Ribavirin tablets must not be used alone because ribavirin monotherapy is not effective for the treatment of chronic hepatitis C virus infection. The safety and efficacy of ribavirin tablets have only been established when used together with peginterferon alfa-2a (pegylated interferon alfa-2a, recombinant).
Ribavirin tablets and peginterferon alfa-2a should be discontinued in patients who develop evidence of hepatic decompensation during treatment.
There are significant adverse events caused by ribavirin tablets/peginterferon alfa-2a therapy, including severe depression and suicidal ideation, hemolytic anemia, suppression of bone marrow function, autoimmune and infectious disorders, pulmonary dysfunction, pancreatitis, and diabetes. The peginterferon alfa-2a package insert and MEDICATION GUIDE should be reviewed in their entirety prior to initiation of combination treatment for additional safety information.
Treatment with ribavirin tablets and peginterferon alfa-2a should be administered under the guidance of a qualified physician and may lead to moderate to severe adverse experiences requiring dose reduction, temporary dose cessation or discontinuation of therapy.
Ribavirin may cause birth defects and/or death of the exposed fetus. Extreme care must be taken to avoid pregnancy in female patients and in female partners of male patients. Ribavirin has demonstrated significant teratogenic and/or embryocidal effects in all animal species in which adequate studies have been conducted. These effects occurred at doses as low as one twentieth of the recommended human dose of ribavirin. RIBAVIRIN TABLETS THERAPY SHOULD NOT BE STARTED UNLESS A REPORT OF A NEGATIVE PREGNANCY TEST HAS BEEN OBTAINED IMMEDIATELY PRIOR TO PLANNED INITIATION OF THERAPY. Patients should be instructed to use at least two forms of effective contraception during treatment and for six-months after treatment has been stopped. Pregnancy testing should occur monthly during ribavirin tablets therapy and for 6 months after therapy has stopped (see CONTRAINDICATIONS and PRECAUTIONS: Information for Patients and Pregnancy: Category X).
The primary toxicity of ribavirin is hemolytic anemia (hemoglobin <10 g/dL), which was observed in approximately 13% of all ribavirin tablets and peginterferon alfa-2a treated patients in clinical trials (see PRECAUTIONS: Laboratory Tests). The anemia associated with ribavirin tablets occurs within 1 to 2 weeks of initiation of therapy. BECAUSE THE INITIAL DROP IN HEMOGLOBIN MAY BE SIGNIFICANT, IT IS ADVISED THAT HEMOGLOBIN OR HEMATOCRIT BE OBTAINED PRETREATMENT AND AT WEEK 2 AND WEEK 4 OF THERAPY OR MORE FREQUENTLY IF CLINICALLY INDICATED. Patients should then be followed as clinically appropriate.
Fatal and nonfatal myocardial infarctions have been reported in patients with anemia caused by ribavirin. Patients should be assessed for underlying cardiac disease before initiation of ribavirin therapy. Patients with pre-existing cardiac disease should have electrocardiograms administered before treatment, and should be appropriately monitored during therapy. If there is any deterioration of cardiovascular status, therapy should be suspended or discontinued (see DOSAGE AND ADMINISTRATION: Ribavirin Tablets Dosage Modification Guidelines). Because cardiac disease may be worsened by drug induced anemia, patients with a history of significant or unstable cardiac disease should not use ribavirin tablets (see ADVERSE REACTIONS).
Chronic hepatitis C (CHC) patients with cirrhosis may be at risk of hepatic decompensation and death when treated with alpha interferons, including peginterferon alfa-2a. Cirrhotic CHC patients coinfected with HIV receiving highly active antiretroviral therapy (HAART) and interferon alfa-2a with or without ribavirin appear to be at increased risk for the development of hepatic decompensation compared to patients not receiving HAART. In Study NR15961 (described as Study 6 in the peginterferon alfa-2a package insert), among 129 CHC/HIV cirrhotic patients receiving HAART, 14 (11%) of these patients across all treatment arms developed hepatic decompensation resulting in 6 deaths. All 14 patients were on NRTIs, including stavudine, didanosine, abacavir, zidovudine, and lamivudine. These small numbers of patients do not permit discrimination between specific NRTIs or the associated risk. During treatment, patients’ clinical status and hepatic function should be closely monitored, and peginterferon alfa-2a treatment should be immediately discontinued if decompensation (Child-Pugh score ≥6) is observed (see
Severe acute hypersensitivity reactions (e.g., urticaria, angioedema, bronchoconstriction, and anaphylaxis) have been rarely observed during alpha interferon and ribavirin therapy. If such reaction occurs, therapy with peginterferon alfa-2a and ribavirin should be discontinued and appropriate medical therapy immediately instituted. Serious skin reactions including vesiculobullous eruptions, reactions in the spectrum of Stevens Johnson Syndrome (erythema multiforme major) with varying degrees of skin and mucosal involvement and exfoliative dermatitis (erythroderma) have been rarely reported in patients receiving peginterferon alfa-2a with and without ribavirin. Patients developing signs or symptoms of severe skin reactions must discontinue therapy.(see ADVERSE REACTIONS: Postmarketing Experience).
Pulmonary symptoms, including dyspnea, pulmonary infiltrates, pneumonitis and occasional cases of fatal pneumonia, have been reported during therapy with ribavirin and interferon. In addition, sarcoidosis or the exacerbation of sarcoidosis has been reported. If there is evidence of pulmonary infiltrates or pulmonary function impairment, the patient should be closely monitored, and if appropriate, combination ribavirin tablets/peginterferon alfa-2a treatment should be discontinued.
Ribavirin tablets and peginterferon alfa-2a therapy should be suspended in patients with signs and symptoms of pancreatitis, and discontinued in patients with confirmed pancreatitis.
Ribavirin tablets should not be used in patients with creatinine clearance <50 mL/min (see
CLINICAL PHARMACOLOGY: Special Populations).
Ribavirin tablets must be discontinued immediately and appropriate medical therapy instituted if an acute hypersensitivity reaction (e.g., urticaria, angioedema, bronchoconstriction, anaphylaxis) develops. Transient rashes do not necessitate interruption of treatment.
The safety and efficacy of ribavirin tablets and peginterferon alfa-2a therapy for the treatment of adenovirus, RSV, parainfluenza or influenza infections have not been established. Ribavirin tablets should not be used for these indications. Ribavirin for inhalation has a separate package insert, which should be consulted if ribavirin inhalation therapy is being considered.
The safety and efficacy of ribavirin tablets and peginterferon alfa-2a therapy have not been established in liver or other organ transplant patients, patients with decompensated liver disease due to hepatitis C virus infection, patients who are non-responders to interferon therapy or patients coinfected with HBV or HIV and a CD4+ cell count <100 cells/μL.
Information for Patients
Patients must be informed that ribavirin may cause birth defects and/or death of the exposed fetus. Ribavirin tablets therapy must not be used by women who are pregnant or by men whose female partners are pregnant. Extreme care must be taken to avoid pregnancy in female patients and in female partners of male patients taking ribavirin tablets therapy and for 6 months posttherapy. Ribavirin tablets therapy should not be initiated until a report of a negative pregnancy test has been obtained immediately prior to initiation of therapy. Patients must perform a pregnancy test monthly during therapy and for 6 months posttherapy.
Female patients of childbearing potential and male patients with female partners of childbearing potential must be advised of the teratogenic/embryocidal risks and must be instructed to practice effective contraception during ribavirin tablets therapy and for 6 months posttherapy. Patients should be advised to notify the healthcare provider immediately in the event of a pregnancy (see
The most common adverse event associated with ribavirin is anemia, which may be severe (see
ADVERSE REACTIONS). Patients should be advised that laboratory evaluations are required prior to starting ribavirin tablets therapy and periodically thereafter (see
Laboratory Tests). It is advised that patients be well hydrated, especially during the initial stages of treatment.
Patients who develop dizziness, confusion, somnolence, and fatigue should be cautioned to avoid driving or operating machinery.
Patients should be informed regarding the potential benefits and risks attendant to the use of ribavirin tablets. Instructions on appropriate use should be given, including review of the contents of the enclosed MEDICATION GUIDE, which is not a disclosure of all or possible adverse effects.
Patients should be advised to take ribavirin tablets with food.
Before beginning ribavirin tablets therapy, standard hematological and biochemical laboratory tests must be conducted for all patients. Pregnancy screening for women of childbearing potential must be done.
After initiation of therapy, hematological tests should be performed at 2 weeks and 4 weeks and biochemical tests should be performed at 4 weeks. Additional testing should be performed periodically during therapy. Monthly pregnancy testing should be done during combination therapy and for 6 months after discontinuing therapy.
The entrance criteria used for the clinical studies of ribavirin tablets and peginterferon alfa-2a combination therapy may be considered as a guideline to acceptable baseline values for initiation of treatment:
Platelet count ≥ 90,000 cells/mm3 (as low as 75,000 cells/mm3 in patients with cirrhosis or 70,000 cells/mm3 in patients with CHC and HIV)
Absolute neutrophil count (ANC) ≥ 1500 cells/mm3
TSH and T4 within normal limits or adequately controlled thyroid function
CD4+ cell count ≥ 200 cells/µL or CD4+ cell count ≥100 cells/µL but <200 cells/µL and HIV-1 RNA <5000 copies/mL in patients coinfected with HIV
Hemoglobin ≥12 g/dL for women and ≥13 g/dL for men in CHC monoinfected patients
Hemoglobin ≥11 g/dL for women and ≥12 g/dL for men in patients with CHC and HIV
The maximum drop in hemoglobin usually occurred during the first 8 weeks of initiation of ribavirin tablets therapy. Because of this initial acute drop in hemoglobin, it is advised that a complete blood count should be obtained pretreatment and at week 2 and week 4 of therapy or more frequently if clinically indicated. Additional testing should be performed periodically during therapy. Patients should then be followed as clinically appropriate.
Results from a pharmacokinetic sub-study demonstrated no pharmacokinetic interaction between peginterferon alfa-2a and ribavirin.
In Study NR15961 among the CHC/HIV coinfected cirrhotic patients receiving NRTIs cases of hepatic decompensation (some fatal) were observed (see
WARNINGS: Hepatic Failure).
Patients receiving peginterferon alfa-2a/ribavirin tablets and NRTIs should be closely monitored for treatment associated toxicities. Physicians should refer to prescribing information for the respective NRTIs for guidance regarding toxicity management. In addition, dose reduction or discontinuation of peginterferon alfa-2a, ribavirin tablets or both should also be considered if worsening toxicities are observed (see
DOSAGE AND ADMINISTRATION: Dose Modifications).
Co-administration of ribavirin tablets and didanosine is not recommended. Reports of fatal hepatic failure, as well as peripheral neuropathy, pancreatitis, and symptomatic hyperlactatemia/lactic acidosis have been reported in clinical trials (see
CLINICAL PHARMACOLOGY: Drug Interactions).
In Study NR15961, patients who were administered zidovudine in combination with peginterferon alfa-2a/ribavirin tablets developed severe neutropenia (ANC <500) and severe anemia (hemoglobin <8 g/dL) more frequently than similar patients not receiving zidovudine (neutropenia 15% vs. 9%) (anemia 5% vs. 1%).
Lamivudine, Stavudine, and Zidovudine
In vitro studies have shown ribavirin can reduce the phosphorylation of pyrimidine nucleoside analogs such as lamivudine, stavudine, and zidovudine. No evidence of a pharmacokinetic or pharmacodynamic interaction was seen when ribavirin was co-administered with lamivudine, stavudine, and/or zidovudine in HIV/HCV coinfected patients (see
CLINICAL PHARMACOLOGY: Drug Interactions).
Carcinogenesis, Mutagenesis, Impairment of Fertility
In a p53 (+/-) mouse carcinogenicity study and a rat 2-year carcinogenicity study at doses up to the maximum tolerated doses of 100 mg/kg/day and 60 mg/kg/day, respectively, ribavirin was not oncogenic. On a body surface area basis, these doses are approximately 0.5 and 0.6 times the maximum recommended human 24-hour dose of ribavirin.
Ribavirin demonstrated mutagenic activity in the in vitro mouse lymphoma assay. No clastogenic activity was observed in an in vivo mouse micronucleus assay at doses up to 2000 mg/kg. However, results from studies published in the literature show clastogenic activity in the in vivo mouse micronucleus assay at oral doses up to 2000 mg/kg. A dominant lethal assay in rats was negative, indicating that if mutations occurred in rats they were not transmitted through male gametes. However, potential carcinogenic risk to humans cannot be excluded.
Impairment of Fertility
In a fertility study in rats, ribavirin showed a marginal reduction in sperm counts at the dose of 100 mg/kg/day with no effect on fertility. Upon cessation of treatment, total recovery occurred after 1 spermatogenesis cycle. Abnormalities in sperm were observed in studies in mice designed to evaluate the time course and reversibility of ribavirin-induced testicular degeneration at doses of 15 to 150 mg/kg/day (approximately 0.1 to 0.8 times the maximum recommended human 24-hour dose of ribavirin) administered for 3 to 6 months. Upon cessation of treatment, essentially total recovery from ribavirin-induced testicular toxicity was apparent within 1 or 2 spermatogenic cycles.
Female patients of childbearing potential and male patients with female partners of childbearing potential should not receive ribavirin tablets unless the patient and his/her partner are using effective contraception (two reliable forms). Based on a multiple dose half-life (t1/2) of ribavirin of 12 days, effective contraception must be utilized for 6 months posttherapy (i.e., 15 half-lives of clearance for ribavirin).
No reproductive toxicology studies have been performed using peginterferon alfa-2a in combination with ribavirin tablets. However, peginterferon alfa-2a and ribavirin when administered separately, each has adverse effects on reproduction. It should be assumed that the effects produced by either agent alone would also be caused by the combination of the two agents.
Pregnancy: Category X (see
Ribavirin produced significant embryocidal and/or teratogenic effects in all animal species in which adequate studies have been conducted. Malformations of the skull, palate, eye, jaw, limbs, skeleton, and gastrointestinal tract were noted. The incidence and severity of teratogenic effects increased with escalation of the drug dose. Survival of fetuses and offspring was reduced.
In conventional embryotoxicity/teratogenicity studies in rats and rabbits, observed no-effect dose levels were well below those for proposed clinical use (0.3 mg/kg/day for both the rat and rabbit; approximately 0.06 times the recommended human 24-hour dose of ribavirin). No maternal toxicity or effects on offspring were observed in a peri/postnatal toxicity study in rats dosed orally at up to 1 mg/kg/day (approximately 0.01 times the maximum recommended human 24-hour dose of ribavirin).
Treatment and Posttreatment: Potential Risk to the Fetus
Ribavirin is known to accumulate in intracellular components from where it is cleared very slowly. It is not known whether ribavirin is contained in sperm, and if so, will exert a potential teratogenic effect upon fertilization of the ova. In a study in rats, it was concluded that dominant lethality was not induced by ribavirin at doses up to 200 mg/kg for 5 days (up to 1.7 times the maximum recommended human dose of ribavirin). However, because of the potential human teratogenic effects of ribavirin, male patients should be advised to take every precaution to avoid risk of pregnancy for their female partners.
Ribavirin tablets should not be used by pregnant women or by men whose female partners are pregnant. Female patients of childbearing potential and male patients with female partners of childbearing potential should not receive ribavirin tablets unless the patient and his/her partner are using effective contraception (two reliable forms) during therapy and for 6 months posttherapy.
Ribavirin Pregnancy Registry
A Ribavirin Pregnancy Registry has been established to monitor maternal-fetal outcomes of pregnancies of female patients and female partners of male patients exposed to ribavirin during treatment and for six months following cessation of treatment. Healthcare providers and patients are encouraged to report such cases by calling 1-800-593-2214.
Long-term study in the mouse and rat (18 to 24 months; dose 20 to 75 and 10 to 40 mg/kg/day, respectively, approximately 0.1 to 0.4 times the maximum human daily dose of ribavirin) have demonstrated a relationship between chronic ribavirin exposure and an increased incidence of vascular lesions (microscopic hemorrhages) in mice. In rats, retinal degeneration occurred in controls, but the incidence was increased in ribavirin-treated rats.
It is not known whether ribavirin is excreted in human milk. Because many drugs are excreted in human milk and to avoid any potential for serious adverse reactions in nursing infants from ribavirin, a decision should be made either to discontinue nursing or therapy with ribavirin tablets, based on the importance of the therapy to the mother.
Safety and effectiveness of ribavirin tablets have not been established in patients below the age of 18.
Clinical studies of ribavirin tablets and peginterferon alfa-2a did not include sufficient numbers of subjects aged 65 or over to determine whether they respond differently from younger subjects. Specific pharmacokinetic evaluations for ribavirin in the elderly have not been performed. The risk of toxic reactions to this drug may be greater in patients with impaired renal function. Ribavirin tablets should not be administered to patients with creatinine clearance <50 mL/min. (see
CLINICAL PHARMACOLOGY: Special Populations).
Effect of Gender
No clinically significant differences in the pharmacokinetics of ribavirin were observed between male and female subjects.