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Infergen Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP
Infergen (interferon alfacon-1) is used to treat chronic hepatitis C. It is made from human proteins. Common side effects include mood changes, feeling irritable, nervous, or anxious, headache, tired feeling, numbness, tingling, pain in hands or feet, joint or muscle pain, back pain, stomach pain or nausea, diarrhea, weight loss or thinning hair.
The recommended dose of Infergen when used alone is 15 mcg administered three times a week as a single subcutaneous injection for up to 48 weeks. Infergen may interact with drugs that weaken your immune system, such as: cancer medicine, steroids, medicines used to prevent organ transplant rejection, or medicines to treat autoimmune disorders such as arthritis, psoriasis, ulcerative colitis, or Crohn's disease. Tell your doctor all medications and supplements you use. During pregnancy, Infergen should be used only if prescribed. Infergen is sometimes used together with another drug called ribavirin. Ribavirin can cause birth defects or death in a fetus. Consult your doctor for details if you are taking ribavirin along with Infergen. It is unknown if this drug passes into breast milk or if it could harm a nursing baby. Consult your doctor before breastfeeding.
Our Infergen (interferon alfacon-1) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Infergen in Detail - Patient Information: Side Effects
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 heartbeats;
- increased urination, pain or burning when you urinate;
- bloody diarrhea;
- cough with yellow or green mucus, feeling short of breath;
- chest pain, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;
- sudden numbness or weakness, headache, confusion, or problems with vision, speech, or balance;
- worsening liver symptoms such as severe stomach pain, jaundice (yellowing of the skin or eyes);
- pancreatitis (severe pain in your upper stomach spreading to your back, nausea and vomiting, fast heart rate);
- thyroid problems (trouble concentrating, feeling too hot or cold, weight changes); or
- high blood sugar (increased thirst, fruity breath odor, increased urination, drowsiness, dry skin, nausea, and vomiting).
Less serious side effects may include:
- mood changes, feeling irritable, nervous, or anxious;
- mild headache, tired feeling;
- numbness, tingling, or pain in your hands or feet;
- joint or muscle pain, back pain;
- mild stomach pain or nausea, diarrhea; or
- weight loss or thinning hair.
Read the entire detailed patient monograph for Infergen (Interferon Alfacon-1)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Infergen FDA Prescribing Information: Side Effects
Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.
During clinical development, more than 560 subjects were exposed to 9 mcg or 15 mcg of INFERGEN monotherapy administered three times per week over a range of 24 to 48 weeks, and more than 480 subjects were exposed to 9 mcg or 15 mcg of INFERGEN, in combination with ribavirin, administered daily up to 48 weeks.
INFERGEN Monotherapy Clinical Trials
Adverse reactions that were reported, regardless of attribution to treatment, in ≥ 10% of subjects in INFERGEN monotherapy studies are presented in Table 4.
Flu-like symptoms (i.e., headache, fatigue, fever, rigors, myalgia, arthralgia, and sweating increased) were the most frequently reported treatment-related adverse reactions. In most cases, these events could be treated symptomatically.
Depression of any severity was reported in 26% of subjects who received 9 mcg INFERGEN monotherapy and was the most common adverse reaction resulting in study drug discontinuation.
INFERGEN 15 mcg three times a week monotherapy as subsequent treatment was associated with a greater incidence of leukopenia and granulocytopenia. One or more dose reductions for any causes were required in up to 36% of subjects.
Table 4: Treatment Emergent Adverse Reactions
Occurring in ≥ 10% of Subjects in INFERGEN Monotherapy Trials
|Initial Treatment||Subsequent Treatment|
|INFERGEN 9 mcg
(n = 231)
(n = 236)
|INFERGEN 15 mcg 24 wks
(n = 165)
|INFERGEN 15 mcg 48 wks
(n = 168)
|Body System/Preferred Term (COSTART)||% of Subjects||% of Subjects|
|Injection Site Erythema||23||15||17||22|
|BODY AS A WHOLE|
|SKIN AND APPENDAGES|
Combination Treatment with INFERGEN/Ribavirin Clinical Trials
The most common adverse reactions in the combination treatment with INFERGEN/ribavirin trial are listed in Table 5 and included fatigue (76%), nausea (45%), flu-like symptoms (40%), headache (42%), arthralgia (31%), and myalgia (29%), neutropenia (40%), leukopenia (29%), insomnia (39%), and depression (26%).
Adverse reactions led to early study discontinuation in 104 (21%) of subjects; more subjects discontinued from the 15 mcg INFERGEN group (64 versus 40). Fatigue, anemia, and depression were the most common adverse reactions resulting in study drug discontinuation. A higher proportion of subjects who received the recommended starting dose of 15 mcg (52%) than the 9 mcg dose group (40%) required INFERGEN dose modifications due to adverse reactions, primarily due to neutropenia/leukopenia, thrombocytopenia, and fatigue/weakness. A total of 14% of subjects experienced serious adverse reactions, the most common of which were neutropenia (2%), suicidal ideation (1%), and hyperuricemia (1%).
Table 5: Treatment Emergent Adverse Reactions
Occurring in the > 10% of Subjects in Combination Treatment with
INFERGEN/Ribavirin Phase 3 Trial
|INFERGEN 9 mcg/RBV 48 wks
(n = 244)
|INFERGEN 15 mcg/RBV 48 wks
(n = 242)
|Body System/Preferred Term (MedDRA)||% of Subjects|
|GENERAL DISORDERS and ADMINISTRATION SITE CONDITIONS (or BODY AS A WHOLE)|
|Influenza-like Illness (or Symptoms)||40||42|
|Injection Site Erythema||16||16|
|Injection Site Reaction||15||12|
|Pyrexia (or Fever)||13||17|
|METABOLISM and NUTRITION DISORDERS|
|MUSCULOSKELETAL and CONNECTIVE TISSUE DISORDERS|
|NERVOUS SYSTEM DISORDERS|
|RESPIRATORY, THORACIC, and MEDIASTINAL DISORDERS|
|SKIN and SUBCUTANEOUS TISSUE DISORDERS|
Hemoglobin and Hematocrit: Treatment with INFERGEN alone and in combination with ribavirin is associated with decreases in mean values for hemoglobin and hematocrit. In the INFERGEN monotherapy trials, 4% and 5% of subjects had decreases in hemoglobin and hematocrit levels. Decreases from baseline of 20% or more in hemoglobin or hematocrit were seen in ≤ 1% of subjects.
In the combination INFERGEN/ribavirin trial, 88% of subjects had decreases in hemoglobin levels of ≥ 2 g/dL from baseline. Of these, 27% had hemoglobin levels decrease to ≤ 10 g/dL, and underwent dose reductions of ribavirin. Anemia or hemolytic anemia led to study drug discontinuation in 10 subjects.
White Blood Cells: INFERGEN treatment is associated with decreases in mean values for both total white blood cell (WBC) count and ANC. By the end of initial monotherapy treatment, mean decreases from baseline of 19% for WBCs and 23% for ANC were observed. These effects reversed during the post treatment observation period. In two INFERGEN-monotherapy treated subjects ANC levels decreased to below 500 × 106 cells/L. In both cases, the ANC values returned to clinically acceptable levels with INFERGEN dose reductions and were not associated with infections.
Mean decreases from baseline up to 23% for WBCs and up to 27% for ANC were observed for subjects subsequently retreated with INFERGEN monotherapy. Two subjects experienced reversible reductions in ANC to less than 500 × 106 cells/L.
In the combination INFERGEN/ribavirin trial, leukopenia was reported in 24% and 34% of 9 mcg and 15 mcg treated subjects, respectively. More subjects treated with 15 mcg experienced lymphopenia than did those treated with 9 mcg: 14% versus 7%. ANC levels < 0.75 x 109/L were observed in 21% of subjects treated with 9 mcg and 27% of those treated with 15 mcg; no subjects experienced significant infections associated with low ANC levels.
Platelets: INFERGEN treatment is associated with alterations in platelet count. Decreases in mean platelet count of 16% compared to baseline were seen by the end of INFERGEN monotherapy treatment. These decreases were reversed during the post treatment observation period. Three percent of subjects had platelets decrease to less than 50 × 109 cells/L, which necessitated dose reduction.
More subjects treated with 15 mcg in the INFERGEN/ribavirin combination trial experienced a decrease in platelet counts < 40 × 109/L, 3% versus 1% in the 9 mcg dose group. None of the subjects had platelet counts < 25 × 109/L. One subject in the 15 mcg group had Grade 4 thrombocytopenia 127 days after the start of treatment, was hospitalized for this event, and treatment with both study drugs was discontinued; the event resolved 8 days later.
Triglycerides: Mean values for serum triglyceride increased shortly after the start of administration of INFERGEN monotherapy, with increases of 41%, compared with baseline, at the end of the treatment period. Seven percent of the subjects developed values which were at least 3 times above pretreatment levels during treatment. This effect was reversed after discontinuation of treatment.
In the INFERGEN/ribavirin combination trial, 7% of subjects in the 15 mcg dose group experienced increases in triglyceride levels over baseline levels at week 48 compared to 2% in the 9 mcg dose group. There were no differences in the proportion of subjects who had ≥ Grade 3 triglyceride elevations: 2% in both dose groups.
Thyroid Function: INFERGEN monotherapy treatment was associated with biochemical changes consistent with hypothyroidism including increases in TSH and decreases in T4 mean values. Increases in TSH to greater than 7 mU/L were seen in 10% of 9 mcg INFERGEN-treated subjects either during the treatment period or the 24-week post treatment observation period. Thyroid supplements were instituted in approximately one-third of these subjects.
In the combination INFERGEN/Ribavirin trial, mean increases in TSH levels from baseline were greater for the 15 mcg group compared with the 9 mcg group; 14% and 3%, respectively, at Week 12 and 54% and 0% at Week 48. No serious adverse events, discontinuations or dose modifications were related to abnormalities in thyroid function.
Uric Acid: Grade 4 ( > 10 mg/dL) uric acid levels were commonly observed in both INFERGEN/ribavirin treatment groups: 23 in the 9 mcg and 26 in the 15 mcg group. One subject in the 9 mcg group and three in the 15 mcg group experienced serious adverse events related to elevated uric acid levels. Four subjects in the 15 mcg had INFERGEN/ribavirin temporarily interrupted due to elevated uric acid levels.
The number of subjects developing positive binding antibody responses was similar in the 9 mcg INFERGEN (11%) and 3 MIU IFN α-2b groups (15%) in monotherapy studies. The titer of neutralizing antibodies to interferon was not measured. Following cessation of interferon therapy, the number of subjects with a positive antibody response declined.
In the INFERGEN/ribavirin combination study, approximately 13% of subjects in the 15 mcg and 18% in the 9 mcg arms developed low-titer neutralizing antibodies to INFERGEN. The clinical and pathological significance of the appearance of serum neutralizing antibodies is unknown. No apparent correlation of antibody development to clinical response was observed. The incidence of binding antibody was approximately 31%.
The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies for INFERGEN with the incidence of antibodies to other products may be misleading.
The following adverse reactions have been identified and reported during post-approval use of INFERGEN. Because these reactions are reported voluntarily and from a population of uncertain size, it is not possible to reliably estimate the frequency of the reaction or establish a causal relationship to drug exposure.
injection site reaction, including injection site necrosis ulcer, and bruising
Ear and Labyrinth
hearing loss, hearing impairment
Metabolism and Nutritional
Skin and Subcutaneous
bruising, pyoderma gangrenosum, toxic epidermal necrolysis
Read the entire FDA prescribing information for Infergen (Interferon Alfacon-1)
Additional Infergen Information
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