Skip to main content

Alfenta Side Effects

Generic name: alfentanil

Medically reviewed by Last updated on Mar 1, 2023.

Note: This document contains side effect information about alfentanil. Some dosage forms listed on this page may not apply to the brand name Alfenta.

Applies to alfentanil: intravenous solution.


Intravenous route (Solution)

Alfentanil HCl injection exposes users to risks of addiction, abuse, and misuse, which can lead to overdose and death. Assess patient’s risk before prescribing and monitor regularly for these behaviors and conditions.

Serious side effects of Alfenta

Along with its needed effects, alfentanil (the active ingredient contained in Alfenta) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking alfentanil:

More common

  • Blurred vision
  • chest pain or discomfort
  • confusion
  • difficult or troubled breathing
  • dizziness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fainting
  • fast, slow, pounding, or irregular heartbeat or pulse
  • headache
  • irregular, fast or slow, or shallow breathing
  • lightheadedness, dizziness, or fainting
  • nervousness
  • not breathing
  • pale or blue lips, fingernails, or skin
  • pounding in the ears
  • sweating
  • trouble breathing
  • unusual tiredness or weakness


  • Cough
  • noisy breathing
  • rigid muscles of the neck, arms, and legs
  • tightness in the chest

Incidence not known

  • Agitation
  • cough
  • darkening of the skin
  • diarrhea
  • difficulty with swallowing
  • fainting
  • fever
  • hives, itching, or skin rash
  • loss of appetite
  • nausea
  • overactive reflexes
  • poor coordination
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • restlessness
  • shivering
  • sweating
  • talking or acting with excitement you cannot control
  • trembling or shaking
  • twitching
  • vomiting

Other side effects of Alfenta

Some side effects of alfentanil may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Drowsiness
  • sleepiness


  • False or unusual sense of well-being

For Healthcare Professionals

Applies to alfentanil: injectable solution.


The most commonly reported adverse reactions include apnea, rigidity, and bradycardia.[Ref]


Common (1% to 10%): Apnea

Uncommon (0.1% to 1%): Hypercarbia, laryngospasm

Frequency not reported: Life-threatening respiratory depression, postoperative respiratory depression, bronchospasm, hypoxia, bradypnea, hiccups, hypercapnia, epistaxis, airway complication of anesthesia, endotracheal intubation complication

Postmarketing reports: Respiratory arrest, cough[Ref]


Postmarketing reports: Anaphylaxis[Ref]


Very common (10% or more): Arrhythmia, bradycardia (14%), hypertension (18%), hypotension (18%), tachycardia (12%)

Frequency not reported: Asystole

Postmarketing reports: Cardiac arrest[Ref]


Very common (10% or more): Chest wall rigidity (17%),

Common (1% to 10%): Skeletal muscle movements, muscle rigidity

Uncommon (0.1% to 1%): Skeletal muscle rigidity of neck and extremities[Ref]

Nervous system

Common (1% to 10%): Dizziness, movement disorders, dyskinesia

Uncommon (0.1% to 1%): Headache

Frequency not reported: Serotonin syndrome, seizures, sleepiness/postoperative sedation, somnolence, neurological anesthetic complication

Postmarketing reports: Myoclonic movements[Ref]


Common (1% to 10%): Euphoric mood

Uncommon (0.1% to 1%): Postoperative confusion, postoperative euphoria, excitation

Frequency not reported: Addiction abuse, misuse, agitation, crying

Postmarketing reports: Disorientation[Ref]


Very common (10% or more): Nausea (28%), vomiting (18%)[Ref]


Uncommon (0.1% to 1%): Itching, urticaria

Frequency not reported: Pruritus, allergic dermatitis, hyperhidrosis

Postmarketing reports: Erythema, rash[Ref]


Common (1% to 10%): Injection site pain[Ref]



Postmarketing reports: Adrenal insufficiency, androgen deficiency[Ref]

Adrenal insufficiency has been reported with opioid use, more often following greater than 1 month of use. Androgen deficiency has occurred with chronic use of opioids.[Ref]


Uncommon (0.1% to 1%): Urinary retention[Ref]


Common (1% to 10%): Visual disturbance

Frequency not reported: Blurred vision

Postmarketing reports: Miosis[Ref]


Common (1% to 10%): Fatigue, chills

Uncommon (0.1% to 1%): Shivering

Postmarketing reports: Pyrexia[Ref]


1. Cerner Multum, Inc. UK Summary of Product Characteristics.

2. Cerner Multum, Inc. Australian Product Information.

3. Product Information. Alfentanil Hydrochloride (alfentanil). Akorn Inc. 2017.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.