Remifentanil
Ultiva
Ultra-short-acting μ-opioid agonist
μ-opioid agonist. Ester linkage hydrolyzed by nonspecific tissue + plasma esterases — no organ-dependent clearance.
Indications
- •TIVA component
- •Cardiac surgery analgesia
- •Awake fiberoptic intubation
- •OB GA cesarean (sometimes)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Bolus | 0.5–1 mcg/kg IV (slow over 30 sec) | — |
| Infusion | 0.05–0.5 mcg/kg/min | — |
| MAC sedation | 0.025–0.1 mcg/kg/min | — |
Pharmacokinetics
Onset 1 min. Context-sensitive half-time 3–4 min regardless of duration.
Hemodynamic effects
↓HR + ↓BP at high infusion rates.
Respiratory effects
Profound respiratory depression — must be paired with controlled ventilation or vigilant MAC.
Side effects
- !Acute opioid tolerance + post-infusion hyperalgesia (dose-dependent)
- !Bradycardia, hypotension
- !Chest wall rigidity (most reported of all opioids)
- !No residual postop analgesia → plan transition opioid before stopping
Contraindications
- ×No known absolute
Clinical pearls
- ★Bridge to long-acting analgesic (morphine 0.1–0.15 mg/kg or hydromorphone 10–20 mcg/kg) ~30 min before stop.
- ★Useful in hepatic + renal failure (organ-independent clearance).
- ★Co-infuse with propofol for TIVA — avoid oversedation by titrating each separately.
Other drugs in Narcotics & Analgesics
- Fentanyl
μ-opioid receptor agonist. ~100× potency of morphine.
- Morphine
μ-opioid receptor agonist. Active metabolite morphine-6-glucuronide (M6G) is analgesic and renally cleared — accumulates in renal failure → prolonged sedation/respiratory depression. Causes histamine release.
- Hydromorphone
μ-opioid agonist ~5–7× more potent than morphine. No clinically significant active metabolites → safer than morphine in renal failure. Less histamine release.
- Sufentanil
Most potent opioid in common clinical use — ~1000× morphine, ~10× fentanyl. High lipid solubility.
- Alfentanil
μ-opioid agonist ~1/5–1/10 the potency of fentanyl but FASTEST onset of the family — low pKa means a high non-ionized fraction at physiologic pH.
- Meperidine
μ-opioid agonist ~1/10 morphine, plus κ-agonism (anti-shivering). Active metabolite normeperidine is renally cleared, proconvulsant, and neurotoxic.
- Methadone
μ-opioid agonist with NMDA-receptor antagonism (blunts tolerance + opioid-induced hyperalgesia) and monoamine reuptake inhibition. Very long, variable half-life.
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •Miller's Anesthesia, 9e
- •FDA package insert
