Opioid Analgesic (Short-Acting) Pregnancy: Caution — crosses placenta; used for intrapartum analgesia with appropriate monitoring

Fentanyl (IV — Anaesthesia/ICU)

Brand names: Sublimaze

Adult dose

Dose: Induction supplement: 1–3 mcg/kg; Procedural analgesia: 25–100 mcg bolus; ICU infusion: 25–200 mcg/hour

Route: IV

Frequency: Bolus or continuous infusion

Max: Titrated to clinical response

Onset 3–5 min; duration 30–60 min (single bolus). Highly lipophilic — rapid CNS penetration. Preferred opioid in ICU for renal failure patients. Context-sensitive half-time markedly increases with prolonged infusion — accumulates significantly.

Paediatric dose

Dose: 1–5 mcg/kg

Route: IV

Frequency: Bolus or infusion

Max: Titrated to effect

Intraoperative analgesia: 1–5 mcg/kg. Neonates: 0.5–2 mcg/kg with caution — prolonged half-life in neonates.

Dose adjustments

Renal

Preferred opioid in renal failure — no active metabolite accumulation (unlike morphine-6-glucuronide). Monitor carefully.

Hepatic

Caution in severe hepatic impairment — reduced clearance and prolonged effect.

Paediatric weight-based calculator

Patient weight (kg)

Intraoperative analgesia: 1–5 mcg/kg. Neonates: 0.5–2 mcg/kg with caution — prolonged half-life in neonates.

Clinical pearls

Antidote: naloxone 0.4–2 mg IV (titrate carefully to avoid acute withdrawal)
In ICU: fentanyl preferred over morphine in AKI/CKD — no active metabolite accumulation
Context-sensitive half-time after 3-hour infusion approaches 300 min — plan ahead for extubation by reducing infusion rate early

Contraindications

Respiratory depression without ventilatory support
MAOIs within 14 days

Side effects

Respiratory depression
Chest wall rigidity (high-dose bolus)
Nausea/vomiting
Bradycardia
Accumulation with prolonged ICU infusion

Interactions

MAOIs (severe reaction — contraindicated)
CYP3A4 inhibitors (fluconazole, erythromycin — increase levels)
Benzodiazepines (marked synergism — respiratory depression)

Monitoring

SpO2, RR, BP
RASS sedation score in ICU
Pain scores (NRS)

Reference: BNFc; BNF 90; BNFc; FICM Guidelines on Analgesia/Sedation in ICU; Stoelting's Pharmacology. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways