tiredness).
  • Do not consume this drug if are allergic to fentanyl or any of its ingredients or any other opioid analgesic.
  • Do not consume this drug if you are regularly using opioid medication for management of persistent pain.
  • Patients who are suffering from mild pain should not consume this drug.
  • Inform your doctor if you are or planning to get pregnant or breastfeeding. 

Frequently asked questions


Q. Is fentanyl an opioid/ morphine/ barbiturate?
Fentanyl is an opioid analgesic. It is not morphine or barbiturate.
Q. Is fentanyl addictive/ controlled substance?
Fentanyl is a controlled substance and has got addictive potential. Always follow the doctor’s instruction regarding its use.
Q. Does fentanyl cause constipation/ hypotension?
Fentanyl may cause constipation and hypotension. Please consult your doctor if you experience such side effects.

Content on this page was last updated on 30 September, 2016, by Dr. Varun Gupta (MD Pharmacology)