Bedside Snapshot
  • Ultra-Short-Acting μ-Opioid: Used primarily in anesthesia for finely titratable analgesia and sympathetic blunting
  • Unique Metabolism: Metabolized by non-specific plasma and tissue esterases, making context-sensitive half-time ~3-5 minutes regardless of infusion duration
  • Rapid Onset, Rapid Offset: Provides analgesia within 1 minute; when infusion stops, analgesia disappears within minutes
  • Not for Routine ICU: Risk of abrupt pain/hyperalgesia unless longer-acting opioid in place before stopping
  • Major Risks: Profound respiratory depression, bradycardia, hypotension, chest wall rigidity (especially with rapid bolus), acute opioid withdrawal/hyperalgesia after high-dose or prolonged infusions
  • Organ-Independent: Clearance largely independent of liver and kidney function
Brand & Generic Names
  • Generic Name: Remifentanil hydrochloride
  • Brand Names: Ultiva, generics
Medication Class

Ultra-short-acting synthetic opioid analgesic; μ-opioid receptor agonist

Pharmacology

Mechanism of Action:

  • Selective μ-opioid receptor agonist, similar to fentanyl, acting at receptors in CNS and spinal cord
  • Activation of μ-receptors leads to inhibition of adenylate cyclase, decreased cAMP, enhanced K⁺ efflux, and decreased Ca²⁺ influx → reduced neuronal excitability and neurotransmitter release
  • Produces potent analgesia, sedation, respiratory depression, and blunting of sympathetic responses to noxious stimuli

Pharmacokinetics (IV):

  • Onset: Very rapid, with onset of analgesia typically within 1 minute of IV administration
  • Metabolism: Hydrolyzed by non-specific plasma and tissue esterases into inactive metabolites; process independent of liver and kidney function
  • Elimination half-life: ~3-10 minutes; context-sensitive half-time remains ~3-5 minutes even after prolonged infusions, unlike most other opioids
  • Distribution: Relatively small volume; high clearance; minimal accumulation even with long infusions, though receptor tolerance/hyperalgesia may occur
  • Critical Point: Because of rapid offset, analgesia disappears quickly when infusion stops unless another analgesic is in place
Dosing & Administration

Available Forms:

  • Lyophilized powder vials containing 1 mg, 2 mg, or 5 mg remifentanil for IV reconstitution
  • Common infusion concentrations: 25-50 mcg/mL prepared in normal saline or D5W and delivered via syringe pump or volumetric pump
  • Because of potency and rapid onset, use dedicated lines/pumps and label clearly

Remifentanil Dosing (Adult; Anesthesia-Focused):

Indication / Scenario Loading / Bolus Infusion Rate Notes
Induction of anesthesia (optional bolus) 0.5-1 mcg/kg 0.05-2 mcg/kg/min Bolus over 30-60 s; given with hypnotic (propofol, etomidate, etc.)
Maintenance of anesthesia — 0.05-2 mcg/kg/min Titrate to surgical stimulus and blood pressure/HR
Procedural analgesia (intubated ICU patient) 0-0.5 mcg/kg 0.025-0.2 mcg/kg/min Use with full ventilatory support and close monitoring
Elderly or hemodynamically unstable 0.25-0.5 mcg/kg 0.025-0.1 mcg/kg/min Start low and titrate cautiously due to sensitivity to hypotension/bradycardia
ICU continuous sedation (not routine) — 0.025-0.2 mcg/kg/min Generally avoided for long-term sedation due to withdrawal and hyperalgesia
Renal impairment Standard Standard infusion Clearance largely independent of renal function; still monitor response
Hepatic impairment Standard Standard infusion Metabolism is esterase-based, not hepatic; effects still may be exaggerated in fragile patients
Discontinuation — Stop infusion Expect rapid return of pain; give longer-acting opioid before stopping if ongoing analgesia needed
Transition Required: Always administer longer-acting opioid or multimodal analgesia prior to stopping to avoid sudden severe pain.
Contraindications

Contraindications:

  • Known hypersensitivity to remifentanil, fentanyl analogs, or formulation components
  • Use in non-monitored settings without immediate access to airway management and ventilatory support

Major Precautions:

  • Respiratory depression: Profound respiratory depression and apnea, especially with rapid bolus doses; intubation/ventilation capacity must be immediately available
  • Hemodynamic effects: Bradycardia and hypotension, particularly when combined with other anesthetics or in hypovolemic patients
  • Chest wall rigidity: At high doses or rapid bolus → may require neuromuscular blockade and mechanical ventilation
  • Rapid offset concerns: Can lead to sudden, severe pain and opioid-induced hyperalgesia; transition to longer-acting analgesics essential if pain expected post-op
  • Prolonged infusions: Physical dependence and withdrawal can develop
Adverse Effects

Common:

  • Respiratory depression, hypoventilation, apnea
  • Bradycardia, hypotension
  • Nausea, vomiting
  • Pruritus

Serious:

  • Chest wall rigidity with impaired ventilation
  • Severe hypotension or bradyarrhythmias requiring intervention
  • Cardiorespiratory arrest in absence of adequate monitoring and support
Monitoring

During Infusion:

  • Continuous ECG, blood pressure, and pulse oximetry
  • In ventilated patients: Tidal volumes, ventilator pressures, and ETCO₂
  • Analgesia and sedation levels; plan for alternative analgesics before discontinuation
  • Signs of hyperalgesia or withdrawal with prolonged/high-dose use
Indications / Clinical Uses (OR/ICU Focus)
  • Anesthesia: Analgesia and blunting of hemodynamic responses during induction and maintenance of general anesthesia, often as part of TIVA regimens with propofol
  • Procedural analgesia: In ventilated ICU patients for brief, intensely painful procedures (e.g., bronchoscopy, chest tube insertion) under close monitoring
  • Neuroanesthesia: Cases requiring rapid postoperative neurologic assessment with quick recovery from opioids
  • Organ failure: Situations where hepatic/renal failure makes clearance of other opioids unpredictable
Clinical Pearls
Precise Control: Ideal when you need precise moment-to-moment analgesic control and rapid neurologic assessment afterward (e.g., neuro cases).
Anticipate End of Infusion: Always administer a longer-acting opioid or multimodal analgesia prior to stopping to avoid a wall of pain.
Avoid Rapid Boluses: Prefer small boluses or controlled infusion adjustments to reduce chest wall rigidity and hemodynamic swings.
Critically Ill Patients: Even though clearance is independent of liver and kidney function, critically ill patients may still have exaggerated hemodynamic and respiratory responses—titrate carefully.
References
  • 1. Lexicomp. (2024). Remifentanil: Drug information. Wolters Kluwer.
  • 2. Glass, P. S., Gan, T. J., & Howell, S. (1999). A review of the pharmacokinetics and pharmacodynamics of remifentanil. Anesthesia & Analgesia, 89(4 Suppl), S7–S14.
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