May 27, 2017
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(interferon alfacon-1) Injection for Subcutaneous Use



Alpha interferons, including INFERGEN, cause or aggravate fatal or life-threatening neuropsychiatric, autoimmune, ischemic, and infectious disorders. Patients should be monitored closely with periodic clinical and laboratory evaluations. Patients with persistently severe or worsening symptoms of these conditions should be withdrawn from therapy. In many but not all cases, these disorders resolve after stopping interferon alfacon-1 therapy. [see WARNINGS AND PRECAUTIONS and ADVERSE REACTIONS].

Use with Ribavirin: Ribavirin may cause birth defects and/or death of the unborn child. Extreme care must be taken to avoid pregnancy in female patients and in female partners of male patients. Ribavirin causes hemolytic anemia. The anemia associated with ribavirin therapy may result in a worsening of cardiac disease. . [see WARNINGS AND PRECAUTIONS; and Ribavirin Labeling].


Interferon alfacon-1 is a wholly synthetic type-I interferon. The 166-amino acid sequence of interferon alfacon-1 was derived by scanning the sequences of several natural interferon alpha subtypes and assigning the most frequently observed amino acid in each corresponding position resulting in a consensus sequence. Four additional amino acid changes were made to facilitate the molecular construction, and a corresponding synthetic DNA sequence was constructed using chemical synthesis methodology. Interferon alfacon-1 differs from interferon alfa-2b at 19/166 amino acids (88% homology), and with Interferon alfa-2a at 18/166 amino acids (88% homology). Comparison with interferon-beta shows identity at over 30% of the amino acid positions. Interferon alfacon-1 is produced in Escherichia coli (E. coli) cells that have been genetically altered by insertion of a synthetically constructed sequence that codes for interferon alfacon-1. Prior to final purification, interferon alfacon-1 is allowed to oxidize to its native state, and its final purity is achieved by sequential passage over a series of chromatography columns. This protein has a molecular weight of 19,434 daltons.

INFERGEN is a sterile, clear, colorless, preservative-free liquid formulated with 100 mM sodium chloride and 27 mM sodium phosphate at pH 7.0 ± 0.2. The product is available in single-use vials containing 9 mcg and 15 mcg interferon alfacon-1 at a fill volume of 0.3 mL and 0.5 mL, respectively. INFERGEN vials contain 0.03 mg/mL interferon alfacon-1, sodium chloride (5.9 mg/mL), and sodium phosphate (3.8 mg/mL) in Water for Injection, USP. INFERGEN is to be administered undiluted by subcutaneous injection.

What are the possible side effects of interferon alfacon-1 (Infergen)?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using interferon alfacon-1 and call your doctor at once if you have a serious side effect such as:

  • severe depression, aggressive behavior, or thoughts of hurting yourself;
  • fever, chills, sore throat, body aches, flu symptoms;
  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum);
  • feeling like you might pass out;
  • fast, pounding, or uneven...

Read All Potential Side Effects and See Pictures of Infergen »

Last reviewed on RxList: 3/20/2017
This monograph has been modified to include the generic and brand name in many instances.

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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