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Efgartigimod alfa Side Effects

Medically reviewed by Last updated on Aug 20, 2023.

Applies to efgartigimod alfa: intravenous solution.

Serious side effects of Efgartigimod alfa

Along with its needed effects, efgartigimod alfa 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 efgartigimod alfa:

More common

  • Bladder pain
  • bloody or cloudy urine
  • cough
  • difficult, burning, or painful urination
  • difficulty in moving
  • fever
  • frequent urge to urinate
  • joint pain
  • lower back or side pain
  • muscle aches, cramps, pain, or stiffness
  • sneezing
  • sore throat
  • swollen joints

Incidence not known

  • Difficulty in breathing or swallowing
  • fast heartbeat
  • large, hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • skin itching, rash, or redness
  • swelling of the face, throat, or tongue
  • trouble breathing

Other side effects of Efgartigimod alfa

Some side effects of efgartigimod alfa 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

  • Burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • headache

For Healthcare Professionals

Applies to efgartigimod alfa: intravenous solution.


The most common adverse reactions reported have included respiratory tract infections, headaches, and urinary tract infections.[Ref]


Very common (10% or more): Respiratory tract infections (33%)

In clinical trials, 33% of patients treated with this drug experienced respiratory tract infections compared to 29% of placebo patients.

Nervous system

Very common (10% or more): Headache (32%; included migraine, procedural headache)

Common (1% to 10%): Paraesthesia (included oral hypoesthesia, hypoesthesia, hyperesthesia)


Very common (10% or more): Drug antibodies (20%)

Common (1% to 10%): Neutralizing antibodies


Very common (10% or more): Below normal WBC counts (12%), below normal lymphocytes (28%), and below normal neutrophils (13%)

Below normal levels of WBCs, lymphocytes, and neutrophils were observed in patients treated with this drug (12%, 28%, and 13%, respectively) compared with placebo (5%, 19%, and 6%, respectively).


Very common (10% or more): Urinary tract infections (UTI; 10%)

In clinical trials, 10% of patients treated with this drug experienced UTI compared to 5% of placebo patients.


Frequency not reported: Hypersensitivity reactions including rash, angioedema, and dyspnea


Common (1% to 10%): Myalgia


1. Product Information. Vyvgart (efgartigimod alfa). argenx US Inc. 2022.

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.