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Pegasys Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP
Pegasys (peginterferon alfa-2a) is made from human proteins that help the body fight viral infections used to treat chronic hepatitis B or C. Pegasys is often used together with another medication called ribavirin (Copegus, Rebetol, RibaPak, Ribasphere, RibaTab). Common side effects of Pegasys include flu-like symptoms (fever, chills, feeling very hot or very cold, muscle aches, fatigue, headache, muscle or joint pain, nausea, vomiting, stomach pain, cough), dry mouth, loss of appetite, weight loss, trouble sleeping (insomnia), diarrhea, dry skin, temporary hair loss, skin rash, or injection site reactions (redness, swelling, itching, or dryness).
The recommended dose of Pegasys for chronic hepatitis C is 180 meg (1.0 mL vial or 0.5 mL prefilled syringe) once weekly for 48 weeks. Pegasys may interact with theophylline, methadone, or HIV or AIDS medications. Many other drugs can interact with Pegasys. Tell your doctor all prescription and over-the-counter medications and supplements you use. Pegasys is not recommended for use during pregnancy because of possible serious harm to the fetus. It is recommended that men and women use birth control while being treated with this medication and for 6 months after treatment has stopped. If you become pregnant or think you may be pregnant, inform your doctor. It is unknown if this drug passes into breast milk. Consult your doctor before breast-feeding.
Our Pegasys (peginterferon alfa-2a) 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.
Pegasys 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 this medication and call your doctor at once if you have a serious side effect such as:
- confusion, severe depression, thoughts of hurting yourself or others;
- unusual thoughts or behaviors, feeling anxious or aggressive;
- sudden weakness, loss of balance or coordination, or problems with speech;
- chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;
- numbness, burning, pain, or tingly feeling;
- fever, chills, body aches, flu symptoms;
- easy bruising or bleeding, feeling very tired;
- sores in your mouth, nose or eyes;
- redness, crusting, or drainage in your eyes;
- worsening of psoriasis;
- cough, stabbing chest pain, feeling short of breath;
- severe pain in your upper stomach spreading to your back, fast heart rate;
- high blood sugar (increased thirst, increased urination, hunger, dry mouth, fruity breath odor, drowsiness, dry skin, blurred vision, weight loss);
- low blood sugar (headache, hunger, weakness, sweating, tremors, irritability, trouble concentrating);
- vision changes, headache or pain behind your eyes; or
- fever with severe stomach pain and bloody diarrhea.
Less serious side effects may include:
- vomiting, upset stomach, loss of appetite, mild diarrhea;
- weight changes, feeling very hot or cold;
- headache, muscle or joint pain;
- sleep problems (insomnia);
- temporary hair loss, mild skin rash; or
- itching, redness, dryness, or swelling where the medicine was injected.
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.
Read the entire detailed patient monograph for Pegasys (Peginterferon alfa-2a)
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Pegasys Overview - Patient Information: Side Effects
Flu-like symptoms (e.g., fever, chills, muscle aches, fatigue, headache, joint pain, nausea, stomach pain, cough) may occur. If instructed to do so, you may take pain/fever-reducing medications (e.g., acetaminophen, ibuprofen) to help with these symptoms. Dry mouth, loss of appetite, weight loss, trouble sleeping, diarrhea, dry skin, or redness/swelling at the injection site may also occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.
Tooth and gum problems may sometimes occur during treatment. Having a dry mouth can worsen this side effect. Prevent dry mouth by drinking plenty of water or using a saliva substitute. Brush your teeth well at least twice a day and have regular dental exams. If you experience vomiting during treatment, rinse your mouth afterwards to lessen the chance of tooth and gum problems.
Temporary hair loss may occur. Normal hair growth should return after treatment has ended.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor right away if you have any serious side effects, including: persistent sore throat or fever, easy or unusual bleeding/bruising, unusually severe fatigue, unusually slow/fast/pounding heartbeat, severe stomach pain with nausea/vomiting, black/tarry stools, vomit that looks like coffee grounds, yellowing eyes or skin, dark urine, increased thirst/urination, bloody diarrhea, numbness/tingling of arms/legs.
Get medical help right away if you have any very serious side effects, including: chest pain, vision changes (such as blurred vision, partial loss of vision), seizures, slurred speech, weakness on one side of the body.
This drug may cause you to develop serious mental/mood changes that may get worse during treatment or after your last dose. Tell your doctor right away if you have symptoms such as confusion, depression, suicidal thoughts, unusual irritability, or aggressive behavior. If this occurs, psychiatric therapy and monitoring is recommended during and after treatment with this medication.
A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Pegasys (Peginterferon alfa-2a)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Pegasys FDA Prescribing Information: Side Effects
In clinical trials, a broad variety of serious adverse reactions were observed in 1,010 subjects who received PEGASYS at doses of 180 mcg for 48 weeks, alone or in combination with COPEGUS®[see BOXED WARNING and WARNINGS AND PRECAUTIONS]. The most common life-threatening or fatal events induced or aggravated by PEGASYS and COPEGUS include depression, suicide, relapse of drug abuse/overdose, and bacterial infections, each occurring at a frequency of less than 1%. Hepatic decompensation occurred in 2% (10/574) of CHC/HIV subjects [see WARNINGS AND PRECAUTIONS].
Clinical Trials Experience
Because clinical trials are conducted under widely varying and controlled conditions, adverse reaction rates observed in 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.
In all hepatitis C studies, one or more serious adverse reactions occurred in 10% of CHC monoinfected subjects and in 19% of CHC/HIV subjects receiving PEGASYS alone or in combination with COPEGUS. The most common serious adverse reactions (3% in CHC and 5% in CHC/HIV) was bacterial infection (e.g., sepsis, osteomyelitis, endocarditis, pyelonephritis, pneumonia). Other SAEs occurred at a frequency of less than 1% and included: suicide, suicidal ideation, aggression, anxiety, drug abuse and drug overdose, angina, hepatic dysfunction, fatty liver, cholangitis, arrhythmia, diabetes mellitus, autoimmune phenomena (e.g., hyperthyroidism, hypothyroidism, sarcoidosis, systemic lupus erythematosus, rheumatoid arthritis), peripheral neuropathy, aplastic anemia, peptic ulcer, gastrointestinal bleeding, pancreatitis, colitis, corneal ulcer, pulmonary embolism, coma, myositis, cerebral hemorrhage, thrombotic thrombocytopenic purpura, psychotic disorder, and hallucination.
In clinical trials, 98 to 99 percent of subjects experienced one or more adverse reactions. For hepatitis C subjects, the most commonly reported adverse reactions were psychiatric reactions, including depression, insomnia, irritability, anxiety, and flu-like symptoms such as fatigue, pyrexia, myalgia, headache, and rigors. Other common reactions were anorexia, nausea and vomiting, diarrhea, arthralgias, injection site reactions, alopecia, and pruritus. Table 7 displays pooled rates of adverse reactions occurring in greater than 5% of subjects in the PEGASYS monotherapy and PEGASYS/COPEGUS combination therapy clinical trials.
Overall 11% of CHC monoinfected subjects receiving 48 weeks of therapy with PEGASYS either alone or in combination with COPEGUS discontinued therapy; 16% of CHC/HIV coinfected subjects discontinued therapy. The most common reasons for discontinuation of therapy were psychiatric, flu-like syndrome (e.g., lethargy, fatigue, headache), dermatologic and gastrointestinal disorders, and laboratory abnormalities (thrombocytopenia, neutropenia, and anemia).
Overall 39% of subjects with CHC or CHC/HIV required modification of PEGASYS and/or COPEGUS therapy. The most common reasons for dose modification of PEGASYS in CHC and CHC/HIV subjects was for neutropenia (20% and 27%, respectively) and thrombocytopenia (4% and 6%, respectively). The most common reason for dose modification of COPEGUS in CHC and CHC/HIV subjects was anemia (22% and 16%, respectively). PEGASYS dose was reduced in 12% of subjects receiving 1000 mg to 1200 mg COPEGUS for 48 weeks and in 7% of subjects receiving 800 mg COPEGUS for 24 weeks. COPEGUS dose was reduced in 21% of subjects receiving 1000 mg to 1200 mg COPEGUS for 48 weeks and in 12% of subjects receiving 800 mg COPEGUS for 24 weeks.
Chronic hepatitis C monoinfected subjects treated for 24 weeks with PEGASYS and 800 mg COPEGUS were observed to have lower incidence of serious adverse reactions (3% vs. 10%), Hgb less than 10 g/dL (3% vs. 15%), dose modification of PEGASYS (30% vs. 36%) and COPEGUS (19% vs. 38%) and of withdrawal from treatment (5% vs. 15%) compared to subjects treated for 48 weeks with PEGASYS and 1000 mg or 1200 mg COPEGUS. The overall incidence of adverse reactions appeared to be similar in the two treatment groups.
Table 7 : Adverse Reactions Occurring in Greater Than
or Equal to 5% of Subjects in Chronic Hepatitis C Clinical Trials (Pooled
Studies 1, 2, 3, and Study 4)
|Body System||CHC Monotherapy (Pooled Studies 1-3)||CHC Combination Therapy (Study 4)|
|PEGASYS 180 mcg 48 week†
|ROFERON-A Either 3 MIU* or 6/3 MIU* of ROFERON-A 48 week†
|PEGASYS 180 mcg + 1000 mg or 1200 mg COPEGUS 48 week**
|Intron® A + 1000 mg or 1200 mg Rebetol ® 48 week**
|Application Site Disorders|
|Injection site reaction||22||18||23||16|
|Flu-like Symptoms and Signs|
|Metabolic and Nutritional|
|Musculoskeletal, Connective Tissue and Bone|
|Dizziness (excluding vertigo)||16||12||14||14|
|Respiratory, Thoracic and Mediastinal|
|Dyspnea exertional||< 1||< 1||4||7|
|Skin and Subcutaneous Tissue|
|*An induction dose of 6 million
international units (MIU) three times a week for the first 12 weeks followed by
3 million international units three times a week for 36 weeks given
† Pooled studies 1, 2, and 3 **Study 4
‡ Severe hematologic abnormalities (lymphocyte less than 500 cells/mm³; hemoglobin less than 10 g/dL; neutrophil less than 750 cells/mm³; platelet less than 50,000 cells/mm³).
In a clinical trial with 114 pediatric subjects (5 to 17 years of age) treated with PEGASYS alone or in combination with COPEGUS, dose modifications were required in approximately one-third of subjects, most commonly for neutropenia and anemia. In general, the safety profile observed in pediatric subjects was similar to that seen in adults. In the pediatric study, the most prevalent adverse events in subjects treated with combination therapy for up to 48 weeks with PEGASYS and COPEGUS were influenza-like illness (91%), upper respiratory tract infection (60%), headache (64%), gastrointestinal disorder (56%), skin disorder (47%), and injection-site reaction (45%). Seven subjects receiving combination PEGASYS and COPEGUS treatment for 48 weeks discontinued therapy for safety reasons (depression, psychiatric evaluation abnormal, transient blindness, retinal exudates, hyperglycemia, type 1 diabetes mellitus, and anemia). Most of the adverse events reported in the study were mild or moderate in severity. Severe adverse events were reported in 2 subjects in the PEGASYS plus COPEGUS combination therapy group (hyperglycemia and cholecystectomy).
Table 8 : Percentage of Pediatric Subjects with
Adverse Reactions* During First 24 Weeks of Treatment by Treatment Group (in at
Least 10% of Subjects)
|System Organ Class||Study NV17424|
|PEGASYS 180 mcg/1.73 m² x BSA + COPEGUS 15 mg/kg
|PEGASYS 180 mcg/1.73 m² x BSA + Placebo**
|General disorders and administration site conditions|
|Influenza like illness||91||81|
|Injection site reaction||44||42|
|Nervous system disorders|
|Skin and subcutaneous tissue disorders|
|Musculoskeletal, connective tissue and bone disorders|
|Metabolism and nutrition disorders|
|*Displayed adverse drug
reactions include all grades of reported adverse clinical events considered
possibly, probably, or definitely related to study drug.
**Subjects in the PEGASYS plus placebo arm who did not achieve undetectable viral load at week 24 switched to combination treatment thereafter. Therefore, only the first 24 weeks are presented for the comparison of combination therapy with monotherapy.
In pediatric subjects randomized to combination therapy, the incidence of most adverse reactions were similar for the entire treatment period (up to 48 weeks plus 24 weeks follow-up) in comparison to the first 24 weeks, and increased only slightly for headache, gastrointestinal disorder, irritability and rash. The majority of adverse reactions occurred in the first 24 weeks of treatment.
Growth inhibition in pediatric subjects [see WARNINGS AND PRECAUTIONS].
Pediatric subjects treated with PEGASYS plus ribavirin combination therapy showed a delay in weight and height increases up to 48 weeks of therapy compared with baseline. Both weight and height for age z-scores as well as the percentiles of the normative population for subject weight and height decreased during treatment. At the end of 2 years follow-up after treatment, most subjects had returned to baseline normative curve percentiles for weight (64th mean percentile at baseline, 60th mean percentile at 2 years post-treatment) and height (54th mean percentile at baseline, 56th mean percentile at 2 years post-treatment). At the end of treatment, 43% (23 of 53) of subjects experienced a weight percentile decrease of more than 15 percentiles, and 25% (13 of 53) experienced a height percentile decrease of more than 15 percentiles on the normative growth curves. At 2 years post-treatment, 16% (6 of 38) of subjects were more than 15 percentiles below their baseline weight curve and 11% (4 of 38) were more than 15 percentiles below their baseline height curve.
Thirty-eight of the 114 subjects enrolled in the long-term follow-up study extending up to 6 years posttreatment. For most subjects, post-treatment recovery in growth at 2 years post-treatment was maintained to 6 years post-treatment.
CHC with HIV Coinfection (Adults)
The adverse reaction profile of coinfected subjects treated with PEGASYS/COPEGUS in Study 7 was generally similar to that shown for monoinfected subjects in Study 4 (Table 7). Events occurring more frequently in coinfected subjects were neutropenia (40%), anemia (14%), thrombocytopenia (8%), weight decrease (16%), and mood alteration (9%).
Chronic Hepatitis B
In clinical trials of 48 week treatment duration, the adverse reaction profile of PEGASYS in chronic hepatitis B was similar to that seen in CHC PEGASYS monotherapy use, except for exacerbations of hepatitis [see WARNINGS AND PRECAUTIONS]. Six percent of PEGASYS treated subjects in the hepatitis B studies experienced one or more serious adverse reactions.
The most common or important serious adverse reactions, all of which occurred at a frequency of less than or equal to 1%, in the hepatitis B studies were infections (sepsis, appendicitis, tuberculosis, influenza), hepatitis B flares, and thrombotic thrombocytopenic purpura.
One serious adverse reaction of anaphylactic shock occurred in a dose ranging study of 191 subjects in a subject taking a higher than the approved dose of PEGASYS.
The most commonly observed adverse reactions in the PEGASYS and lamivudine groups, respectively, were pyrexia (54% vs. 4%), headache (27% vs. 9%), fatigue (24% vs. 10%), myalgia (26% vs. 4%), alopecia (18% vs. 2%), and anorexia (16% vs. 3%).
Overall 5% of hepatitis B subjects discontinued PEGASYS therapy and 40% of subjects required modification of PEGASYS dose. The most common reason for dose modification in subjects receiving PEGASYS therapy was for laboratory abnormalities including neutropenia (20%), thrombocytopenia (13%), and ALT elevation (11%).
The laboratory test values observed in the hepatitis B trials (except where noted below) were similar to those seen in the PEGASYS monotherapy CHC trials.
In the hepatitis C studies, decreases in neutrophil count below normal were observed in 95% of all subjects treated with PEGASYS either alone or in combination with COPEGUS. Severe potentially life-threatening neutropenia (ANC less than 500 cells/mm³) occurred in 5% of CHC subjects and 12% of CHC/HIV subjects receiving PEGASYS either alone or in combination with COPEGUS. Modification of PEGASYS dose for neutropenia occurred in 17% of subjects receiving PEGASYS monotherapy and 22% of subjects receiving PEGASYS/COPEGUS combination therapy. In the CHC/HIV subjects 27% required modification of interferon dosage for neutropenia. Two percent of subjects with CHC and 10% of subjects with CHC/HIV required permanent reductions of PEGASYS dosage and less than 1% required permanent discontinuation. Median neutrophil counts return to pre-treatment levels 4 weeks after cessation of therapy [see DOSAGE AND ADMINISTRATION].
Decreases in lymphocyte count are induced by interferon alpha therapy. PEGASYS plus COPEGUS combination therapy induced decreases in median total lymphocyte counts (56% in CHC and 40% in CHC/HIV, with median decrease of 1170 cells/mm³in CHC and 800 cells/mm³in CHC/HIV). In the hepatitis C studies, lymphopenia was observed during both monotherapy (81%) and combination therapy with PEGASYS and COPEGUS (91%). Severe lymphopenia (less than 500 cells/mm³) occurred in approximately 5% of all monotherapy subjects and 14% of all combination PEGASYS and COPEGUS therapy recipients. Dose adjustments were not required by protocol. The clinical significance of the lymphopenia is not known.
In CHC with HIV coinfection, CD4 counts decreased by 29% from baseline (median decrease of 137 cells/mm³) and CD8 counts decreased by 44% from baseline (median decrease of 389 cells/mm³) in the PEGASYS plus COPEGUS combination therapy arm. Median lymphocyte CD4 and CD8 counts return to pretreatment levels after 4 to 12 weeks of the cessation of therapy. CD4% did not decrease during treatment.
In the hepatitis C studies, platelet counts decreased in 52% of CHC subjects and 51% of CHC/HIV subjects treated with PEGASYS alone (respectively median decrease of 41% and 35% from baseline), and in 33% of CHC subjects and 47% of CHC/HIV subjects receiving combination therapy with COPEGUS (median decrease of 30% from baseline). Moderate to severe thrombocytopenia (less than 50,000 cells/mm³) was observed in 4% of CHC and 8% of CHC/HIV subjects. Median platelet counts return to pre-treatment levels 4 weeks after the cessation of therapy.
In the hepatitis C studies, the hemoglobin concentration decreased below 12 g/dL in 17% (median Hgb reduction of 2.2 g/dL) of monotherapy and 52% (median Hgb reduction of 3.7 g/dL) of combination therapy subjects. Severe anemia (Hgb less than 10 g/dL) was encountered in 13% of all subjects receiving combination therapy and in 2% of CHC subjects and 8% of CHC/HIV subjects receiving PEGASYS monotherapy. Dose modification for anemia in COPEGUS recipients treated for 48 weeks occurred in 22% of CHC subjects and 16% of CHC/HIV subjects [see DOSAGE AND ADMINISTRATION].
Triglyceride levels are elevated in subjects receiving alfa interferon therapy and were elevated in the majority of subjects participating in clinical studies receiving either PEGASYS alone or in combination with COPEGUS. Random levels greater than or equal to 400 mg/dL were observed in about 20% of CHC subjects. Severe elevations of triglycerides (greater than 1000 mg/dL) occurred in 2% of CHC monoinfected subjects.
In HCV/HIV coinfected subjects, fasting levels greater than or equal to 400 mg/dL were observed in up to 36% of subjects receiving either PEGASYS alone or in combination with COPEGUS. Severe elevations of triglycerides (greater than 1000 mg/dL) occurred in 7% of coinfected subjects.
Chronic Hepatitis C
One percent of subjects in the hepatitis C trials experienced marked elevations (5-to 10-fold above the upper limit of normal) in ALT levels during treatment and follow-up. These transaminase elevations were on occasion associated with hyperbilirubinemia and were managed by dose reduction or discontinuation of study treatment. Liver function test abnormalities were generally transient. One case was attributed to autoimmune hepatitis, which persisted beyond study medication discontinuation [see DOSAGE AND ADMINISTRATION].
Chronic Hepatitis B
Transient ALT elevations are common during hepatitis B therapy with PEGASYS. Twenty-five percent and 27% of subjects experienced elevations of 5 to 10 x ULN and 12% and 18% had elevations of greater than 10 x ULN during treatment of HBeAg negative and HBeAg positive disease, respectively. Flares have been accompanied by elevations of total bilirubin and alkaline phosphatase and less commonly with prolongation of PT and reduced albumin levels. Eleven percent of subjects had dose modifications due to ALT flares and less than 1% of subjects were withdrawn from treatment [see WARNINGS AND PRECAUTIONSand DOSAGE AND ADMINISTRATION].
ALT flares of 5 to 10 x ULN occurred in 13% and 16% of subjects, while ALT flares of greater than 10 x ULN occurred in 7% and 12% of subjects in HBeAg negative and HBeAg positive disease, respectively, after discontinuation of PEGASYS therapy.
PEGASYS alone or in combination with COPEGUS was associated with the development of abnormalities in thyroid laboratory values, some with associated clinical manifestations. In the hepatitis C studies, hypothyroidism or hyperthyroidism requiring treatment, dose modification or discontinuation occurred in 4% and 1% of PEGASYS treated subjects and 4% and 2% of PEGASYS and COPEGUS treated subjects, respectively. Approximately half of the subjects, who developed thyroid abnormalities during PEGASYS treatment, still had abnormalities during the follow-up period [see WARNINGS AND PRECAUTIONS].
Decreases in hemoglobin, neutrophils and platelets may require dose reduction or permanent discontinuation from treatment [see DOSAGE AND ADMINISTRATION]. Most laboratory abnormalities noted during the clinical trial (Table 9) returned to baseline levels shortly after completion of treatment.
Table 9 : Selected Hematologic Abnormalities During
First 24 Weeks of Treatment by Treatment Group in Previously Untreated
|Laboratory Parameter||PEGASYS 180 mcg/1.73 m² x BSA + COPEGUS 15 mg/kg
|PEGASYS 180 mcg/1.73 m² x BSA + Placebo*
|1,000 - < 1,500||31%||39%|
|750 - < 1,000||27%||17%|
|500 - < 750||25%||15%|
|75,000 - < 100,000||4%||2%|
|50,000 - < 75,000||0%||2%|
|8.5- < 10||7%||3%|
|*Subjects in the PEGASYS plus placebo arm who did not achieve undetectable viral load at week 24 switched to combination treatment thereafter. Therefore, only the first 24 weeks are presented for the comparison of combination therapy with monotherapy.|
In patients randomized to combination therapy, the incidence of abnormalities during the entire treatment phase (up to 48 weeks plus 24 weeks follow-up) in comparison to the first 24 weeks increased slightly for neutrophils between 500 and 1,000 cells/mm≥ and hemoglobin values between 8.5 and 10 g/dL. The majority of hematologic abnormalities occurred in the first 24 weeks of treatment.
Chronic Hepatitis C
Nine percent (71/834) of subjects treated with PEGASYS with or without COPEGUS developed binding antibodies to interferon alfa-2a, as assessed by an ELISA assay. Three percent of subjects (25/835) receiving PEGASYS with or without COPEGUS, developed low-titer neutralizing antibodies (using an assay with a sensitivity of 100 INU/mL).
Chronic Hepatitis B
Twenty-nine percent (42/143) of hepatitis B subjects treated with PEGASYS for 24 weeks developed binding antibodies to interferon alfa-2a, as assessed by an ELISA assay. Thirteen percent of subjects (19/143) receiving PEGASYS developed low-titer neutralizing antibodies (using an assay with a sensitivity of 100 INU/mL).
The clinical and pathological significance of the appearance of serum neutralizing antibodies is unknown. No apparent correlation of antibody development to clinical response or adverse events was observed. The percentage of subjects whose test results were considered positive for antibodies is highly dependent on the sensitivity and specificity of the assays.
Additionally, the observed incidence of antibody positivity in these assays may be influenced by several factors including sample timing and handling, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies to PEGASYS 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 PEGASYS therapy. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Blood and lymphatic system disorders: pure red cell aplasia
Ear and labyrinth disorders: hearing impairment, hearing loss
Gastrointestinal disorders: tongue pigmentation
Immune system disorders: Liver graft rejection and renal graft rejection [see Use in Specific Populations]
Metabolism and nutrition disorders: dehydration
Skin and subcutaneous tissue disorders: serious skin reactions
Read the entire FDA prescribing information for Pegasys (Peginterferon alfa-2a)
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