What it isEsterase-cleared mu-opioid agonist; tightly titratable analgesia during anesthesia.
Why this oneRecovery remains rapid after prolonged infusion and does not depend on hepatic or renal clearance.
What limits it⚑ Analgesia ends abruptly, so longer coverage must precede discontinuation; hyperalgesia, respiratory depression, and chest rigidity can occur.
BOXED WARNING Addiction, abuse, and misuse; life-threatening respiratory depression; profound sedation/respiratory depression/death with concomitant benzodiazepines or other CNS depressants
FDA dosing
Population
Start
Target
Max
Analgesic during induction/maintenance of general anesthesia
Adults
Continuous IV infusion, titrated to effect (see full PI tables)
Titrate to effect
Per PI
Analgesic component of anesthesia
Geriatric >65 y
Decrease starting dose by 50%
Titrate to effect
Per PI
Analgesic component of anesthesia
Pediatric
Weight-based (see PI)
Titrate to effect
Per PI
Renal No specific adjustment; titrate to effect (caution in renal impairment)
Hepatic Undefined
Instructions
IV use only; must be diluted before use
Continuous infusions via infusion device only
IV bolus only during maintenance of general anesthesia
Reduce starting dose by 50% in patients >65 y
Not for epidural or intrathecal use
Contraindications
Epidural or intrathecal administration (glycine in formulation)
Cautions
Life-threatening respiratory depression
Hypotension/sedation/death with concomitant benzodiazepines or CNS depressants
Opioid-induced hyperalgesia and allodynia
MAOIs due to risk of serotonin syndrome
Skeletal muscle rigidity
Bradycardia
Hypotension
Biliary tract disease
Seizures
Adverse reactions
Respiratory depression
Bradycardia
Hypotension
Skeletal muscle rigidity
Pregnancy Insufficient human data; prolonged use may cause neonatal opioid withdrawal
Lactation Unknown if excreted in human milk; monitor breastfed infant for sedation/respiratory depression