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Description:  Potent opioid, rapid onset and short duration of action.

Third line opioid:  only for use with specialist advice.

Caution:  Do not confuse with Fentanyl.  Fentanyl is four times more potent than alfentanil.


1mg in 2ml
5mg in 10ml (not routinely used)

5mg in 1ml (high strength)


• Used as a subcutaneous infusion or sublingually.  (The ampoules can be opened and administered sublingually).
•  A high concentration preparation (5mg in 1ml) can be ordered.  Caution with high strength preparation; refer to local policy for its use.

Sublingual/buccal spray
5mg/5ml (1 metered dose = 140 micrograms)

5ml spray

Pharmacist can order spray on a named patient basis if advised by a palliative care specialist (check local health board for availability).

Alfentanil - Table 1 Preparations - Version 1 June 2014


  • Third line injectable opioid for moderate to severe opioid responsive pain in patients unable to tolerate morphine, diamorphine or oxycodone due to persistent side effects (eg. sedation, confusion, hallucinations, itch).
    (See: Pain management, Choosing & Changing opioids)
  • Injectable analgesic for moderate to severe, opioid responsive pain in patients with Stage 4-5 chronic kidney disease (eGFR <30ml/min), or severe acute renal impairment.
  • Episodic/ incident pain
    • Pain often related to a particular event (eg. movement, dressing changes); sudden in onset, can be severe, but may not last long.
    • Different from breakthrough pain occurring when the dose of regular analgesic has worn off.
    • Assessed and treated independently of the regimen used to manage any continuous/ background pain.


  • Liver impairment: reduced clearance.
    Dose reduction of 30-50% may be necessary.
  • Renal impairment: no dose reduction needed.
    Not removed by dialysis.

Drug interactions

  • Hepatic metabolism is reduced by grapefruit juice and a number of medications e.g. fluconazole, clarithromycin, erythromycin: check BNF.
  • Alcohol and CNS depressants increase side effects
  • Anticonvulsants may reduce its effect.  See BNF

Side effects

Similar to other opioids: nausea, dizziness, sedation, delirium, rarely respiratory depression.

Dose and Administration

  1. Alfentanil for moderate to severe opioid responsive pain
    • Continuous subcutaneous infusion in a CME T34 syringe pump over 24 hours.
    • Stability and compatibility – see: CME T34 syringe pump compatibility tables.
    • Titrate on the advice of a specialist.
    • Prescribe doses of over 1000 micrograms in milligrams (mg).
    • Prescribe about 1/10th to1/6th  of the 24hour dose hourly for breakthrough pain as alfentanil has a very short duration of action. The same dose can be given subcutaneously or sublingually. Sometimes other opioids with a longer duration of action are used for breakthrough pain.  Seek specialist advice if patient needs more than three ‘as required’ doses in 24 hours for breakthrough pain without acceptable benefit. 
  2. Alfentanil for episodic/ incident pain
    • Starting dose: 100 micrograms.
    • Give a dose five minutes before an event likely to cause pain; repeat if needed
    • Increase dose according to response.  This dose is titrated independently of the background dose.
    • Give by subcutaneous injection or sublingually. The dose is the same.
    • Consider an alfentanil spray if the patient is being discharged home (check local health board for availability).

Dose Conversions

  • Alfentanil is approximately thirty times more potent than oral morphine

Oral morphine 30mg

≈ subcutaneous alfentanil 1mg (1000 micrograms)

Subcutaneous morphine 15mg

≈ subcutaneous alfentanil 1mg (1000 micrograms)

Subcutaneous diamorphine 10mg

≈ subcutaneous alfentanil 1mg (1000 micrograms)

Oral oxycodone 15mg

≈ subcutaneous alfentanil 1mg (1000 micrograms)

Subcutaneous oxycodone 7.5mg

≈ subcutaneous alfentanil 1mg (1000 micrograms)

Alfentanil - Table 2 Conversions - Version 1 June 2014


A patient whose pain is controlled on a subcutaneous alfentanil infusion can be converted to a fentanyl patch. Apply the patch and stop the infusion 12 hours later. Seek advice for dose conversions.

  • Dose conversions should be conservative and doses rounded down.
  • Monitor the patient carefully so that the dose can be adjusted if necessary.
  • If the patient has opioid toxicity, reduce dose by approximately 1/3rd  when changing opioid. (See: Choosing & Changing opioids)

Practice Points

The community pharmacist, GP, and community nurse should be informed.

  • The unscheduled care service should be informed that the patient is receiving this third line opioid.
  • Alfentanil can be prescribed by the patient’s GP for the indications listed in liaison with local palliative care specialists.



Palliative Care Drug Information online: