RIBAVIRIN

Ribavirin, is a synthetic nucleoside analogue (purine analogue). The chemical name of ribavirin is 1-β-D-ribofuranosyl-1H-1,2,4-triazole-3-carboxamide and has the following structural formula (see Figure 1). Figure 1: Structural Formula Ribavirin USP is a white, crystalline powder. It is freely soluble in water and slightly soluble in anhydrous alcohol. The molecular formula is C 8 H 12 N 4 O 5 and the molecular weight is 244.21. Ribavirin capsules USP consist of a white to off-white granular powder in a white, opaque, gelatin capsule. Each capsule contains 200 mg ribavirin and the inactive ingredients microcrystalline cellulose, lactose monohydrate, povidone-K 30, and magnesium stearate. The capsule shell consists of titanium dioxide, sodium lauryl sulfate, and gelatin. The capsule is printed with edible ink containing black iron oxide. Meets USP dissolution test 2. Chemical Structure

Ribavirin capsules are a nucleoside analogue indicated in combination with interferon alfa-2b (pegylated and nonpegylated) for the treatment of Chronic Hepatitis C (CHC) in patients 3 years of age or older with compensated liver disease. ( 1.1 ) Patients with the following characteristics are less likely to benefit from re-treatment after failing a course of therapy: previous nonresponse, previous pegylated interferon treatment, significant bridging fibrosis or cirrhosis, and genotype 1 infection. 1.1 Chronic Hepatitis C (CHC) Ribavirin capsules in combination with interferon alfa-2b (pegylated and nonpegylated) are indicated for the treatment of Chronic Hepatitis C (CHC) in patients 3 years of age and older with compensated liver disease [see Warnings and Precautions (5.9 , 5.10) , and Use in Specific Populations (8.4) ]. The following points should be considered when initiating ribavirin capsules combination therapy with PegIntron ® or INTRON A ® : Combination therapy with ribavirin capsules/PegIntron is preferred over ribavirin capsules/INTRON A as this combination provides substantially better response rates [see Clinical Studies (14) ]. Patients with the following characteristics are less likely to benefit from re-treatment after failing a course of therapy: previous nonresponse, previous pegylated interferon treatment, significant bridging fibrosis or cirrhosis, and genotype 1 infection [see Clinical Studies (14) ]. No safety and efficacy data are available for treatment duration lasting longer than one year.

Ribavirin capsules are administered according to body weight. ( 2.1 , 2.2 , 2.3 ) Dose reduction or discontinuation is recommended in patients experiencing certain adverse reactions or renal dysfunction. ( 2.5 , 2.6 , 12.3 ) 2.1 General Dosing Information Do not open, crush or break ribavirin capsules. Ribavirin capsules should be taken with food [see Clinical Pharmacology (12.3) ]. 2.2 Ribavirin capsules/PegIntron Combination Therapy Adult Patients The recommended dose of ribavirin capsules when used in combination with PegIntron is 800 mg to 1,400 mg based on patient body weight in two divided doses (see Table 1). Refer to PegIntron labeling for PegIntron dosing information. Duration of Treatment – Interferon Alpha-naïve Patients The treatment duration for patients with genotype 1 is 48 weeks. Discontinuation of therapy should be considered in patients who do not achieve at least a 2 log 10 drop or loss of hepatitis C virus (HCV)-RNA at 12 weeks, or if HCV-RNA remains detectable after 24 weeks of therapy. Patients with genotype 2 and 3 should be treated for 24 weeks. Duration of Treatment – Re-treatment with PegIntron/Ribavirin capsules of Prior Treatment Failures The treatment duration for patients who previously failed therapy is 48 weeks, regardless of HCV genotype. Re-treated patients who fail to achieve undetectable HCV-RNA at Week 12 of therapy, or whose HCV-RNA remains detectable after 24 weeks of therapy, are highly unlikely to achieve SVR and discontinuation of therapy should be considered [see Clinical Studies (14.1) ]. Table 1: Recommended Adult Dosing for Ribavirin capsules in Combination with PegIntron Body Weight (kg) Ribavirin capsules Daily Dose Ribavirin Number of Capsules Less than 66 800 mg/day 2 x 200 mg capsules AM 2 x 200 mg capsules PM 66 to 80 1,000 mg/day 2 x 200 mg capsules AM 3 x 200 mg capsules PM 81 to 105 1,200 mg/day 3 x 200 mg capsules AM 3 x 200 mg capsules PM Greater than 105 1,400 mg/day 3 x 200 mg capsules AM 4 x 200 mg capsules PM Pediatric Patients Dosing of ribavirin in pediatric patients is determined by body weight. The recommended dose of ribavirin when used in combination with PegIntron in pediatric patients ages 3 to 17 years is 15 mg/kg/day in two divided doses (see Table 2). Refer to PegIntron labeling for PegIntron dosing information. The treatment duration for patients with genotype 1 is 48 weeks. Patients with genotype 2 and 3 should be treated for 24 weeks. Table 2: Recommended Pediatric Ribavirin Dosing in Combination with PegIntron * Ribavirin Oral Solution may be used in any patient regardless of body weight. Body Weight (kg) Ribavirin Daily Dose Ribavirin Number of Capsules Less than 47 15 mg/kg/day Use Ribavirin Oral Solution* 47 to 59 800 mg/day 2 x 200 mg capsules AM 2 x 200 mg capsules PM 60 to 73 1,000 mg/day 2 x 200 mg capsules AM 3 x 200 mg capsules PM Greater than 73 1,200 mg/day 3 x 200 mg capsules AM 3 x 200 mg capsules PM 2.3 Ribavirin capsules/INTRON A Combination Therapy Adults Duration of Treatment – Interferon Alpha-naïve Patients The recommended dose of ribavirin capsules when used in combination with INTRON A depends on the patient’s body weight (see Table 3). Refer to Intron A labeling for interferon dosing information. The recommended duration of treatment for patients previously untreated with interferon is 24 to 48 weeks. The duration of treatment should be individualized to the patient depending on baseline disease characteristics, response to therapy, and tolerability of the regimen [see Indications and Usage (1.1), Adverse Reactions (6.1) , and Clinical Studies (14) ]. After 24 weeks of treatment, virologic response should be assessed. Treatment discontinuation should be considered in any patient who has not achieved an HCV-RNA below the limit of detection of the assay by 24 weeks. There are no safety and efficacy data for treatment duration lasting longer than 48 weeks in the previously untreated patient population. Duration of Treatment – Re-treatment with INTRON A/Ribavirin capsules in Relapse Patients In patients who relapse following nonpegylated interferon monotherapy, the recommended duration of treatment is 24 weeks. Table 3: Recommended Ribavirin capsules Dosing in Combination with INTRON A Body Weight Ribavirin Capsules At least 75 kg 2 x 200 mg capsules AM 3 x 200 mg capsules PM daily orally Greater than 75 kg 3 x 200 mg capsules AM 3 x 200 mg capsules PM daily orally Pediatrics The recommended dose of ribavirin when used in combination with INTRON A is 15 mg/kg per day orally in two divided doses (see Table 2). Refer to Intron A labeling for interferon dosing information. The recommended duration of treatment is 48 weeks for pediatric patients with genotype 1. After 24 weeks of treatment, virologic response should be assessed. Treatment discontinuation should be considered in any patient who has not achieved an HCV-RNA below the limit of detection of the assay by this time. The recommended duration of treatment for pediatric patients with genotype 2 and 3 is 24 weeks. 2.4 Testing Prior to Initiation of Ribavirin capsules The following laboratory tests are recommended in all patients treated with ribavirin capsules prior to initiation of treatment and periodically thereafter. Standard hematologic tests - including hemoglobin (pretreatment, Week 2 and Week 4 of therapy, and as clinically appropriate [see Warnings and Precautions (5.2 , 5.6) ], complete and differential white blood cell counts, and platelet count. Blood chemistries - liver function tests and TSH. Pregnancy - in women of childbearing potential. ECG [see Warnings and Precautions (5.2) ]. 2.5 Dose Modifications If severe adverse reactions or laboratory abnormalities develop during ribavirin capsules combination therapy, modify or discontinue the dose until the adverse reaction abates or decreases in severity (see Table 4) [see Warnings and Precautions (5) ]. If intolerance persists after dose adjustment, combination therapy should be discontinued. Refer to PegIntron labeling for additional information regarding dose reduction of PegIntron. Dose reduction in pediatric patients is accomplished by modifying the recommended ribavirin capsules dose from the original starting dose of 15 mg/kg daily in a two-step process to 12 mg/kg/day, then to 8 mg/kg/day, if needed (see Table 4). Ribavirin capsules are contraindicated in patients with creatinine clearance less than 50 mL/min [see Contraindications (4) ] . Patients with impaired renal function and those over the age of 50 should be carefully monitored with respect to development of anemia [see Warnings and Precautions (5.2) , Use in Specific Populations (8.5) , and Clinical Pharmacology (12.3) ] . Ribavirin capsules should be administered with caution to patients with pre-existing cardiac disease. Assess cardiovascular status before initiation of treatment and during therapy. If there is any deterioration of cardiovascular status, discontinue combination therapy [see Warnings and Precautions (5.2) ]. In patients with a history of stable cardiovascular disease, a permanent dose reduction is required if the hemoglobin decreases by 2 g/dL or more during any 4-week period. If the hemoglobin level remains below 12 g/dL after 4 weeks on a reduced dose, discontinue combination therapy. Modify or discontinue ribavirin capsules dosing in any patient whose hemoglobin level falls below 10 g/dL (see Table 4) [see Warnings and Precautions (5.2) ]. Table 4: Guidelines for Dose Modification and Discontinuation of Ribavirin capsules in combination with PegIntron or INTRON A Based on Laboratory Parameters in Adults and Pediatrics Laboratory Parameters Reduce Ribavirin capsules Daily Dose (see note 1) if: Reduce PegIntron or INTRON A Dose (see note 2) if: Discontinue Therapy if: Note 1: Adult patients: 1 st dose reduction of ribavirin is by 200 mg/day (except in patients receiving the 1,400 mg, dose reduction should be by 400 mg/day). If needed, 2 nd dose reduction of ribavirin is by an additional 200 mg/day. Patients whose dose of ribavirin is reduced to 600 mg daily receive one 200 mg capsule in the morning and two 200 mg capsules in the evening. Pediatric patients: 1 st dose reduction of ribavirin is to 12 mg/kg/day, 2 nd dose reduction of ribavirin is to 8 mg/kg/day. Note 2: Adult patients treated with ribavirin capsules and PegIntron: 1 st dose reduction of PegIntron is to 1 mcg/kg/week. If needed, 2 nd dose reduction of PegIntron is to 0.5 mcg/kg/week. Pediatric patients treated with ribavirin capsules and PegIntron: 1 st dose reduction of PegIntron is to 40 mcg/m 2 /week, 2 nd dose reduction of PegIntron is to 20 mcg/m 2 /week. For patients on ribavirin capsules /INTRON A combination therapy : reduce INTRON A dose by 50%. * Pediatric patients who have pre-existing cardiac conditions and experience a hemoglobin decrease greater than or equal to 2 g/dL during any 4-week period during treatment should have weekly evaluations and hematology testing. † These guidelines are for patients with stable cardiac disease. Patients with a history of significant or unstable cardiac disease should not be treated with PegIntron/ribavirin capsules combination therapy [see Warnings and Precautions (5.2) ] . WBC N/A 1.0 to <1.5 x 10 9 /L <1.0 x 10 9 /L Neutrophils N/A 0.5 to <0.75 x 10 9 /L <0.5 x 10 9 /L Platelets N/A 25 to < 50 x 10 9 /L (adults) <25 x 10 9 /L (adults) N/A 50 to <70 x 10 9 /L (pediatrics) <50 x 10 9 /L (pediatrics) Creatinine N/A N/A >2 mg/dL (pediatrics) Hemoglobin in patients without history of cardiac disease 8.5 to <10 g/dL N/A <8.5 g/dL Reduce Ribavirin capsules Dose by 200 mg/day and PegIntron or INTRON A Dose by Half if: Hemoglobin in patients with history of stable cardiac disease *† ≥2 g/dL decrease in hemoglobin during any four-week period during treatment <8.5 g/dL or <12 g/dL after four weeks of dose reduction Refer to labeling for INTRON A or PegIntron for additional information about how to reduce an INTRON A or PegIntron dose. 2.6 Discontinuation of Dosing Adults In HCV genotype 1, interferon-alfa-naïve patients receiving PegIntron in combination with ribavirin, discontinue therapy if there is not at least a 2 log 10 drop or loss of HCV-RNA at 12 weeks of therapy, or if HCV-RNA levels remain detectable after 24 weeks of therapy. Regardless of genotype, previously treated patients who have detectable HCV-RNA at Week 12 or 24 are highly unlikely to achieve SVR and discontinuation of therapy should be considered. Pediatrics (3 to 17 years of age) In patients receiving PegIntron/ribavirin capsules combination (excluding HCV Genotype 2 and 3), discontinue therapy at 12 weeks if HCV-RNA has dropped less than 2 log 10 compared to pretreatment level, or at 24 weeks if HCV-RNA is still detectable.

Ribavirin capsules combination therapy is contraindicated in: pregnancy. Ribavirin capsules may cause fetal harm when administered to a pregnant woman. Ribavirin capsules are contraindicated in women who are pregnant or planning to become pregnant. If a patient becomes pregnant while taking ribavirin capsules, the patient should be apprised of the potential hazard to the fetus [see Warnings and Precautions (5.1) , and Use in Specific Populations (8.1, 8.3) ]. men whose female partners are pregnant [see Use in Specific Populations (8.3) ] patients with known hypersensitivity reactions such as Stevens-Johnson syndrome, toxic, epidermal necrolysis, and erythema multiforme to ribavirin or any component of the product patients with autoimmune hepatitis patients with hemoglobinopathies (e.g., thalassemia major, sickle-cell anemia) patients with creatinine clearance less than 50 mL/min [see Clinical Pharmacology (12.3) ] when coadministered with didanosine because exposure to the active metabolite of didanosine (dideoxyadenosine 5’-triphosphate) is increased. Fatal hepatic failure, as well as peripheral neuropathy, pancreatitis, and symptomatic hyperlactatemia/lactic acidosis, has been reported in patients receiving didanosine in combination with ribavirin [see Drug Interactions (7.1) ]. Pregnancy and men whose female partners are pregnant ( 4 , 5.1 , 8.1 , 8.3 ) Known hypersensitivity reactions such as Stevens-Johnson syndrome, toxic, epidermal necrolysis, and erythema multiforme to ribavirin or any component of the product ( 4 ) Autoimmune hepatitis ( 4 ) Hemoglobinopathies ( 4 ) Creatinine clearance less than 50 mL/min ( 4 , 12.3 ) Coadministration with didanosine ( 4 , 7.1 )

The following serious adverse drug reactions are discussed in other sections of the labeling: Embryo-Fetal Toxicity [see Warnings and Precautions (5.1) ] Anemia [see Warnings and Precautions (5.2) ] Pancreatitis [see Warnings and Precautions (5.3) ] Pulmonary Disorders [see Warnings and Precautions (5.4) ] Ophthalmic Disorders [see Warnings and Precautions (5.5) ] Dental and Periodontal Disorders [see Warnings and Precautions (5.7) ] Impact on Growth in Pediatric Patients [see Warnings and Precautions (5.9) ] Hemolytic anemia occurred in more than 10% of adult patients receiving ribavirin/PegIntron or INTRON A combination therapy. ( 6.1 ) Most common adverse reactions (40% or greater) in adult patients receiving ribavirin/PegIntron or INTRON A combination therapy are injection site reaction, fatigue/asthenia, headache, rigors, fevers, nausea, myalgia and anxiety/emotional lability/irritability. ( 6.1 ) Most common adverse reactions (greater than 25%) in pediatric patients receiving ribavirin/PegIntron therapy are: pyrexia, headache, neutropenia, fatigue, anorexia, injection site erythema, and vomiting. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Aurobindo Pharma USA, Inc. at 1-866-850-2876 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 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. Clinical trials with ribavirin in combination with PegIntron or INTRON A have been conducted in over 7,800 subjects from 3 to 76 years of age. The primary toxicity of ribavirin is hemolytic anemia. Reductions in hemoglobin levels occurred within the first 1 to 2 weeks of oral therapy. Cardiac and pulmonary reactions associated with anemia occurred in approximately 10% of patients [see Warnings and Precautions (5.2) ]. Greater than 96% of all subjects in clinical trials experienced one or more adverse reactions. The most commonly reported adverse reactions in adult subjects receiving PegIntron or INTRON A in combination with ribavirin were injection site inflammation/reaction, fatigue/asthenia, headache, rigors, fevers, nausea, myalgia and anxiety/emotional lability/irritability. The most common adverse reactions in pediatric subjects, ages 3 and older, receiving ribavirin in combination with PegIntron or INTRON A were pyrexia, headache, neutropenia, fatigue, anorexia, injection site erythema, and vomiting. The Adverse Reactions section references the following clinical trials: Ribavirin/PegIntron Combination therapy trials: Clinical Study 1 – evaluated PegIntron monotherapy (not further described in this label; see labeling for PegIntron for information about this trial). Study 2 – evaluated ribavirin 800 mg/day flat dose in combination with 1.5 mcg/kg/week PegIntron or with INTRON A. Study 3 – evaluated PegIntron/weight-based ribavirin in combination with PegIntron/flat dose ribavirin regimen. Study 4 – compared two PegIntron (1.5 mcg/kg/week and 1 mcg/kg/week) doses in combination with ribavirin and a third treatment group receiving Pegasys ® (180 mcg/week)/Copegus ® (1000 to 1200 mg/day). Study 5 – evaluated PegIntron (1.5 mcg/kg/week) in combination with weight-based ribavirin in prior treatment failure subjects. PegIntron/Ribavirin Combination Therapy in Pediatric Patients Ribavirin/INTRON A Combination Therapy trials for adults and pediatrics Serious adverse reactions have occurred in approximately 12% of subjects in clinical trials with PegIntron with or without ribavirin [see Boxed Warning , Warnings and Precautions (5) ]. The most common serious events occurring in subjects treated with PegIntron and ribavirin were depression and suicidal ideation [see Warnings and Precautions (5.10) ], each occurring at a frequency of less than 1%. Suicidal ideation or attempts occurred more frequently among pediatric patients, primarily adolescents, compared to adult patients (2.4% versus 1%) during treatment and off-therapy follow-up [ see Warnings and Precautions (5.10) ]. The most common fatal reaction occurring in subjects treated with PegIntron and ribavirin was cardiac arrest, suicidal ideation, and suicide attempt [see Warnings and Precautions (5.10)] , all occurring in less than 1% of subjects. Adverse Reaction - Ribavirin/PegIntron Combination Therapy Adult Subjects Adverse reactions that occurred in the clinical trial at greater than 5% incidence are provided by treatment group from the ribavirin/PegIntron Combination Therapy (Study 2) in Table 5. Table 5: Adverse Reactions Occurring in Greater Than 5% of Adult Subjects * A subject may have reported more than one adverse reaction within a body system/organ class category. Adverse Reactions Percentage of Subjects Reporting Adverse Reactions* Adverse Reactions Percentage of Subjects Reporting Adverse Reactions* PegIntron 1.5 mcg/kg/ Ribavirin (N=511) INTRON A/ Ribavirin (N=505) PegIntron 1.5 mcg/kg/ Ribavirin (N=511) INTRON A/ Ribavirin (N=505) Application Site Musculoskeletal Injection Site Inflammation Injection Site Reaction 25 58 18 36 Myalgia 56 50 Arthralgia 34 28 Autonomic Nervous System Musculoskeletal Pain 21 19 Dry Mouth 12 8 Psychiatric Increased Sweating 11 7 Insomnia 40 41 Flushing 4 3 Depression 31 34 Body as a Whole Anxiety/Emotional Lability/Irritability 47 47 Fatigue/Asthenia 66 63 Concentration Impaired 17 21 Headache 62 58 Agitation 8 5 Rigors 48 41 Nervousness 6 6 Fever 46 33 Reproductive, Female Weight Loss 29 20 Menstrual Disorder 7 6 Right Upper Quadrant Pain 12 6 Resistance Mechanism Chest Pain 8 7 Viral Infection 12 12 Malaise 4 6 Fungal Infection 6 1 Central/Peripheral Nervous System Respiratory System Dizziness 21 17 Dyspnea 26 24 Endocrine Coughing 23 16 Hypothyroidism 5 4 Pharyngitis 12 13 Gastrointestinal Rhinitis 8 6 Nausea 43 33 Sinusitis 6 5 Anorexia 32 27 Skin and Appendages Diarrhea 22 17 Alopecia 36 32 Vomiting 14 12 Pruritus 29 28 Abdominal Pain 13 13 Rash 24 23 Dyspepsia 9 8 Skin Dry 24 23 Constipation 5 5 Special Senses, Other Hematologic Disorders Taste Perversion 9 4 Neutropenia 26 14 Vision Disorders Anemia 12 17 Vision Blurred 5 6 Leukopenia 6 5 Conjunctivitis 4 5 Thrombocytopenia 5 2 Liver and Biliary System Hepatomegaly 4 4 Table 6 summarizes the treatment-related adverse reactions in Study 4 that occurred at a greater than or equal to 10% incidence. Table 6: Treatment-Related Adverse Reactions (Greater Than or Equal to 10% Incidence) By Descending Frequency Study 4 Percentage of Subjects Reporting Treatment-Related Adverse Reactions Adverse Reactions PegIntron 1.5 mcg/kg with Ribavirin (N=1019) PegIntron 1 mcg/kg with Ribavirin (N=1016) Pegasys 180 mcg with Copegus (N=1035) Fatigue 67 68 64 Headache 50 47 41 Nausea 40 35 34 Chills 39 36 23 Insomnia 38 37 41 Anemia 35 30 34 Pyrexia 35 32 21 Injection Site Reactions 34 35 23 Anorexia 29 25 21 Rash 29 25 34 Myalgia 27 26 22 Neutropenia 26 19 31 Irritability 25 25 25 Depression 25 19 20 Alopecia 23 20 17 Dyspnea 21 20 22 Arthralgia 21 22 22 Pruritus 18 15 19 Influenza-like Illness 16 15 15 Dizziness 16 14 13 Diarrhea 15 16 14 Cough 15 16 17 Weight Decreased 13 10 10 Vomiting 12 10 9 Unspecified Pain 12 13 9 Dry Skin 11 11 12 Anxiety 11 11 10 Abdominal Pain 10 10 10 Leukopenia 9 7 10 The incidence of serious adverse reactions was comparable in all trials. In Study 2, the incidence of serious adverse reactions was 17% in the PegIntron/ribavirin groups compared to 14% in the INTRON A/ribavirin group. In Study 3, there was a similar incidence of serious adverse reactions reported for the weight-based ribavirin group (12%) and for the flat-dose ribavirin regimen. In many but not all cases, adverse reactions resolved after dose reduction or discontinuation of therapy. Some subjects experienced ongoing or new serious adverse reactions during the 6-month follow-up period. In Study 2, many subjects continued to experience adverse reactions several months after discontinuation of therapy. By the end of the 6-month follow-up period, the incidence of ongoing adverse reactions by body class in the PegIntron 1.5/ribavirin group was 33% (psychiatric), 20% (musculoskeletal), and 10% (for endocrine and for GI). In approximately 10 to 15% of subjects, weight loss, fatigue, and headache had not resolved. There have been 28 subject deaths that occurred during treatment or follow-up in Studies 2, 3, and 4. In Study 2, there was 1 suicide in a subject receiving PegIntron/ribavirin combination therapy; and 1 subject death in the INTRON A/ribavirin group (motor vehicle accident). In Study 3, there were 14 deaths, 2 of which were probable suicides and 1 was an unexplained death in a person with a relevant medical history of depression. In Study 4, there were 12 deaths, 6 of which occurred in subjects who received PegIntron/ribavirin combination therapy, 5 in the PegIntron 1.5 mcg/ribavirin arm (N=1019) and 1 in the PegIntron 1 mcg/ribavirin arm (N=1016), and 6 of which occurred in subjects receiving Pegasys/Copegus (N=1035); there were 3 suicides that occurred during the off treatment follow-up period in subjects who received PegIntron (1.5 mcg/kg)/ribavirin combination therapy. In Studies 1 and 2, 10 to 14% of subjects receiving PegIntron, alone or in combination with ribavirin, discontinued therapy compared with 6% treated with INTRON A alone and 13% treated with INTRON A in combination with ribavirin. In Study 3, 15% of subjects receiving PegIntron in combination with weight-based ribavirin and 14% of subjects receiving PegIntron with flat-dose ribavirin discontinued therapy due to an adverse reaction. The most common reasons for discontinuation were related to known interferon effects of psychiatric, systemic (e.g., fatigue, headache), or gastrointestinal adverse reactions. In Study 4, 13% of subjects in the PegIntron 1.5 mcg/ribavirin arm, 10% in the PegIntron 1 mcg/ribavirin arm, and 13% in the Pegasys 180 mcg/Copegus arm discontinued due to adverse events. In Study 2, dose reductions for ribavirin were similar across all three groups [see Clinical Studies (14.1)] , 33 to 35%. The most common reasons for dose modifications were neutropenia (18%), or anemia (9%) (see Laboratory Values). Other common reasons included depression, fatigue, nausea, and thrombocytopenia. In Study 3, dose modifications due to adverse reactions occurred more frequently with weight-based ribavirin dosing compared to flat dosing (29% and 23%, respectively). In Study 4, 16% of subjects had a dose reduction of PegIntron to 1 mcg/kg in combination with ribavirin, with an additional 4% requiring the second dose reduction of PegIntron to 0.5 mcg/kg due to adverse events compared to 15% of subjects in the Pegasys/Copegus arm, who required a dose reduction to 135 mcg/week with Pegasys, with an additional 7% in the Pegasys/Copegus arm requiring a second dose reduction to 90 mcg/week with Pegasys. In the PegIntron/ribavirin combination trials the most common adverse reactions were psychiatric, which occurred among 77% of subjects in Study 2 and 68% to 69% of subjects in Study 3. These psychiatric adverse reactions included most commonly depression, irritability, and insomnia, each reported by approximately 30% to 40% of subjects in all treatment groups. Suicidal behavior (ideation, attempts, and suicides) occurred in 2% of all subjects during treatment or during follow-up after treatment cessation [see Warnings and Precautions (5) ] . In Study 4, psychiatric adverse reactions occurred in 58% of subjects in the PegIntron 1.5 mcg/ribavirin arm, 55% of subjects in the PegIntron 1 mcg/ribavirin arm, and 57% of subjects in the Pegasys 180 mcg/Copegus arm. In Study 2, PegIntron/ribavirin combination therapy induced fatigue or headache in approximately two-thirds of subjects, with fever or rigors in approximately half of the subjects. The severity of some of these systemic symptoms (e.g., fever and headache) tended to decrease as treatment continued. Subjects receiving ribavirin/PegIntron as re-treatment after failing a previous interferon combination regimen reported adverse reactions similar to those previously associated with this regimen during clinical trials of treatment-naïve subjects. Pediatric Subjects In general, the adverse reaction profile in the pediatric population was similar to that observed in adults. In the pediatric trial, the most prevalent adverse reactions were pyrexia (80%), headache (62%), neutropenia (33%), fatigue (30%), anorexia (29%), injection-site erythema (29%) and vomiting (27%). The majority of adverse reactions were mild or moderate in severity. Severe adverse reactions were reported in 7% (8/107) of all subjects and included injection site pain (1%), pain in extremity (1%), headache (1%), neutropenia (1%), and pyrexia (4%). Important adverse reactions that occurred in this subject population were nervousness (7%; 7/107), aggression (3%; 3/107), anger (2%; 2/107), and depression (1%; 1/107). Five subjects received levothyroxine treatment, three with clinical hypothyroidism and two with asymptomatic TSH elevations. Weight and height gain of pediatric subjects treated with PegIntron plus ribavirin lagged behind that predicted by normative population data for the entire length of treatment. Severely inhibited growth velocity (less than 3rd percentile) was observed in 70% of the subjects while on treatment. Dose modifications of PegIntron and/or ribavirin were required in 25% of subjects due to treatment-related adverse reactions, most commonly for anemia, neutropenia and weight loss. Two subjects (2%; 2/107) discontinued therapy as the result of an adverse reaction. Adverse reactions that occurred with a greater than or equal to 10% incidence in the pediatric trial subjects are provided in Table 7. Table 7: Percentage of Pediatric Subjects with Treatment-Related Adverse Reactions (in At Least 10% of All Subjects) System Organ Class Preferred Term All Subjects (N=107) Blood and Lymphatic System Disorders Neutropenia 33% Anemia 11% Leukopenia 10% Gastrointestinal Disorders Abdominal Pain 21% Abdominal Pain Upper 12% Vomiting 27% Nausea 18% General Disorders and Administration Site Conditions Pyrexia 80% Fatigue 30% Injection-site Erythema 29% Chills 21% Asthenia 15% Irritability 14% Investigations Weight Loss 19% Metabolism and Nutrition Disorders Anorexia 29% Decreased Appetite 22% Musculoskeletal and Connective Tissue Disorders Arthralgia 17% Myalgia 17% Nervous System Disorders Headache 62% Dizziness 14% Skin and Subcutaneous Tissue Disorders Alopecia 17% Ninety-four of 107 subjects enrolled in a 5-year follow-up trial. The long-term effects on growth were less in subjects treated for 24 weeks than in those treated for 48 weeks. Twenty-four percent of subjects (11/46) treated for 24 weeks and 40% of subjects (19/48) treated for 48 weeks had a >15 percentile height-for-age decrease from pre-treatment baseline to the end of 5-year follow-up. Eleven percent of subjects (5/46) treated for 24 weeks and 13% of subjects (6/48) treated for 48 weeks had a >30 percentile height-for-age decrease from pre-treatment baseline to the end of the 5-year follow-up. While observed across all age groups, the highest risk for reduced height at the end of long-term follow-up appeared to be initiation of combination therapy during the years of expected peak growth velocity [see Warnings and Precautions (5.9) ]. Laboratory Values Adult and Pediatric Subjects The adverse reaction profile in Study 3, which compared PegIntron/weight-based ribavirin combination to a PegIntron/flat dose ribavirin regimen, revealed an increased rate of anemia with weight-based dosing (29% vs. 19% for weight-based vs. flat dose regimens, respectively). However, the majority of cases of anemia were mild and responded to dose reductions. Changes in selected laboratory values during treatment in combination with ribavirin treatment are described below. Decreases in hemoglobin, leukocytes, neutrophils, and platelets may require dose reduction or permanent discontinuation from therapy [see Dosage and Administration (2.5) ] . Changes in selected laboratory values during therapy are described in Table 8. Most of the changes in laboratory values in the PegIntron/ribavirin trial with pediatrics were mild or moderate. Table 8: Selected Laboratory Abnormalities During Treatment with Ribavirin and PegIntron or Ribavirin and INTRON A in Previously Untreated Subjects * The table summarizes the worst category observed within the period per subject per laboratory test. Only subjects with at least one treatment value for a given laboratory test are included. † ULN=Upper limit of normal. Laboratory Parameters * Percentage of Subjects Adults (Study 2) Pediatrics PegIntron/ Ribavirin (N=511) INTRON A/ Ribavirin (N=505) PegIntron/ Ribavirin (N=107) * Hemoglobin (g/dL) 9.5 to <11.0 26 27 30 8.0 to <9.5 3 3 2 6.5 to 7.9 0.2 0.2 - Leukocytes (x 10 9 /L) 2.0 to 2.9 46 41 39 1.5 to <2.0 24 8 3 1.0 to 1.4 5 1 - Neutrophils (x 10 9 /L) 1.0 to 1.5 33 37 35 0.75 to <1.0 25 13 26 0.5 to <0.75 18 7 13 <0.5 4 2 3 Platelets (x 10 9 /L) 70 to 100 15 5 1 50 to <70 3 0.8 - 30 to 49 0.2 0.2 - 25 to <50 - - 1 Total Bilirubin (mg/dL) (µmole/L) 1.5 to 3.0 10 13 - 1.26 to 2.59 x ULN † - - 7 3.1 to 6.0 0.6 0.2 - 2.6 to 5 x ULN † - - - 6.1 to 12.0 0 0.2 - ALT (U/L) 2 x Baseline 0.6 0.2 1 2.1 to 5 x Baseline 3 1 5 5.1 to 10 x Baseline 0 0 3 Hemoglobin . In Study 2, hemoglobin levels decreased to less than 11 g/dL in about 30% of subjects. In Study 3, 47% of subjects receiving weight-based dosing of ribavirin and 33% on flat-dose ribavirin had decreases in hemoglobin levels to less than 11 g/dL. Reductions in hemoglobin to less than 9 g/dL occurred more frequently in subjects receiving weight-based dosing compared to flat dosing (4% and 2%, respectively). In Study 2, dose modification was required in 9% and 13% of subjects in the PegIntron/ribavirin and INTRON A/ribavirin groups. In Study 4, subjects receiving PegIntron (1.5 mcg/kg)/ribavirin had decreases in hemoglobin levels to between 8.5 to less than 10 g/dL (28%) and to less than 8.5 g/dL (3%), whereas in patients receiving Pegasys 180 mcg/Copegus these decreases occurred in 26% and 4% of subjects, respectively. On average, hemoglobin levels became stable by treatment Weeks 4 to 6. The typical pattern observed was a decrease in hemoglobin levels by treatment Week 4 followed by stabilization and a plateau, which was maintained to the end of treatment [see Dosage and Administration (2.5) ]. Neutrophils . In Study 2, decreases in neutrophil counts were observed in a majority of adult subjects treated with PegIntron/ribavirin (85%) and INTRON A/ribavirin (60%). Severe, potentially life-threatening neutropenia (less than 0.5 x 10 9 /L) occurred in approximately 4% of subjects treated with PegIntron/ribavirin and 2% of subjects treated with INTRON A/ribavirin. Eighteen percent of subjects receiving PegIntron/ribavirin required modification of interferon dosage. Few subjects (less than 1%) required permanent discontinuation of treatment. Neutrophil counts generally returned to pre-treatment levels 4 weeks after cessation of therapy [see Dosage and Administration (2.5) ] . Platelets . In Study 2, platelet counts decreased to less than 100,000/mm 3 in approximately 20% of subjects treated with PegIntron alone or with ribavirin and in 6% of adult subjects treated with INTRON A/ribavirin. Severe decreases in platelet counts (less than 50,000/mm 3 ) occur in less than 4% of adult subjects. In Study 2, 1% or 3% of subjects required dose modification of INTRON A or PegIntron, respectively. Platelet counts generally returned to pretreatment levels 4 weeks after the cessation of therapy [see Dosage and Administration (2.5) ] . Thyroid Function . In Study 2, clinically apparent thyroid disorders occurred among subjects treated with either INTRON A or PegIntron (with or without ribavirin) at a similar incidence (5% for hypothyroidism and 3% for hyperthyroidism). Subjects developed new onset TSH abnormalities while on treatment and during the follow-up period. At the end of the follow-up period, 7% of subjects still had abnormal TSH values. Bilirubin and Uric Acid . In Study 2, 10 to 14% of subjects developed hyperbilirubinemia and 33 to 38% developed hyperuricemia in association with hemolysis. Six subjects developed mild to moderate gout. Adverse Reactions with Ribavirin/INTRON A Combination Therapy Adult Subjects In clinical trials, 19% and 6% of previously untreated and relapse subjects, respectively, discontinued therapy due to adverse reactions in the combination arms compared to 13% and 3% in the interferon-only arms. Selected treatment-related adverse reactions that occurred in the U.S. trials with incidence 5% or greater are provided by treatment group (see Table 9). In general, the selected treatment-related adverse reactions were reported with lower incidence in the international trials as compared to the U.S. trials, except for asthenia, influenza-like symptoms, nervousness, and pruritus. Pediatric Subjects In clinical trials of 118 pediatric subjects 3 to 16 years of age, 6% discontinued therapy due to adverse reactions. Dose modifications were required in 30% of subjects, most commonly for anemia and neutropenia. In general, the adverse-reaction profile in the pediatric population was similar to that observed in adults. Injection site disorders, fever, anorexia, vomiting, and emotional lability occurred more frequently in pediatric subjects compared to adult subjects. Conversely, pediatric subjects experienced less fatigue, dyspepsia, arthralgia, insomnia, irritability, impaired concentration, dyspnea, and pruritus compared to adult subjects. Selected treatment-related adverse reactions that occurred with incidence 5% or greater among all pediatric subjects who received the recommended dose of ribavirin/INTRON A combination therapy are provided in Table 9. Table 9: Selected Treatment-Related Adverse Reactions: Previously Untreated and Relapse Adult Subjects and Previously Untreated Pediatric Subjects * Subjects reporting one or more adverse reactions. A subject may have reported more than one adverse reaction within a body system/organ class category. Subjects Reporting Adverse Reactions* Percentage of Subjects U.S. Previously Untreated Study U.S. Relapse Study Pediatric Subjects 24 weeks of treatment 48 weeks of treatment 24 weeks of treatment 48 weeks of treatment INTRON A/ Ribavirin (N=228) INTRON A/ Placebo (N=231) INTRON A/ Ribavirin (N=228) INTRON A/ Placebo (N=225) INTRON A/ Ribavirin (N=77) INTRON A/ Placebo (N=76) INTRON A/ Ribavirin (N=118) Application Site Disorders Injection Site Inflammation 13 10 12 14 6 8 14 Injection Site Reaction 7 9 8 9 5 3 19 Body as a Whole - General Disorders Headache 63 63 66 67 66 68 69 Fatigue 68 62 70 72 60 53 58 Rigors 40 32 42 39 43 37 25 Fever 37 35 41 40 32 36 61 Influenza-like Symptoms 14 18 18 20 13 13 31 Asthenia 9 4 9 9 10 4 5 Chest Pain 5 4 9 8 6 7 5 Central & Peripheral Nervous System Disorders Dizziness 17 15 23 19 26 21 20 Gastrointestinal System Disorders Nausea 38 35 46 33 47 33 33 Anorexia 27 16 25 19 21 14 51 Dyspepsia 14 6 16 9 16 9 <1 Vomiting 11 10 9 13 12 8 42 Musculoskeletal System Disorders Myalgia 61 57 64 63 61 58 32 Arthralgia 30 27 33 36 29 29 15 Musculoskeletal Pain 20 26 28 32 22 28 21 Psychiatric Disorders Insomnia 39 27 39 30 26 25 14 Irritability 23 19 32 27 25 20 10 Depression 32 25 36 37 23 14 13 Emotional Lability 7 6 11 8 12 8 16 Concentration Impaired 11 14 14 14 10 12 5 Nervousness 4 2 4 4 5 4 3 Respiratory System Disorders Dyspnea 19 9 18 10 17 12 5 Sinusitis 9 7 10 14 12 7 <1 Skin and Appendages Disorders Alopecia 28 27 32 28 27 26 23 Rash 20 9 28 8 21 5 17 Pruritus 21 9 19 8 13 4 12 Special Senses, Other Disorders Taste Perversion 7 4 8 4 6 5 <1 During a 48-week course of therapy there was a decrease in the rate of linear growth (mean percentile assignment decrease of 7%) and a decrease in the rate of weight gain (mean percentile assignment decrease of 9%). A general reversal of these trends was noted during the 24-week post-treatment period. Long-term data in a limited number of patients, however, suggests that combination therapy may induce a growth inhibition that results in reduced final adult height in some patients [see Warnings and Precautions (5.9) ]. Laboratory Values Changes in selected hematologic values (hemoglobin, white blood cells, neutrophils, and platelets) during therapy are described below (see Table 10). Hemoglobin . Hemoglobin decreases among subjects receiving ribavirin therapy began at Week 1, with stabilization by Week 4. In previously untreated subjects treated for 48 weeks, the mean maximum decrease from baseline was 3.1 g/dL in the U.S. trial and 2.9 g/dL in the international trial. In relapse subjects, the mean maximum decrease from baseline was 2.8 g/dL in the U.S. trial and 2.6 g/dL in the international trial. Hemoglobin values returned to pretreatment levels within 4 to 8 weeks of cessation of therapy in most subjects. Bilirubin and Uric Acid . Increases in both bilirubin and uric acid, associated with hemolysis, were noted in clinical trials. Most changes were moderate and reversed within 4 weeks after treatment discontinuation. This observation occurred most frequently in subjects with a previous diagnosis of Gilbert’s syndrome. This has not been associated with hepatic dysfunction or clinical morbidity. Table 10: Selected Laboratory Abnormalities During Treatment with Ribavirin and INTRON A: Previously Untreated and Relapse Adult Subjects and Previously Untreated Pediatric Subjects Percentage of Subjects U.S. Previously Untreated Study U.S. Relapse Study Pediatric Subjects 24 weeks of treatment 48 weeks of treatment 24 weeks of treatment 48 weeks of treatment INTRON A/ Ribavirin (N=228) INTRON A / Placebo (N=231) INTRON A/ Ribavirin (N=228) INTRON A/ Placebo (N=225) INTRON A/ Ribavirin (N=77) INTRON A / Placebo (N=76) INTRON A/ Ribavirin (N=118) Hemoglobin (g/dL) 9.5 to 10.9 24 1 32 1 21 3 24 8.0 to 9.4 5 0 4 0 4 0 3 6.5 to 7.9 0 0 0 0.4 0 0 0 <6.5 0 0 0 0 0 0 0 Leukocytes (x 10 9 /L) 2.0 to 2.9 40 20 38 23 45 26 35 1.5 to 1.9 4 1 9 2 5 3 8 1.0 to 1.4 0.9 0 2 0 0 0 0 <1.0 0 0 0 0 0 0 0 Neutrophils (x 10 9 /L) 1.0 to 1.49 30 32 31 44 42 34 37 0.75 to 0.99 14 15 14 11 16 18 15 0.5 to 0.74 9 9 14 7 8 4 16 <0.5 11 8 11 5 5 8 3 Platelets (x 10 9 /L) 70 to 99 9 11 11 14 6 12 0.8 50 to 69 2 3 2 3 0 5 2 30 to 49 0 0.4 0 0.4 0 0 0 <30 0.9 0 1 0.9 0 0 0 Total Bilirubin (mg/dL) 1.5 to 3.0 27 13 32 13 21 7 2 3.1 to 6.0 0.9 0.4 2 0 3 0 0 6.1 to 12.0 0 0 0.4 0 0 0 0 >12.0 0 0 0 0 0 0 0 6.2 Postmarketing Experiences The following adverse reactions have been identified and reported during post approval use of ribavirin in combination with INTRON A or PegIntron. 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, aplastic anemia Ear and Labyrinth disorders Hearing disorder, vertigo Respiratory, Thoracic and Mediastinal disorders Pulmonary hypertension Eye disorders Serous retinal detachment Endocrine disorders Diabetes

Nucleoside analogues: Closely monitor for toxicities. Discontinue nucleoside reverse transcriptase inhibitors or reduce dose or discontinue interferon, ribavirin or both with worsening toxicities. ( 7.2 ) 7.1 Didanosine Exposure to didanosine or its active metabolite (dideoxyadenosine 5’-triphosphate) is increased when didanosine is coadministered with ribavirin, which could cause or worsen clinical toxicities; therefore, coadministration of ribavirin capsules and didanosine is contraindicated [see Contraindications (4) ] . Reports of fatal hepatic failure, as well as peripheral neuropathy, pancreatitis, and symptomatic hyperlactatemia/lactic acidosis have been reported in clinical trials. 7.2 Nucleoside Analogues Hepatic decompensation (some fatal) has occurred in cirrhotic HIV/HCV co-infected patients receiving combination antiretroviral therapy for HIV and interferon alpha and ribavirin. Patients receiving interferon with ribavirin and nucleoside reverse transcriptase inhibitors (NRTIs) should be closely monitored for treatment-associated toxicities, especially hepatic decompensation and anemia. Discontinuation of NRTIs should be considered as medically appropriate (see labeling for individual NRTI product). Dose reduction or discontinuation of interferon, ribavirin, or both should also be considered if worsening clinical toxicities are observed, including hepatic decompensation (e.g., Child-Pugh greater than 6). Ribavirin may antagonize the cell culture antiviral activity of stavudine and zidovudine against HIV. Ribavirin has been shown in cell culture to inhibit phosphorylation of lamivudine, stavudine, and zidovudine, which could lead to decreased antiretroviral activity. However, in a study with another pegylated interferon in combination with ribavirin, no pharmacokinetic (e.g., plasma concentrations or intracellular triphosphorylated active metabolite concentrations) or pharmacodynamic (e.g., loss of HIV/HCV virologic suppress) interaction was observed when ribavirin and lamivudine (n=18), stavudine (n=10), or zidovudine (n=6) were coadministered as part of a multidrug regimen in HIV/HCV co-infected subjects. Concomitant use of ribavirin with any of these drugs should be done with caution. 7.3 Drugs Metabolized by Cytochrome P-450 Results of in vitro studies using both human and rat liver microsome preparations indicated little or no cytochrome P-450 enzyme-mediated metabolism of ribavirin, with minimal potential for P-450 enzyme-based drug interactions. No pharmacokinetic interactions were noted between INTRON A and ribavirin capsules in a multiple-dose pharmacokinetic study. 7.4 Azathioprine The use of ribavirin for the treatment of chronic hepatitis C in patients receiving azathioprine has been reported to induce severe pancytopenia and may increase the risk of azathioprine-related myelotoxicity. Inosine monophosphate dehydrogenase (IMDH) is required for one of the metabolic pathways of azathioprine. Ribavirin is known to inhibit IMDH, thereby leading to accumulation of an azathioprine metabolite, 6-methylthioinosine monophosphate (6-MTITP), which is associated with myelotoxicity (neutropenia, thrombocytopenia, and anemia). Patients receiving azathioprine with ribavirin should have complete blood counts, including platelet counts, monitored weekly for the first month, twice monthly for the second and third months of treatment, then monthly or more frequently if dosage or other therapy changes are necessary [see Warnings and Precautions (5.8) ].