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Continuing Education Activity

Alfentanil is a short-acting opioid analgesic commonly compared to fentanyl, a medication that is ubiquitous in the hospital setting along with remifentanil and sufentanil. It has FDA approval as an anesthetic agent in adults and children who are undergoing general anesthesia and monitored anesthesia care. This activity reviews the indications, target patient, administration, adverse effects, mechanism of action, and monitoring of alfentanil as part of an interprofessional strategy in pain management.


  • Identify the target patient population and appropriate scenario for alfentanil use.
  • Describe the mechanism of action of alfentanil.
  • Review the toxicity and appropriate monitoring of alfentanil.
  • Outline interprofessional team strategies for improving care coordination and communication in the use of alfentanil to improve outcomes in pain management where its use is indicated.


Alfentanil is a synthetic opioid analgesic and a derivative of fentanyl. It is widely used for analgesia to supplement general anesthesia for various surgical procedures, or as a primary anesthetic agent in very high doses during cardiac surgery.

Compared to similar anesthetics, including fentanyl and sufentanil, alfentanil is the least potent, has the fastest onset of action, and the shortest duration of action. Because of alfentanil’s short duration of action, it is typically preferred for shorter procedures, or when rapid changes in the level of consciousness are necessary. Such procedures include gynecological procedures, short ambulatory procedures such as colonoscopies, and shorter surgeries such as tonsillectomies, appendectomies, and cholecystectomies, to list a few. Alfentanil has demonstrated to be effective and safe in both children and adults at appropriate dosing.[1][2][3][4][5][6][7][8]

Mechanism of Action

Alfentanil is of the opioid class of medications and thus acts by stimulation of the opioid receptors, of which there are three main subtypes: mu (m), kappa (k), and delta (d). The receptor primarily involved in pain transmission is the m-opioid receptor. The opioid receptors are predominately present in the central nervous system, brain, and spinal column, and peripheral nervous system, but are also present on vascular, cardiac, lung, gut, and even peripheral blood mononuclear cells. The natural ligands for the opioid receptors are called the “endogenous opioid peptides” and include enkephalins, endorphins, and endomorphins.

Opioids have a variety of clinical effects but are predominately known and used for their profound pain-relieving effects. Their pain-relieving effects are from binding the m-opioid receptor, which is coupled to G1 proteins, resulting in the closure of N-type voltage-operated calcium channels and opening of calcium-dependent inwardly-rectifying potassium channels. The result is intracellular hyperkalemia and the decrease in the neurotransmission of pain signals resulting in increased tolerability of pain. Opioid receptor binding also decreases intracellular cyclic-adenosine-monophosphate (cAMP), which modulates the release of nociceptive (relating to the perception of pain) neurotransmitters (e.g., substance P).

There have not been acute changes to intracellular sodium noted to occur with opioid-receptor binding; however, intracellular sodium may hypothetically have involvement in opioid-receptor affinity to both endogenous and exogenous opioid-receptor binders. Researchers have observed that opioid-receptor binders seem to bind with a higher affinity in the presence of lower intracellular sodium concentrations and higher intracellular potassium concentrations. Of note, there was no observed change in the total number of binding sites of the opioid receptors during these observations. This phenomenon was observed specifically in cells known to have the m- and d-type opioid receptors.

Opioids are also known for their euphoric effects. Euphoria is a feeling or state of intense excitement and happiness. These effects usually are due to the binding of endorphins to opioid receptors in both the central and peripheral nervous systems. Endorphins are primarily synthesized and stored in the anterior pituitary gland from their precursor protein proopiomelanocortin (POMC). POMC is a large protein that is cleaved into smaller proteins such as beta-endorphin, alpha-melanocyte-stimulating hormone (MSH), adrenocorticotropin (ACTH), and others. Interestingly enough, studies have suggested that cells of the immune system are also capable of beta-endorphin synthesis because immune cells possess mRNA transcripts for POMC and T-lymphocytes, B-lymphocytes, monocytes, and macrophages have shown to contain endorphins during inflammation.

Normally, euphoric effects are primarily due to endorphin binding at opioid receptors in the peripheral nervous system. However, in opioid administration, it is directly due to opioid drugs binding the opioid receptors at both the pre- and postsynaptic junctional in the peripheral nervous system, and at the pre-synaptic junction in the central nervous system. The analgesia produced by endorphins in the peripheral nervous system mainly stems from a decreased synthesis of substance P. In the central nervous system, there is also a degree of analgesic effects from endorphins binding opioid receptors, but it is from inhibiting the release of GABA, resulting in excess production of dopamine. Upon opioid administration, the opioid drug takes on this role.

It bears mention that when administering opioid analgesic drugs to patients, there is a decrease in synthesis and secretion of endogenous endorphins and opioid peptides; this is due to negative feedback on the endogenous endorphin and opioid systems.  

Other effects of opioid medications include changes in mood, drowsiness, and mental clouding. However, the distinctive feature of the analgesia induced by opioids is the lack of consciousness. The patient still perceives pain but describes it as less intense. Thus, opioids do not decrease or treat the cause of a painful stimulus, but rather decrease its perception.[9][10][11][12][13][14][15]


Administration of alfentanil to adults is typically intravenous over three minutes or by continuous intravenous infusion, and administration to children is typically intravenous over three to five minutes, or by continuous intravenous infusion. However, other methods of administration of alfentanil have demonstrated efficacy, including epidural (injection into the epidural space), intrathecal (injection into the spinal canal or, into the subarachnoid space), transdermal (across the skin), and intranasal.[1]

Adverse Effects

With alfentanil being an opioid-class analgesic, it has adverse effects common to this group of medications, including respiratory depression, decreased gastrointestinal motility, sedation, nausea, vomiting, constipation, and intestinal bloating. An interesting note about alfentanil is that it causes less intense respiratory depression than fentanyl likely due to its lower total body clearance, smaller volume of distribution, and shorter half-life than other commonly used similar opioid analgesics, such as fentanyl and sufentanil. Additional adverse effects noted to be more specific to alfentanil include hypotension, chest wall rigidity, bradycardia, and tachycardia.[10][4][7]


Alfentanil is contraindicated in patients who have a history of hypersensitivity to alfentanil (e.g., anaphylaxis) or any component of the formulation. It is also contraindicated in those who have shown hypersensitivity to other similar opioid-class medications.

There has been evidence that alfentanil can increase the risk of seizures in those with a history of seizures and can increase the duration of seizures. In such patients, electroencephalogram monitoring may be necessary if another analgesic is unable to be used, but a history of seizures is not necessarily a contraindication to alfentanil.

Outside of the United States, specifically in Canada, contraindications to alfentanil include suspected abdomen surgery, mild pain that is manageable with other pain medications, acute/severe bronchial asthma, chronic obstructive airway, acute respiratory depression, status asthmaticus, hypercapnia, cor pulmonale, acute alcoholism, convulsive disorders, delirium tremens, severe CNS depression, increased intracranial or cerebrospinal pressure and head injury, or using monoamine-oxidase inhibitors, e.g., phenelzine concurrently or within 14 days of use, as well as women or who are nursing or pregnant, and during labor/delivery.[16][17]


Because of the adverse effects of alfentanil highlighted above, the recommendation is that vital signs undergo close monitoring for those receiving alfentanil, including respiratory status, cardiovascular status, blood pressure, and heart rate. These parameters should continue to be monitored closely immediately after surgery as well. Also, in those with a history of seizure activity, electroencephalogram monitoring may be necessary. This precaution is due to an observed focal activation of cerebral activity occasionally seen in those with seizure history who have received alfentanil.


Alfentanil toxicity symptoms are similar to that of other opioid-class medication toxicities and include rigidity of the skeletal muscles, cardiac depression, respiratory depression, and narrowing of the pupils.

If signs of toxicity develop, supportive measures should be deployed, including the reestablishment of a patent-protected airway (with ventilation if needed) and oxygen/vasopressors in the case of circulatory shock or pulmonary edema. Naloxone – an opioid receptor antagonist – is typically used for the reversal of alfentanil toxicity. Nalmefene is another antidote commonly used reversal agent in the case of opioid toxicity.[18]

Enhancing Healthcare Team Outcomes

It is a schedule two controlled substance, meaning it has a high potential for abuse, which can ultimately lead to psychosocial and/or physical dependence. Amid the current opioid abuse problem, it is important to implement harm-reducing strategies and technologies in the healthcare field. Interprofessional collaboration between every member of the team involved in the care of patients and utilizing prescription drug monitoring programs is the best way to watch for potential abuse of opioid drugs.[19][20][21]

Article Details

Article Author

Rajat Moman

Article Author

Myles Mowery

Article Editor:

Brendan Kelley


6/18/2021 6:22:53 AM

PubMed Link:




Scholz J,Steinfath M,Schulz M, Clinical pharmacokinetics of alfentanil, fentanyl and sufentanil. An update. Clinical pharmacokinetics. 1996 Oct     [PubMed PMID: 8896944]


Clotz MA,Nahata MC, Clinical uses of fentanyl, sufentanil, and alfentanil. Clinical pharmacy. 1991 Aug     [PubMed PMID: 1834393]


Hull CJ,Jacobson L, A clinical trial of alfentanil as an adjuvant for short anaesthetic procedures. British journal of anaesthesia. 1983     [PubMed PMID: 6418190]


Reitz JA, Alfentanil in anesthesia and analgesia. Drug intelligence & clinical pharmacy. 1986 May     [PubMed PMID: 3086065]


Türk HŞ,Aydoğmuş M,Ünsal O,Işıl CT,Citgez B,Oba S,Açık ME, Ketamine versus alfentanil combined with propofol for sedation in colonoscopy procedures: a randomized prospective study. The Turkish journal of gastroenterology : the official journal of Turkish Society of Gastroenterology. 2014 Dec     [PubMed PMID: 25599775]


Saarnivaara L,Klemola UM, Alfentanil as an adjuvant of balanced anaesthesia for tonsillectomy in adults. Acta anaesthesiologica Scandinavica. 1987 Jan     [PubMed PMID: 2881423]


Sfez M,Le Mapihan Y,Gaillard JL,Rosemblatt JM, Analgesia for appendectomy: comparison of fentanyl and alfentanil in children. Acta anaesthesiologica Scandinavica. 1990 Jan     [PubMed PMID: 2309538]


Karcioglu M,Davarci I,Tuzcu K,Bozdogan YB,Turhanoglu S,Aydogan A,Temiz M, Addition of ketamine to propofol-alfentanil anesthesia may reduce postoperative pain in laparoscopic cholecystectomy. Surgical laparoscopy, endoscopy & percutaneous techniques. 2013 Apr     [PubMed PMID: 23579518]


Owusu Obeng A,Hamadeh I,Smith M, Review of Opioid Pharmacogenetics and Considerations for Pain Management. Pharmacotherapy. 2017 Sep     [PubMed PMID: 28699646]


Fentanyl . 2012     [PubMed PMID: 31643358]


Bovill JG, Mechanisms of actions of opioids and non-steroidal anti-inflammatory drugs. European journal of anaesthesiology. Supplement. 1997 May     [PubMed PMID: 9202932]


Sprouse-Blum AS,Smith G,Sugai D,Parsa FD, Understanding endorphins and their importance in pain management. Hawaii medical journal. 2010 Mar     [PubMed PMID: 20397507]


Stein C, The control of pain in peripheral tissue by opioids. The New England journal of medicine. 1995 Jun 22     [PubMed PMID: 7760870]


Jessop DS, Beta-endorphin in the immune system--mediator of pain and stress? Lancet (London, England). 1998 Jun 20     [PubMed PMID: 9652661]


Mousa SA,Shakibaei M,Sitte N,Schäfer M,Stein C, Subcellular pathways of beta-endorphin synthesis, processing, and release from immunocytes in inflammatory pain. Endocrinology. 2004 Mar     [PubMed PMID: 14630714]


Cascino GD,So EL,Sharbrough FW,Strelow D,Lagerlund TD,Milde LN,O'Brien PC, Alfentanil-induced epileptiform activity in patients with partial epilepsy. Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society. 1993 Oct     [PubMed PMID: 8308147]


Akcaboy ZN,Akcaboy EY,Yigitbasł B,Bayam G,Dikmen B,Gogus N,Dilbaz N, Effects of remifentanil and alfentanil on seizure duration, stimulus amplitudes and recovery parameters during ECT. Acta anaesthesiologica Scandinavica. 2005 Sep     [PubMed PMID: 16095445]


Boyer EW, Management of opioid analgesic overdose. The New England journal of medicine. 2012 Jul 12     [PubMed PMID: 22784117]


Aro HJ,Bobrin BD, Controlled Substances . 2020 Jan     [PubMed PMID: 32119270]


Kuczyńska K,Grzonkowski P,Kacprzak Ł,Zawilska JB, Abuse of fentanyl: An emerging problem to face. Forensic science international. 2018 Aug     [PubMed PMID: 29902699]


Leichtling GJ,Irvine JM,Hildebran C,Cohen DJ,Hallvik SE,Deyo RA, Clinicians' Use of Prescription Drug Monitoring Programs in Clinical Practice and Decision-Making. Pain medicine (Malden, Mass.). 2017 Jun 1     [PubMed PMID: 27794549]