Overview
Fentanyl is a potent synthetic opioid analgesic with rapid onset and short duration of action. It is approximately 50-100 times more potent than morphine and is used for management of severe pain, typically in patients who are opioid-tolerant. Fentanyl works by binding to mu-opioid receptors in the central nervous system, altering pain perception and emotional response to pain.
Mechanism of Action
Fentanyl is a pure mu-opioid receptor agonist. It binds selectively to opioid receptors in the brain, spinal cord, and peripheral tissues, leading to decreased pain perception, sedation, and respiratory depression. Its high lipid solubility allows rapid penetration of the blood-brain barrier.
Indications
- Management of severe chronic pain in opioid-tolerant patients
- Breakthrough cancer pain in opioid-tolerant cancer patients
- Anesthesia adjunct
- Postoperative pain management
- Chronic pain management when other opioids are inadequate
Dosage
Dosage must be individualized based on pain severity, patient response, and prior opioid exposure. Transdermal patches (Durogesic): Initial dose based on prior opioid use, typically applied every 72 hours. Buccal tablets/lozenges: For breakthrough pain, starting dose 100-200 mcg. All routes require careful titration and monitoring.
Contraindications
- Hypersensitivity to fentanyl or components
- Acute or severe bronchial asthma
- Gastrointestinal obstruction
- Respiratory depression
- Non-opioid tolerant patients
- Management of acute or postoperative pain (except specific formulations)
- Concurrent MAOI use or within 14 days of discontinuation
Side Effects
- Respiratory depression
- Sedation
- Nausea and vomiting
- Constipation
- Hypotension
- Bradycardia
- Muscle rigidity
- Pruritus
- Sweating
- Dizziness
- Confusion
- Headache
- Dry mouth
- Urinary retention
- Withdrawal symptoms with abrupt discontinuation
Interactions
- CNS depressants (alcohol, benzodiazepines, other opioids): Increased respiratory depression
- MAO inhibitors: Potentially fatal reactions
- Serotonergic drugs: Risk of serotonin syndrome
- CYP3A4 inhibitors (ketoconazole, ritonavir): Increased fentanyl levels
- CYP3A4 inducers (rifampin, carbamazepine): Decreased fentanyl efficacy
- Muscle relaxants: Enhanced neuromuscular blocking action