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Fentanyl (Sublimaze, Duragesic, Actiq)

Opioid analgesic (high-alert; full mu-receptor agonist)

Mechanism of action

Highly potent synthetic mu-opioid agonist (~100× morphine) with rapid onset and short duration when given IV. Lipophilic and high-extraction — accumulates in fat with prolonged infusion ("context-sensitive half-time" rises). Used for procedural sedation, ICU sedation, severe acute pain, anesthesia, and chronic pain in opioid-tolerant patients (transdermal patch).

Adverse effects

Life-threatening / NCLEX-tested

  • Respiratory depression — life-threatening; faster onset than morphine
  • Chest wall rigidity ("wooden chest") with rapid IV bolus — can prevent ventilation; treat with neuromuscular blockade and naloxone
  • Severe bradycardia and hypotension
  • Severe sedation and coma
  • Serotonin syndrome with serotonergic drugs
  • Tolerance, physical dependence, opioid use disorder
  • Iatrogenic overdose with patches (especially in opioid-naive patients — should NEVER be used in opioid-naive patients)

Side effects

Common — what to teach

  • Drowsiness, sedation
  • Nausea, vomiting
  • Constipation
  • Pruritus
  • Mild bradycardia
  • Miosis

Food & drug interactions

Other CNS depressants (benzodiazepines, alcohol, gabapentinoids) compound respiratory depression. Strong CYP3A4 inhibitors (clarithromycin, ritonavir, ketoconazole) raise fentanyl levels — life-threatening with patches. Strong CYP3A4 inducers lower levels (rifampin, carbamazepine). Heat (heating pads, fever, hot baths) accelerates patch absorption — avoid. Naloxone reverses (often need repeat doses due to fentanyl's pharmacokinetics).

Nursing implications

Assessment, monitoring, patient teaching

  • Patches: ONLY for opioid-tolerant chronic pain patients; NEVER initiate in opioid-naive; apply to clean dry hairless skin; rotate sites; avoid heat exposure; replace every 72 hours; remove old patch before applying new
  • Two-nurse verification for IV doses and high-alert administration
  • Continuous monitoring (RR, SpO2, capnography preferred) during procedural sedation and infusions
  • Have naloxone immediately available; expect to repeat doses for fentanyl reversal because of long half-life
  • Teach patients and families NOT to cut patches, NOT to share, NOT to use heating pads on patch sites; dispose of used patches by folding sticky-side together and flushing per FDA guidance for highly hazardous drugs
  • Counsel rigorously against combining with benzodiazepines or alcohol — fentanyl is the leading driver of overdose deaths
  • Watch for chest rigidity in OR/procedural settings — treat with NMB + naloxone if it impairs ventilation

When to hold / contraindications

  • RR < 12 (or institutional threshold)
  • Excessive sedation
  • Hemodynamic instability with severe hypotension or bradycardia
  • Patch in an opioid-naive patient — remove and reassess analgesic plan
  • Active fever or heat exposure with a transdermal patch
  • Severe respiratory disease without escalating monitoring

Memory anchor

Fentanyl is ~100× morphine. Patches are NOT for opioid-naive patients. Heat raises absorption. Naloxone reverses but needs repeat dosing. "Wooden chest" with rapid IV push.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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