Alfentanil is a short-acting opioid analgesic used as an adjunct to barbiturates and nitrous oxide for the maintenance of analgesia. It is also used as an anesthetic agent for the induction of anesthesia in patients who require mechanical ventilation and endotracheal intubation.

The dose of Alfentanil should be titrated according to the desired analgesic/anesthetic effect. Anesthesia: The dose should be based on actual body weight. The induction dose should be administered slowly over 3 - 5 minutes. Injecting alfentanil rapidly may result in hypotension secondary to loss of vascular tone.

Alfentanil Dosage Range for Use During Anesthesia

DOSAGE GUIDELINES DOSAGE SHOULD BE INDIVIDUALIZED AND TITRATED

Note: Alfentanil dose should be titrated to achieve the desired degree of analgesia and sedation. Alfentanil for Anesthesia:

• Children 12 years of age or less: 10 to 20 mcg/kg/dose.
• For Procedural analgesia (LP or bone marrow aspiration): Intermittent intravenous infusion of 2 to 3 mcg/kg/dose (total dose range: 1.8 to 9.6 mcg/kg)
• Children ≥12 years and Adolescents: See the table below

Alfentanil Dosing

Pregnancy Risk Factor C

Alfentanil may cross the placental boundary and cause serious adverse effects in newborns, including respiratory depression. When used to relieve pain, it can also affect the heart rate. Manufacturers recommend that you avoid alfentanil immediately before or during labor.

Alfentanil during Breastfeeding

Breastmilk can contain significant amounts of alfentanil. Manufacturers recommend that you weigh the benefits of breastfeeding and the risks for the infant as well as the benefits to the mother from treatment.

Monitor infants who have been exposed to alfentanil in large amounts for prolonged periods of time for impaired suckling reflexes, sedation and apnea. The manufacturer has not recommended any dose adjustment in patients with renal disease. Although dose adjustment is not necessary, it should be used with caution.The manufacturer has not advised any dose adjustment in liver disease, however, it should be used with caution and the dose should be reduced.

Common side effects of alfentanil:

• Cardiovascular: Hypertension, Truncal rigidity, and bradycardia/ tachycardia
• Gastrointestinal: Nausea and vomiting.

Less common side effects:

• Cardiovascular: Hypotension and cardiac arrhythmia
• Central nervous system: Dizziness, drowsiness, euphoria and sedation
• Neuromuscular & skeletal: Muscle Movements, truncal rigidity, and myoclonus
• Ophthalmic: Blurred vision, miosis
• Respiratory: Apnea and respiratory depression
• Gastrointestinal: Constipation

Contraindications   

• Severe allergic reactions (or any component) to alfentanil and/or the formulation
• Suspected surgical abdomen (acute or chronic pancreatitis, appendicitis).
• Mild pain can be managed by simple analgesics
• Acute chest conditions such as severe bronchial asthma and chronic obstructive pulmonary disease, and status asthmaticus
• Hypercapnia, acute respiratory depression, and cor Pulmonale
• Acute alcoholism, delirium tremens, and seizure disorders
• Severe CNS depression
• Elevated intracranial pressure and head injuries
• Concurrent use a MAO inhibitor
• Nursing, pregnant or in labor and delivery for women

Warnings and Precautions

• HypotensionHypotension can occur in patients with heart disease, hypovolemia, or those taking anti-hypertensive medications. This is especially true if the drug was given as a rapid injection.
• Serotonin syndrome:Patients who take SSRIs, SNRIs or triptans may develop life-threatening serotonin Syndrome (SS) if they are taking 5-HT receptor antagonists, mirtazapine and trazodone.
• Conditions of the abdomen: May obscure the diagnosis or course of acute abdominal conditions.
• Insufficiency of the biliary tractAlfentanil may cause constriction in the sphincter Oddi, as with other opioids. Patients with biliary disease should not use it.
• Bradyarrhythmias: Alfentanil may cause bradycardia.
• Take carePatients with delirium, psychosis, seizures and liver disease should be treated with caution.
• Skeletal muscle rigidity:High doses of Alfentanil can cause muscular, especially truncal rigidity.
• Patients with a history of heart disease should be cautiousThyroid dysfunction and concurrent use of benzodiazepines

Other warnings & precautions:

• Alfentanil can lead to addiction.Opioid addiction can lead to death and overdose.

 Alfentanil: Drug Interaction

Note: Drug Interaction Categories:

• Risk Factor C: Monitor When Using Combination
• Risk Factor D: Consider Treatment Modification
• Risk Factor X: Avoid Concomitant Use
  •  

  Risk Factor C (Monitor therapy).
  Alizapride	CNS Depressants may increase the CNS depressant effects.
  Amphetamines	May increase the analgesic effects of Opioid Agonists.
  Anticholinergic Agents	This combination may increase the toxic/adverse effects of Opioid Agonists. This combination may increase the risk of constipation or urinary retention.
  Aprepitant	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Beta-Blockers	Anilidopiperidine, an opioid, may increase the bradycardic effects of Beta-Blockers. Anilidopiperidine and Opioids may increase the hypotensive effects of Beta-Blockers.
  Brimonidine (Topical)	CNS Depressants may increase the CNS depressant effects.
  Bromopride	CNS Depressants may increase the CNS depressant effects.
  Calcium Channel Blockers (Nondihydropyridine	Opioids (Anilidopiperidine) may enhance the bradycardic effect of Calcium Channel Blockers (Nondihydropyridine). Opioids (Anilidopiperidine) may enhance the hypotensive effect of Calcium Channel Blockers (Nondihydropyridine).
  Cannabidiol	CNS Depressants may increase the CNS depressant effects.
  Cannabis	CNS Depressants may increase the CNS depressant effects.
  Chlorphenesin Carbamate	CNS Depressants may have an adverse/toxic effect that can be exacerbated by them.
  Cimetidine	May increase the serum concentration of Alfentanil.
  Clofazimine	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Moderate CYP3A4 inhibitors	Might decrease metabolism of CYP3A4 substrates (High Risk with Inhibitors).
  Desmopressin	Desmopressin's toxic/adverse effects may be exacerbated by Opioid Agonists.
  DiazePAM	May enhance the CNS depressant effect of Alfentanil. Hypotension can also occur.
  DilTIAZem	May increase the serum concentration of Alfentanil.
  Dimethindene (Topical).	CNS Depressants may increase the CNS depressant effects.
  Diuretics	Opioid Agonists can increase the toxic/adverse effects of Diuretics. Opioid Agonists can decrease the therapeutic effects of Diuretics.
  Dronabinol	CNS Depressants may increase the CNS depressant effects.
  Duvelisib	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Fosaprepitant	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Fosnetupitant	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Gastrointestinal Agents (Prokinetic)	Opioid Agonists can decrease the therapeutic effects of Gastrointestinal Agents.
  Kava Kava	CNS Depressants may have an adverse/toxic effect that can be exacerbated by them.
  Larotrectinib	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Lofexidine	CNS Depressants may have a greater depressant effect on the brain. Management: Separate drug interaction monographs are available for drugs listed as an exception to this monograph.
  Magnesium Sulfate	CNS Depressants may increase the CNS depressant effects.
  MetyroSINE	CNS Depressants may enhance the sedative effect of MetyroSINE.
  Minocycline	CNS Depressants may increase the CNS depressant effects.
  Nabilone	CNS Depressants may increase the CNS depressant effects.
  Netupitant	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Palbociclib	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Pegvisomant	Pegvisomant's therapeutic effects may be diminished by Opioid Agonists.
  Piribedil	CNS Depressants could increase the CNS depressant effects of Piribedil.
  Pramipexole	Pramipexole may have a greater sedative effect if it is combined with CNS depressants.
  Propofol	Propofol's toxic/adverse effects may be increased by Alfentanil. Particularly, the development of opisthotonus (severe hyperextension or spasticity that results in arching or bridge position) and/or tonic-clonic seizures.
  Ramosetron	Ramosetron's constipating effects may be enhanced by Opioid Agonists.
  ROPINIRole	CNS Depressants can increase the sedative effects of ROPINIRole.
  Rotigotine	CNS Depressants can increase the sedative effects of Rotigotine.
  Rufinamide	CNS Depressants may have an adverse/toxic effect that can be exacerbated by this. Particularly, dizziness and sleepiness may be increased.
  Selective Serotonin Reuptake inhibitors	CNS Depressants can increase the toxic/adverse effects of Selective Serotonin Resuptake Inhibitors. Particularly, psychomotor impairment could be increased.
  Serotonin Modulators	Serotonin modulators may be enhanced by Opioid Agonists. This could lead to serotonin syndrome. Nicergoline is an exception.
  Simeprevir	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Succinylcholine	May increase the bradycardic effects of Opioid Agonists.
  Tetrahydrocannabinol	CNS Depressants may increase the CNS depressant effects.
  Tetrahydrocannabinol, and Cannabidiol	CNS Depressants may increase the CNS depressant effects.
  Risk Factor D (Consider therapy modifications)
  Alvimopan	Alvimopan's toxic/adverse effects may be exacerbated by Opioid Agonists. Patients who have been taking opiates for more than seven days prior to Alvimopan initiation will be most affected. Patients who have been receiving opioids for more that 7 days consecutively prior to alvimopan initiation are not advised to take Alvimopan.
  Blonanserin	CNS Depressants can increase the CNS depressant effects of Blonanserin.
  Chlormethiazole	CNS Depressants may increase the CNS depressant effects. Monitoring: Look out for signs of CNS depression. If a combination of chlormethiazole and other drugs is required, a reduced dose should be used.
  CNS Depressants	This may increase the CNS depressant effects of Opioid Agonists. Management: When possible, avoid the simultaneous use of opioid agonists and other CNS depressants. Combining these agents is not recommended unless there are other options. Limit the amount and duration of each drug when combined.
  Strong CYP3A4 inhibitors	Might decrease metabolism of CYP3A4 substrates (High Risk with Inhibitors).
  Droperidol	CNS Depressants may cause an increase in CNS depression. Management: Consider dose reductions of droperidol or of other CNS agents (eg, opioids, barbiturates) with concomitant use. Separate drug interaction monographs provide more detail on exceptions to this monograph.
  Erythromycin (Systemic)	May increase the serum concentration of Alfentanil. Management: For patients who are actively receiving erythromycin, caution should be used in administering alfentanil; monitor for increased anesthetic and respiratory depressant effects. You might consider using a lower dose of alfentanil, or another anesthetic.
  Fluconazole	It may increase serum levels of Alfentanil. Monitoring: Watch out for an increased respiratory depressant and anesthetic effects when alfentanil has been combined with fluconazole. You may consider using a lower initial dose of alfentanil, or another anesthetic.
  Flunitrazepam	CNS Depressants can increase the CNS depressant effects of Flunitrazepam.
  HYDROcodone	CNS Depressants can increase the CNS depressant effects of HYDROcodone. When possible, avoid concomitant use with hydrocodone, benzodiazepines, or other CNS depressionants. Combining these agents is not recommended unless there are other options. Limit the amount and duration of each drug when combined.
  Methotrimeprazine	CNS Depressants may enhance the CNS depressant effect of Methotrimeprazine. CNS Depressants may have a greater effect on the CNS if Methotrimeprazine is used. Management: Lower the adult dose of CNS Depressants by 50% and start concomitant methotrimeprazine treatment. After clinically proven efficacy of methotrimeprazine, further CNS depressant dose adjustments should only be made.
  MiFEPRIStone	High risk of Inhibitors causing an increase in serum concentrations of CYP3A4 substrates. Management: Minimize doses of CYP3A4 substrates, and monitor for increased concentrations/toxicity, during and 2 weeks following treatment with mifepristone. Avoid dihydroergotamine and ergotamine.
  Nalmefene	This may reduce the therapeutic effects of Opioid Agonists. Management: Avoid concomitant opioid agonists and nalmefene use. Stop using nalmefene one week before any planned use of opioid agonistss. Combinations of opioid agonists may require higher doses.
  Naltrexone	This may reduce the therapeutic effects of Opioid Agonists. Management: Look for alternatives to opioids. For more information, see the full drug interaction monograph.
  Ombitasvir and Ritonavir are the three main components of Ombitasvir.	It may increase the serum level of Alfentanil. If these agents are used together, be aware of the potential for alfentanil's increased anesthetic or respiratory depressant effects. You may want to use a lower dose of alfentanil, or another anesthetic. This combination is not recommended by Canadian labeling.
  Opioid Agonists	CNS Depressants can increase the CNS depressant effects of Opioid Aggonists. Management: When possible, avoid concomitant use opioid agonists and other CNS depressants. Combining these agents is not recommended unless there are other options. Limit the amount and duration of each drug when combined.
  OxyCODONE	CNS Depressants may enhance the CNS depressant effect of OxyCODONE. When possible, avoid the simultaneous use of oxycodone with benzodiazepines and other CNS depressants. Combining these agents is not recommended unless there are other options. Limit the amount and duration of each drug when combined.
  Perampanel	CNS Depressants may increase the depressant effects. Management: Patients taking perampanel with any other drug that has CNS depressant activities should avoid complex and high-risk activities, particularly those such as driving that require alertness and coordination, until they have experience using the combination.
  Rifamycin Derivatives	It may cause a decrease in serum Alfentanil concentration. Monitoring: Reduced effectiveness of alfentanil should be closely monitored. It is likely that you will need to increase your alfentanil dosage. Alternatively, changing from alfentanil to a different opioid anesthetic (e.g., sufentanil) may also be considered.
  Sincalide	Drugs that Affect Gallbladder Function may diminish the therapeutic effect of Sincalide. Management: Before using sincalide to stimulate the gallbladder, discontinue any drugs that affect gallbladder motility.
  Sodium Oxybate	CNS Depressants may have a greater depressant effect if taken in combination. Management: Look for alternatives to the combination use. If you must combine use, reduce the doses of any one or more drugs. It is not recommended to combine sodium oxybate and alcohol, or any sedative hypnotics.
  Stiripentol	High risk with inhibitors may cause an increase in serum concentration of CYP3A4 substrates. Management: Use of stiripentol with CYP3A4 substrates that are considered to have a narrow therapeutic index should be avoided due to the increased risk for adverse effects and toxicity. Monitoring of any CYP3A4 substrate that is used with stiripentol should be closely done.
  Suvorexant	CNS Depressants may enhance the CNS depressant effect of Suvorexant. Management: Suvorexant or any other CNS depressionant can be reduced. Suvorexant should not be taken with alcohol. It is also not recommended to take suvorexant along with any other drugs for insomnia.
  Tapentadol	CNS Depressants may increase the CNS depressant effects. Management: Avoid concomitant use of tapentadol and benzodiazepines or other CNS depressants when possible. If other treatment options are not available, these agents should not be combined. Limit the amount and duration of each drug when combined.
  Zolpidem	CNS Depressants may enhance the CNS depressant effect of Zolpidem. Management: For men who also take other CNS depressants, reduce the adult Intermezzo brand sublingual dose of zolpidem to 1.75mg. For women, no dose adjustment is advised. Avoid using CNS depressants at night; do not use alcohol.
  Risk Factor X (Avoid Combination)
  Azelastine (Nasal)	CNS Depressants could increase the CNS depressant effects of Azelastine.
  Bromperidol	CNS Depressants may increase the CNS depressant effects.
  Conivaptan	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Crizotinib	Might increase serum Alfentanil concentrations.
  Eluxadoline	Opioid Agonists may enhance the constipating effect of Eluxadoline.
  Enzalutamide	Might decrease serum Alfentanil concentrations.
  Fusidic Acid (Systemic).	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Idelalisib	High risk of Inhibitors causing an increase in serum CYP3A4 Substrates concentrations
  Opioids (Mixed Antagonist / Agonist)	This may reduce the analgesic effects of Opioid Agonists. Management: If patients are receiving pure opioid agonists, seek alternatives to mixed agonist/antagonist painkillers. Monitor for signs of withdrawal or therapeutic failure in patients who have received these combinations.
  Orphenadrine	Orphenadrine may be more effective against CNS depression than other drugs.
  Oxomemazine	CNS Depressants may increase the CNS depressant effects.
  Paraldehyde	Paraldehyde may be enhanced by CNS depressants.
  Thalidomide	CNS Depressants can increase Thalidomide's CNS depressant effects.

 Monitor the patient for respiratory depression, cardiovascular status, blood pressure, and heart rate. Monitoring should continue even after the procedure because of the delayed effects. Administer slowly via a continuous infusion over 3 -5 minutes. It should be administerd very slowly in young children.

Mechanism of action of Alfentanil:

Alfentanil, an opioid analgesic with a short-acting duration, binds to its receptors. The onset of action is rapid (within 5 minutes). Duration of action is dose dependent but varies between 30 to 60 minutes Protein binding is 67% to 98% Metabolism is via the liver Half-life elimination in premature newborns is up to 9 hours, and in children and adults, it varies between 40 to 111 minutes. Urine is the major route of excretion.

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