Analgesic Pregnancy: C — neonatal respiratory depression risk if given within 4h of delivery

Fentanyl

Brand names: Sublimaze, Actiq, Duragesic

Adult dose

Dose: 25–100mcg IV (1–2mcg/kg); intranasal 1.5mcg/kg via MAD

Route: IV / Intranasal / Buccal

Frequency: PRN, repeat after 30–60 min as needed

Max: Titrate to effect

IV: 25–50mcg slow push over 3–5 min, reassess, titrate. Intranasal: 1.5mcg/kg via MAD device (max 200mcg). Infusion: 25–100mcg/h.

Dose: 1 mcg/kg

Route: IV / Intranasal

Frequency: PRN

Max: 50mcg

Concentration: 50 mcg/ml

Renal

Safe in renal impairment — no active metabolites. Preferred opioid in CKD and dialysis.

Hepatic

Reduce dose in severe hepatic impairment.

Paediatric weight-based calculator

Patient weight (kg)

100× more potent than morphine. 100mcg fentanyl ≈ 10mg morphine (IV equipotency).
Preferred analgesic in renal failure — no active metabolites unlike morphine (M6G).
Intranasal fentanyl 1.5mcg/kg via MAD equals IV morphine for paediatric fracture pain — avoids painful IV access.
Chest wall rigidity risk with rapid bolus >5mcg/kg — give over 3–5 min or have naloxone ready.
Short duration (IV 30–40 min) — advantages for procedural sedation and titrated analgesia.

CNS depressants: additive sedation and respiratory depression
MAOIs: potentially fatal interaction — absolutely contraindicated
CYP3A4 inhibitors (fluconazole, ritonavir): increase fentanyl levels and duration

Reference: BNFc; NICE BNF 84; RCEM Pain in Adults Clinical Standards 2022. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

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