This site is intended for UK healthcare professionals
Medscape UK Univadis Logo
Medscape UK Univadis Logo

Alfentanil injection 500micrograms/ml


Injections of alfentanil hydrochloride containing 500micrograms per ml.

Drugs List

  • alfentanil 1mg/2ml injection
  • alfentanil 25mg/50ml solution for injection vial
  • alfentanil 5mg/10ml injection
  • RAPIFEN 1mg/2ml injection
  • RAPIFEN 5mg/10ml injection
  • Therapeutic Indications


    Analgesia for painful procedures
    Analgesic agent during induction and/or maintenance of general anaesthesia

    Analgesic supplement before and during anaesthesia in:
    Short procedures and outpatient surgery.
    Procedures of medium to long duration when given as a bolus injection followed by supplemental doses or infusion.

    Neonates, infants and children in:
    association with a hypnotic to induce anaesthesia
    association with general anaesthesia and for both short and long surgical procedures.

    It may be used for anaesthetic induction agent in ventilated patients (at very high doses).


    Should be used as bolus injections (short procedures) or bolus supplemented by increments or by infusion (long painful surgical procedures).

    Dose should be adjusted according to each individual patient.


    Spontaneous respiration
    Initial dose: 500micrograms, administered slowly over 30 seconds.
    Supplemental doses: 250micrograms

    Assisted ventilation for short procedures
    Initial dose: 30micrograms/kg to 50micrograms/kg.
    Supplemental doses: 15micrograms/kg.

    The last dose should be administered at least 10 minutes before the end of the procedure.

    Assisted ventilation for longer procedures
    Loading dose: 50micrograms/kg to 100micrograms/kg, given as a bolus or rapid infusion over a period of 10 minutes. Maintenance infusion rate of 0.5 to 1microgram/kg per minute.
    Lower doses may be adequate e.g. during concomitant use with other agents.

    Discontinue the infusion 30 minutes before the anticipated end of surgery.


    Children aged 12 to 18 years
    (See Dosage; Adult)

    Children from Birth to 12 years
    Rate of infusion may need to be increased, adjust according to each individual patient response.

    The following dosing schedule may also be suitable:
    Children aged 1 month and 18 years
    Assisted ventilation for short procedures by injection
    Initial dose: 10micrograms/kg to 20micrograms/kg over 30 seconds.
    Supplemental doses may be administered up to 10micrograms/kg.

    Assisted ventilation: longer procedures by infusion
    Initial dose: 50micrograms/kg to 100micrograms/kg over 10 minutes.
    Maintenance dose: 30micrograms/kg to 120micrograms/kg per hour.


    Assisted ventilation for short procedures by injection
    Initial dose: 5micrograms/kg to 20micrograms/kg over 30 seconds.
    Supplemental doses may be administered up to 10micrograms/kg.

    Assisted ventilation for longer procedures by infusion
    Initial dose: 10micrograms/kg to 50micrograms/kg over 10 minutes.
    Maintenance dose: 30micrograms/kg to 60micrograms/kg per hour.

    Additional Dosage Information

    Due to the longer half-life of alfentanil in debilitated patients, lower or less frequent doses may be required and dilution may be helpful.

    Periods of more painful stimuli may be overcome with small increments of alfentanil. For patients receiving an infusion, supplementation with bolus alfentanil doses or brief periods of low concentrations of a volatile agent are preferable to increasing the infusion rate (may prolong recovery).


    For intravenous administration by injection or infusion.

    Induction doses should be infused slowly over 3 minutes. An increased incidence of hypotension has been associated with rates of less than one minute.


    Risk of paralytic ileus
    Within 2 weeks of discontinuing MAOIs
    Head trauma
    Non-ventilated obstructive pulmonary disease
    Non-ventilated respiratory depression
    Raised intracranial pressure

    Precautions and Warnings

    Children under 18 years
    Adrenal insufficiency
    Benign prostatic hyperplasia
    Biliary tract disorder
    Drug misuse
    Gastrointestinal obstruction
    Hepatic impairment
    History of drug misuse
    Inflammatory bowel disease
    Myasthenia gravis
    Opioid dependence
    Psychiatric disorder
    Pulmonary disease
    Reduced intracerebral compliance
    Reduced respiratory reserve
    Renal impairment
    Severe burn
    Urethral stricture

    Reduce dose in hypothyroidism
    Reduce dose in patients with hepatic impairment
    Reduce dose in patients with renal impairment
    Advise ability to drive/operate machinery may be affected by side effects
    Advise patient not to drive until they know how the medicine affects them
    Advise patient not to drive/operate machinery within 24 hours of treatment
    Advise patient this medicine may be subject to driving restrictions
    Avoid within 2 weeks of discontinuing a MAOI
    Excess muscle rigidity: Administer neuromuscular blocker and/or hypnotic.
    Resuscitation facilities must be immediately available
    Treatment to be administered by or under supervision of specialist
    Always administer by slow intravenous injection or infusion
    May cause respiratory depression
    Monitor at regular intervals as withdrawal symptoms & dependence may occur
    Monitor patient for signs and symptoms of respiratory depression
    Monitor patients on prolonged therapy
    Monitor patients with a history of alcoholism and drug abuse
    Monitor post operative patients for respiratory and other side effects
    Monitor vital signs, respiration & cardiac function
    Neonate exposed in utero: Monitor for neonatal withdrawal syndrome
    Reduce dose if bradycardia develops
    Tolerance and dependence may occur
    When used with SSRIs, risk of Serotonin syndrome
    Discontinue or reduce rate in muscle rigidity
    Neonate exposed in labour: Risk of respiratory depression
    Prolonged use at high doses may result in hyperalgesia
    Progressive withdrawal recommended
    Interrupt infusion if hypotension occurs
    Consider dose reduction or alternative opioid in cases of hyperalgesia
    In obese patients dosing should be based on ideal weight
    Not licensed for all indications in all age groups
    Reduce dose in debilitated patients
    Reduce dose in elderly
    Advise patient to avoid alcohol during treatment
    Advise that effects are potentiated by CNS depressants (including alcohol)

    A fall in blood pressure may occur which may exaggerated in the hypovolaemic patient or in the presence of concomitant sedative medication. Appropriate measures to maintain a stable arterial pressure should be taken.

    Significant respiratory depression and loss of consciousness will occur following doses of alfentanil exceeding 1mg, and this effect is dose related. This effect is usually short in duration and can be reversed by specific opioid antagonists, such as naloxone. The duration of respiratory depression may last for longer than the opioid antagonist action, therefore additional doses of the antagonist may be required.

    Alfentanil may cause bradycardia, an effect that may be marked and rapid in onset but which can be antagonised by atropine. Particular care must be taken following treatment with drugs which may depress the heart or increase vagal tone, such as anaesthetic agents or beta-blockers.

    Cardiac arrest following bradycardia has been reported on very rare occasions in non-atropinised patients. Therefore it is advisable to be prepared to administer an anticholinergic drug.

    Patients on chronic opioid therapy or with a history of opioid abuse may require higher doses.

    Rapid bolus injections should be avoided in patients with compromised intracerebral compliance. A transient decrease in the mean arterial pressure, occasionally with a transient reduction of the cerebral perfusion pressure, may be experienced in these patients.

    Hyperventilation during anaesthesia may alter the patient's response to carbon dioxide and affect respiration after the procedure.

    Non-epileptic (myo)clonic movements may occur.

    There maybe a higher risk of respiratory complications when alfentanil is administered to neonates and very young children than when it is used in older children and adults. Young paediatric subjects should be monitored immediately after administration of alfentanil is commenced.

    Risk of muscle rigidity in neonates and young infants. All children should be monitored for a sufficient period of time following cessation of treatment with alfentanil to ensure the return of spontaneous respiration has been achieved.

    Pregnancy and Lactation


    Use alfentanil with caution during pregnancy.

    The manufacturer advises caution when prescribing alfentanil during pregnancy.

    At the time of writing there is limited published information regarding the use of alfentanil during pregnancy. Alfentanil crosses the placenta, and regular use during pregnancy may result in drug dependence in the foetus and withdrawal symptoms in the neonate. Use of alfentanil during labour may result in respiratory depression in the neonate. Animal studies have not shown teratogenic or acute embryotoxic effects.


    The use of alfentanil is contraindicated during breastfeeding.

    The manufacturer does not recommend the use of alfentanil during breastfeeding. Alfentanil is secreted into breast milk, and may cause respiratory depression in the breastfeed infant.

    LactMed (2018) states that there is limited data regarding intravenous use thus alternative agents are preferred. If alfentanil is used during breastfeeding and the infant shows signs of increased sleepiness (more than usual), difficulty breastfeeding, breathing difficulties, or limpness, a physician should be contacted immediately.

    Effects on Ability to Drive and Operate Machinery

    This class of medicine is in the list of drugs included in regulations under 5a of the Road Traffic Act 1988 (England and Wales). When prescribing this medicine: Advise patient the medicine can affect cognitive function and is likely to affect ability to drive. Advise patient not to drive until they know how the medicine affects them.

    Side Effects

    Allergic dermatitis
    Biliary spasm
    Cardiac arrest
    Circulatory failure
    Decrease in heart rate
    Difficulty in micturition
    Dry mouth
    Elevation of liver enzymes
    Hypersensitivity reactions
    Local pain (injection site)
    Mood changes
    Movement disturbances
    Muscle rigidity
    Myoclonic movements
    Postural hypotension
    Raised intracranial pressure
    Respiratory arrest
    Respiratory depression
    Sensation of cold
    Sexual dysfunction
    Sleep disturbances
    Ureteric spasm
    Urinary retention
    Visual disturbances


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: September 2018

    Reference Sources

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Summary of Product Characteristics. Alfentanil 500microgram/ml solution for injection. Hameln Pharmaceuticals Ltd. Revised July 2018.

    Summary of Product Characteristics. Rapifen 500micrograms/ml solution for injection or infusion. Piramal Critical Care Ltd. Revised August 2020.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Alfentanil Last revised: 31 October 2018
    Last accessed: 20 May 2021 Government departments. Department for Transport. Publications. Drug driving and medicine: Advice for healthcare professionals. Drug driving: Guidance for healthcare professionals on drug driving. Available at: Last accessed: 07 September 2018
    New drug driving offence. Implications for medicines packaging. Medicines Regulatory News. 10 December 2013. Available at: Last accessed: 07 September 2018

    NICE Evidence Services Available at: Last accessed: 07 September 2018

    Access the full UK drug database with a FREE Medscape UK Account
    It takes just a few minutes, and you’ll get unlimited access to information on over 11,000 UK drugs.
    Register for Free

    Already a member? Log in

    Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content

    FDB Logo

    FDB Disclaimer : FDB Multilex is intended for the use of healthcare professionals and is provided on the basis that the healthcare professionals will retain FULL and SOLE responsibility for deciding what treatment to prescribe or dispense for any particular patient or circumstance.