Skip to content
ClinCalc Pro
Menu
Calculators Drugs Pathways AI Dx Donate Get the App
Opioid Analgesic

Fentanyl

Brand names: Sublimaze, PecFent (intranasal)

Fentanyl is a potent short-acting synthetic opioid used in children for procedural and intraoperative analgesia, sedation in intensive care and for severe pain, by intravenous, intranasal and transmucosal routes.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Verbatim §2 highlights: 'Initiate treatment in adults with 50 mcg to 100 mcg.' Premedication: 50 to 100 micrograms intramuscularly 30 to 60 minutes prior to surgery. Adjunct to regional anaesthesia: 50 to 100 micrograms IM or slowly IV over one to two minutes when additional analgesia is required. Postoperatively (recovery room): 50 to 100 micrograms IM for the control of pain, tachypnoea and emergence delirium, repeatable in one to two hours as needed.
Route: Intravenous or intramuscular injection (50 micrograms of fentanyl base per mL). Verbatim §2.1: 'Fentanyl Citrate Injection should be administered only by persons specifically trained in the use of intravenous anesthetics and management of the respiratory effects of potent opioids.' 'Do not dilute for IV push.' The intranasal route shown on this page is not covered by this label.
Frequency: Titrated to effect; maintenance doses of 25 to 100 micrograms IV or IM 'as needed when movement and/or changes in vital signs indicate surgical stress or lightening of analgesia'; postoperative doses may be repeated in one to two hours.
US labelling only — no UK SPC in this bundle. §2.2 Dosage Range Chart, verbatim: 'Low Dose — 2 mcg/kg. For use in minor, but painful, surgical procedures. May also provide some pain relief in the immediate postoperative period. Moderate Dose — 2 mcg/kg to 20 mcg/kg. For use in more major surgical procedures... Expect respiratory depression requiring artificial ventilation during anesthesia. High dose — 20 mcg/kg to 50 mcg/kg. For open heart surgery and certain more complicated neurosurgical and orthopedic procedures... Expect the need of postoperative ventilation.' As a sole general anaesthetic: 'doses of 50 mcg/kg to 100 mcg/kg may be administered with oxygen and a muscle relaxant. In certain cases, doses up to 150 mcg/kg may be necessary to produce this anesthetic effect.' Those high-dose figures are anaesthetic regimens, not ED analgesia. 'Individualize dosage based on factors such as age, body weight, physical status, underlying pathological condition, use of other drugs, type of anesthesia to be used, and the surgical procedure involved.' NO MAXIMUM DOSE is stated in this label, so no ceiling is published. §8.5: elderly patients may have increased sensitivity — start at the low end of the dosing range and titrate slowly.

Paediatric dose

Dose: 2 micrograms/kg
Route: Intravenous or intramuscular — children 2 to 12 years of age (induction and maintenance of anaesthesia)
Frequency: Titrated to effect, as part of an anaesthetic technique
Concentration: 50 micrograms/ml
The calculator uses the LOWER end of the label's stated range. Verbatim §2.2: 'For Induction and Maintenance in Children 2 to 12 Years of Age — A reduced dose as low as 2 mcg/kg to 3 mcg/kg is recommended', and §2 highlights: 'Initiate treatment in children 2 to 12 years of age, with a reduced dose as low as 2 mcg/kg to 3 mcg/kg.' AGE LIMIT, verbatim §8.4: 'The safety and efficacy of Fentanyl Citrate Injection in pediatric patients under two years of age has not been established. Rare cases of unexplained clinically significant methemoglobinemia have been reported in premature neonates undergoing emergency anesthesia and surgery which included combined use of fentanyl, pancuronium and atropine.' No figure for neonates or infants under 2 years is published here, and none appears in this label. The label gives no INTRANASAL dose — the 1.5–2 micrograms/kg intranasal regimen previously shown on this page is not supported by any fetched source and has been dropped. The concentration used for the volume calculation is the labelled strength: 'Fentanyl Citrate Injection, USP, equivalent to 50 mcg fentanyl base per mL'. Administration must be by 'persons specifically trained in the use of intravenous anesthetics and management of the respiratory effects of potent opioids', with an opioid antagonist, resuscitative and intubation equipment and oxygen readily available. Verify all under-18 dosing against a children's formulary before administration.

Dose adjustments

Renal

Not stated — this label has no renal-impairment dosing section. The only relevant text is §8.5 (geriatric use), verbatim: 'Fentanyl is known to be substantially excreted by the kidney, and the risk of adverse reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.' Verify against a UK SPC before relying on any renal dose adjustment.

Hepatic

Not stated — no hepatic-impairment dosing statement appears in any fetched section of this label; §8.5 mentions only that elderly patients more often have 'decreased hepatic, renal, or cardiac function'. Verify against a UK SPC.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

The calculator uses the LOWER end of the label's stated range. Verbatim §2.2: 'For Induction and Maintenance in Children 2 to 12 Years of Age — A reduced dose as low as 2 mcg/kg to 3 mcg/kg is recommended', and §2 highlights: 'Initiate treatment in children 2 to 12 years of age, with a reduced dose as low as 2 mcg/kg to 3 mcg/kg.' AGE LIMIT, verbatim §8.4: 'The safety and efficacy of Fentanyl Citrate Injection in pediatric patients under two years of age has not been established. Rare cases of unexplained clinically significant methemoglobinemia have been reported in premature neonates undergoing emergency anesthesia and surgery which included combined use of fentanyl, pancuronium and atropine.' No figure for neonates or infants under 2 years is published here, and none appears in this label. The label gives no INTRANASAL dose — the 1.5–2 micrograms/kg intranasal regimen previously shown on this page is not supported by any fetched source and has been dropped. The concentration used for the volume calculation is the labelled strength: 'Fentanyl Citrate Injection, USP, equivalent to 50 mcg fentanyl base per mL'. Administration must be by 'persons specifically trained in the use of intravenous anesthetics and management of the respiratory effects of potent opioids', with an opioid antagonist, resuscitative and intubation equipment and oxygen readily available. Verify all under-18 dosing against a children's formulary before administration.

Verify in a children's formulary

Contraindications

  • Hypersensitivity to fentanyl (e.g. anaphylaxis) — §4, the only contraindication stated in this US label
  • SCOPE NOTE: this US label's §4 is shorter than the UK injection SPC's, which additionally contraindicates respiratory depression, obstructive airways disease, and MAOI use within the preceding 2 weeks. That UK SPC is not in this bundle

Side effects

  • §6, verbatim: 'As with other opioid agonists, the most common serious adverse reactions reported to occur with fentanyl are respiratory depression, apnea, rigidity and bradycardia; if these remain untreated, respiratory arrest, circulatory depression or cardiac arrest could occur.' Other reported reactions include hypertension (the list was truncated at the source-fetch limit)
  • Skeletal muscle rigidity and skeletal muscle movement (§5.5) — 'Manage with neuromuscular blocking agent'
  • Severe cardiovascular depression (§5.6) — monitor during dosage initiation and titration
  • Opioid-induced hyperalgesia and allodynia (§5.7) — 'If OIH is suspected, carefully consider appropriately decreasing the dose of the current opioid analgesic, or opioid rotation'
  • Serotonin syndrome (§5.8) — 'Potentially life-threatening condition could result from concomitant serotonergic drug administration. Discontinue Fentanyl Citrate Injection if serotonin syndrome is suspected'
  • Adrenal insufficiency (§5.9) — 'If diagnosed, treat with physiologic replacement of corticosteroids, and wean patient off of the opioid'
  • Addiction, abuse and misuse (§5.1); life-threatening respiratory depression (§5.2); interactions with benzodiazepines and other CNS depressants (§5.3); gastrointestinal adverse reactions (§5.11); seizures (§5.12)

Monitoring

  • §2.1, verbatim: 'Ensure that an opioid antagonist, resuscitative and intubation equipment, and oxygen are readily available.'
  • §2.1, verbatim: 'Monitor vital signs routinely. As with other potent opioids, the respiratory depressant effect of fentanyl may persist longer than the measured analgesic effect.'
  • Increased intracranial pressure, brain tumours or head injury (§5.10) — 'Monitor for sedation and respiratory depression'
  • Severe cardiovascular depression (§5.6) — 'Monitor during dosage initiation and titration'
  • With a CYP3A4 inhibitor (§7): 'Monitor patients at frequent intervals for respiratory depression and sedation'; if the inhibitor is stopped, monitor for signs of opioid withdrawal
  • Renal function in elderly patients (§8.5) — 'it may be useful to monitor renal function'

Clinical monograph

How it works

It is a strong mu-opioid receptor agonist, producing rapid analgesia and sedation with a fast onset and short duration after a single dose.

Prescribing in practice

  • The dominant risk is dose-dependent respiratory depression, which can be profound and delayed, so it must be given with monitoring, resuscitation equipment and naloxone available and titrated carefully.
  • Rapid intravenous administration can cause chest-wall rigidity impairing ventilation, and effects are potentiated by other sedatives and CNS depressants.
  • Use weight-based dosing from a children's formulary and reserve transdermal formulations for opioid-tolerant children with stable chronic pain.

Monitoring

Continuously monitor respiratory rate, oxygen saturation, sedation level and blood pressure during and after administration.

Counselling the patient

  • Drowsiness and slowed breathing can occur, so the child must be observed closely.
  • Carers of children on patches should keep used and unused patches away from others and dispose of them safely.
  • Report any difficulty breathing, excessive sleepiness or unresponsiveness immediately.

Evidence & guidelines

Fentanyl is widely used for paediatric procedural and perioperative analgesia, with dosing and monitoring directed by specialist anaesthetic and intensive care practice.

Reference: RCEM Paediatric Pain Guidelines; Borland et al. (2007) intranasal fentanyl evidence; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

Calculators
Pathways