Rebetol 200 mg hard capsules

Each hard capsule contains 200 mg of ribavirin.

Excipient: each hard capsule contains 40 mg of lactose monohydrate.

For a full list of excipients, see section 6.1.

Hard capsule

White, opaque and imprinted with blue ink.

Tritherapy:

Rebetol in combination with boceprevir and peginterferon alfa-2b is indicated for the treatment of chronic hepatitis C (CHC) genotype 1 infection in adults patients (18 years of age and older) with compensated liver disease who are previously untreated or who have failed previous therapy.

Please refer to peginterferon alfa -2b and boceprevir SmPCs when using Rebetol in combination with these medicines.

Bitherapy:

Rebetol is indicated for the treatment of chronic hepatitis C virus infection in adults, children 3 years of age and older and adolescents and must only be used as part of a combination regimen with peginterferon alfa-2b or interferon alfa-2b. Rebetol monotherapy must not be used.

Please refer to interferon alfa-2b and peginterferon alfa-2b SmPCs when using Rebetol in combination with these medicines.

There is no safety or efficacy information on the use of Rebetol with other forms of interferon (i.e., not alfa-2b).

Previously untreated (naïve) patients

Adult patients (18 years of age or older): Rebetol is indicated for:

• tritherapy - in combination with peginterferon alfa-2b and boceprevir for the treatment of adult patients with chronic hepatitis C genotype 1 infection with compensated liver disease.

• bitherapy - in combination with interferon alfa-2b or peginterferon alfa-2b, for the treatment of adult patients with chronic hepatitis C, not previously treated, without liver decompensation, with elevated alanine aminotransferase (ALT), who are positive for hepatitis C viral ribonucleic acid (HCV-RNA).

• bitherapy – for the treatment of CHC infection in combination with peginterferon alfa-2b for patients with compensated cirrhosis and/or clinically stable HIV co-infection (see section 4.4).

Bitherapy

Paediatric patients (children 3 years of age and older and adolescents): Rebetol is indicated, in a combination regimen with peginterferon alfa-2b or interferon alfa-2b, for the treatment of children 3 years of age and older and adolescents, who have chronic hepatitis C, not previously treated, without liver decompensation, and who are positive for HCV-RNA.

When deciding to not to defer treatment until adulthood, it is important to consider that the combination therapy induced a growth inhibition. The reversibility of growth inhibition is uncertain. The decision to treat should be made on a case by case basis (see section 4.4).

Previously treated patients

Adult patients: Rebetol is indicated for:

• tritherapy - in combination with peginterferon alfa-2b and boceprevir for the treatment of adult patients having CHC genotype 1 infection with compensated liver disease.

• bitherapy - in combination with peginterferon alfa-2b, for the treatment of patients with chronic hepatitis C who have failed previous treatment with interferon alpha (pegylated or non-pegylated) alone or in combination with ribavirin (see section 5.1).

• bitherapy - in combination with interferon alfa-2b, for the treatment of patients with chronic hepatitis C who have previously responded (with normalisation of ALT at the end of treatment) to interferon alfa monotherapy but who have subsequently relapsed.

Treatment should be initiated, and monitored, by a physician experienced in the management of chronic hepatitis C.

Rebetol must be used in combination with either peginterferon alfa-2b or interferon alfa-2b (bitherapy), or, in adult patients with chronic hepatitis C genotype 1 infection, in combination with boceprevir and peginterferon alfa-2b (tritherapy).

Please refer also to the boceprevir, peginterferon alfa-2b or interferon alfa-2b Summary of Product Characteristics (SmPC) for prescribing information particular to that product.

Dose to be administered

The dose of Rebetol is based on patient body weight. Rebetol capsules are to be administered orally each day in two divided doses (morning and evening) with food.

Adult patients:

The dose of Rebetol is based on patient body weight (Table 1).

Rebetol must be used in combination with either peginterferon alfa-2b (1.5 micrograms/kg/week) or interferon alfa-2b (3 million international units [MIU] three times a week). The choice of combination regimen is based on the characteristics of the patient. The regimen administered should be selected based on the anticipated efficacy and safety of the combination treatment for an individual patient (see section 5.1). Refer to the SmPC for boceprevir for the details of how boceprevir is to be administered in tritherapy.

a: 2 morning, 2 evening

b: 2 morning, 3 evening

c: 3 morning, 3 evening

d: 3 morning, 4 evening

Rebetol capsules in combination with boceprevir and peginterferon alfa-2b, or with peginterferon alfa-2b:

Duration of treatment – Naïve patients

Tritherapy:

Refer to the SmPCs for boceprevir and peginterferon alfa-2b.

Bitherapy with peginterferon alfa-2b:

Predictability of sustained virological response: Patients infected with virus genotype 1 who fail to achieve undetectable HCV-RNA or demonstrate adequate virological response at week 4 or 12 are highly unlikely to become sustained virological responders and should be eva luated for discontinuation (see also section 5.1).

• Genotype 1:

- Patients who have undetectable HCV-RNA at treatment week 12, treatment should be continued for another nine month period (i.e., a total of 48 weeks).

- Patients with detectable but ≥ 2 log decrease in HCV-RNA level from baseline at treatment week 12 should be reassessed at treatment week 24 and, if HCV-RNA is undetectable, they should continue with full course of therapy (i.e., a total of 48 weeks). However, if HCV-RNA is still detectable at treatment week 24, discontinuation of therapy should be considered.

- In the subset of patients with genotype 1 infection and low viral load (< 600,000 IU/ml) who become HCV-RNA negative at treatment week 4 and remain HCV-RNA negative at week 24, the treatment could either be stopped after this 24 week treatment course or pursued for an additional 24 weeks (i.e. overall 48 weeks treatment duration). However, an overall 24 weeks treatment duration may be associated with a higher risk of relapse than a 48 weeks treatment duration (see section 5.1).

• Genotype 2 or 3: It is recommended that all patients be treated with bitherapy for 24 weeks, except for HCV/HIV co-infected patients who should receive 48 weeks of treatment.

• Genotype 4: In general, patients infected with genotype 4 are considered harder to treat and limited study data (n=66) indicate they are compatible with a duration of treatment with bitherapy as for genotype 1.

Duration of treatment - naïve HCV/HIV co-infected patients

Bitherapy:

The recommended duration of Rebetol weight-based dosing (see Table 1) for HCV/HIV co-infected patients is 48 weeks with bitherapy, regardless of genotype.

Predictability of response and non-response in naïve HCV/HIV Co-infection

Early virological response by week 12, defined as a 2 log viral load decrease or undetectable levels of HCV-RNA, has been shown to be predictive for sustained response. The negative predictive value for sustained response in HCV/HIV co-infected patients treated with Rebetol in combination with peginterferon alfa-2b was 99 % (67/68; Study 1) (see section 5.1). A positive predictive value of 50 % (52/104; Study 1) was observed for HCV/HIV co-infected patients receiving bitherapy.

Duration of treatment - Retreatment patients

Tritherapy:

Refer to the SmPC for boceprevir and peginterferon alfa-2b.

Bitherapy with peginterferon alfa-2b:

Predictability of sustained virological response: All patients, irrespective of genotype, who have demonstrated serum HCV-RNA below the limits of detection at week 12 should receive 48 weeks of bitherapy. Retreated patients who fail to achieve virological response (i.e. HCV-RNA below the limits of detection) at week 12 are unlikely to become sustained virological responders after 48 weeks of therapy (see also section 5.1).

Retreatment duration greater than 48 weeks in non-responder patients with genotype 1 has not been studied with pegylated interferon alfa-2b and ribavirin combination therapy.

Rebetol capsules in combination with interferon alfa-2b (bitherapy only):

Duration of treatment with interferon alfa-2b:

Based on the results of clinical trials, it is recommended that patients be treated with bitherapy for at least six months. During those clinical trials in which patients were treated for one year, patients who failed to show a virological response after six months of treatment (HCV-RNA below lower limit of detection) were unlikely to become sustained virological responders (HCV-RNA below lower limit of detection six months after withdrawal of treatment).

• Genotype 1: Treatment with bitherapy should be continued for another six month period (i.e., a total of one year) in patients who exhibit negative HCV-RNA after six months of treatment.

• Genotypes Non-1: The decision to extend therapy with bitherapy to one year in patients with negative HCV-RNA after six months of treatment should be based on other prognostic factors (e.g., age > 40 years, male gender, bridging fibrosis).

Paediatric patients (bitherapy):

Note: For patients who weigh < 47 kg, or are unable to swallow capsules, please refer to the SmPC for ribavirin 40 mg/ml oral solution.

Dosing for children and adolescent patients is determined by body weight for Rebetol and by body surface area for peginterferon alfa-2b and interferon alfa-2b.

Dose to be administered for the combination therapy with peginterferon alfa-2b in paediatric patients:

The recommended dose of peginterferon alfa-2b is 60 µg/m²/week subcutaneously in combination with Rebetol 15 mg/kg/day (Table 2).

Dose to be administered for the combination therapy with interferon alfa-2b in paediatric patients:

In clinical studies performed in this population ribavirin and interferon alfa-2b were used in doses of 15 mg/kg/day and 3 million international units (MIU)/m² three times a week respectively (Table 2).

^a1 morning, 2 evening

^b2 morning, 2 evening

Duration of treatment in paediatric patients

• Genotype 1: The recommended duration of treatment with bitherapy is 1 year. By extrapolation from clinical data on combination therapy with standard interferon in paediatric patients (negative predictive value 96 % for interferon alfa-2b/Rebetol), patients who fail to achieve virological response at 12 weeks are highly unlikely to become sustained virological responders. Therefore, it is recommended that children and adolescent patients receiving interferon alfa-2b (pegylated or non-pegylated)/Rebetol combination be discontinued from therapy if their week 12 HCV-RNA dropped < 2 log₁₀ compared to pretreatment, or if they have detectable HCV-RNA at treatment week 24.

• Genotype 2 or 3: The recommended duration of treatment with bitherapy is 24 weeks.

• Genotype 4: Only 5 children and adolescents with Genotype 4 were treated in the peginterferon alfa-2b/Rebetol clinical trial. The recommended duration of treatment with bitherapy is 1 year. It is recommended that children and adolescent patients receiving peginterferon alfa-2b/Rebetol combination be discontinued from therapy if their week 12 HCV-RNA dropped < 2 log₁₀ compared to pretreatment, or if they have detectable HCV-RNA at treatment week 24.

Dose modification for all patients

Combination therapy:

If severe adverse reactions or laboratory abnormalities develop during combination therapy with Rebetol and peginterferon alfa-2b or interferon alfa-2b, or with Rebetol and peginterferon alfa-2b and boceprevir, modify the dosages as indicated in Table 3 if appropriate, until the adverse reactions abate. Dose reduction of boceprevir is not recommended. Guidelines were developed in clinical trials for dose modification (see Dosage modification guidelines, Table 3). As adherence might be of importance for outcome of therapy, the dose should be kept as close as possible to the recommended standard dose. The potential negative impact of ribavirin dose reduction on efficacy results could not be ruled out.

^* Upper limit of normal

** Refer to the SmPC for pegylated interferon alfa-2b and interferon alfa-2b for dose modification and discontinuation.

Note 1: In adult patients, 1^st dose reduction of Rebetol 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 Rebetol is by an additional 200 mg/day. Patients whose dose of Rebetol is reduced to 600 mg daily receive one 200 mg capsule in the morning and two 200 mg capsules in the evening.

In children and adolescent patients treated with Rebetol plus peginterferon alfa-2b, 1^st dose reduction of Rebetol is to 12 mg/kg/day, 2^nd dose reduction of Rebetol is to 8 mg/kg/day.

In children and adolescent patients treated with Rebetol plus interferon alfa-2b, reduce Rebetol dose to 7.5 mg/kg/day.

Note 2: In adult patients treated with Rebetol plus peginterferon alfa-2b, 1^st dose reduction of peginterferon alfa-2b is to 1 µg/kg/week. If needed, 2^nd dose reduction of peginterferon alfa-2b is to 0.5 µg/kg/week.

In children and adolescent patients treated with Rebetol plus peginterferon alfa-2b, 1^st dose reduction of peginterferon alfa-2b is to 40 µg/m²/week, 2^nd dose reduction of peginterferon alfa-2b is to 20 µg/m²/week.

In adult patients and children and adolescent patients treated with Rebetol plus interferon alfa-2b, reduce the interferon alfa-2b dose by one-half dose.

Special populations

Use in renal impairment: The pharmacokinetics of ribavirin are altered in patients with renal dysfunction due to reduction of apparent creatinine clearance in these patients (see section 5.2). Therefore, it is recommended that renal function be eva luated in all patients prior to initiation of Rebetol. Patients with creatinine clearance < 50 ml/minute must not be treated with Rebetol (see section 4.3). Patients with impaired renal function should be more carefully monitored with respect to the development of anaemia. If serum creatinine rises to > 2.0 mg/dl (Table 3), Rebetol and peginterferon alfa-2b/interferon alfa-2b must be discontinued.

Use in hepatic impairment: No pharmacokinetic interaction appears between ribavirin and hepatic function (see section 5.2). Therefore, no dose adjustment of Rebetol is required in patients with hepatic impairment. The use of ribavirin is contraindicated in patients with severe hepatic impairment or decompensated cirrhosis (see section 4.3).

Use in the elderly ( ≥ 65 years of age): There does not appear to be a significant age-related effect on the pharmacokinetics of ribavirin. However, as in younger patients, renal function must be determined prior to administration of Rebetol (see section 5.2).

Use in patients under the age of 18 years: Rebetol may be used in combination with peginterferon alfa-2b or interferon alfa-2b in children 3 years of age and older and adolescents. The selection of formulation is based on individual characteristics of the patient. Safety and effectiveness of Rebetol with other forms of interferon (i.e. not alfa-2b) in these patients have not been eva luated.

Patients co-infected with HCV/HIV: Patients taking nucleoside reverse transcriptase inhibitor (NRTI) treatment in association with ribavirin and interferon alfa-2b or peginterferon alfa-2b may be at increased risk of mitochondrial toxicity, lactic acidosis and hepatic decompensation (see section 4.4). Please refer also to the relevant product information for antiretroviral medicinal products.

Method of administration:

Rebetol should be administered orally. No special precautions for disposal or handling are required.

- Hypersensitivity to the active substance or to any of the excipients.

- Pregnant women (see sections 4.4, 4.6 and 5.3). Rebetol must not be initiated until a report of a negative pregnancy test has been obtained immediately prior to initiation of therapy.

- Lactation.

- A history of severe pre-existing cardiac disease, including unstable or uncontrolled cardiac disease, in the previous six months (see section 4.4).

- Patients with severe, debilitating medical conditions.

- Patients with chronic renal failure, patients with creatinine clearance < 50 ml/minute and/or on haemodialysis.

- Severe hepatic impairment (Child-Pugh Classification B or C) or decompensated cirrhosis of the liver.

- Haemoglobinopathies (e.g., thalassemia, sickle-cell anaemia).

- Initiation of peginterferon alfa-2b is contraindicated in HCV/HIV patients with cirrhosis and a Child-Pugh score ≥ 6.

Children and adolescents:

- Existence of, or history of severe psychiatric condition, particularly severe depression, suicidal ideation, or suicide attempt.

Because of co-administration with peginterferon alfa-2b or interferon alfa-2b:

- Autoimmune hepatitis; or history of autoimmune disease.

Based on results of clinical trials, the use of ribavirin as monotherapy is not effective and Rebetol must not be used alone. The safety and efficacy of combination therapy have been established only using ribavirin together with peginterferon alfa-2b or interferon alfa-2b solution for injection.

All patients in selected chronic hepatitis C studies had a liver biopsy before inclusion, but in certain cases (i.e. patients with genotype 2 and 3), treatment may be possible without histological confirmation. Current treatment guidelines should be consulted as to whether a liver biopsy is needed prior to commencing treatment.

Haemolysis: A decrease in haemoglobin levels to < 10 g/dl was observed in up to 14 % of adult patients and 7 % of children and adolescents treated with Rebetol in combination with peginterferon alfa-2b or interferon alfa-2b in clinical trials. Although ribavirin has no direct cardiovascular effects, anaemia associated with Rebetol may result in deterioration of cardiac function, or exacerbation of the symptoms of coronary disease, or both. Thus, Rebetol must be administered with caution to patients with pre-existing cardiac disease (see section 4.3). Cardiac status must be assessed before start of therapy and monitored clinically during therapy; if any deterioration occurs, therapy must be stopped (see section 4.2).

Cardiovascular: Adult patients with a history of congestive heart failure, myocardial infarction and/or previous or current arrhythmic disorders must be closely monitored. It is recommended that those patients who have pre-existing cardiac abnormalities have electrocardiograms taken prior to and during the course of treatment. Cardiac arrhythmias (primarily supraventricular) usually respond to conventional therapy but may require discontinuation of therapy. There are no data in children or adolescents with a history of cardiac disease.

Acute hypersensitivity: If an acute hypersensitivity reaction (e.g., urticaria, angioedema, bronchoconstriction, anaphylaxis) develops, Rebetol must be discontinued immediately and appropriate medical therapy instituted. Transient rashes do not necessitate interruption of treatment.

Ocular changes: Ribavirin is used in combination therapy with alpha interferons. Retinopathy including retinal haemorrhages, retinal exudates, papilloedema, optic neuropathy and retinal artery or vein occlusion which may result in loss of vision have been reported in rare instances with combination therapy with alpha interferons. All patients should have a baseline eye examination. Any patient complaining of decrease or loss of vision must have a prompt and complete eye examination. Patients with preexisting ophthalmologic disorders (e.g., diabetic or hypertensive retinopathy) should receive periodic ophthalmologic exams during combination therapy with alpha interferons. Combination therapy with alpha interferons should be discontinued in patients who develop new or worsening ophthalmologic disorders.

Liver function: Any patient developing significant liver function abnormalities during treatment must be monitored closely. Discontinue treatment in patients who develop prolongation of coagulation markers which might indicate liver decompensation.

Potential to exacerbate immunosuppression: Pancytopenia and bone marrow suppression have been reported in the literature to occur within 3 to 7 weeks after the administration of a peginterferon and ribavirin concomitantly with azathioprine. This myelotoxicity was reversible within 4 to 6 weeks upon withdrawal of HCV antiviral therapy and concomitant azathioprine and did not recur upon reintroduction of either treatment alone (see section 4.5).

Thyroid supplemental monitoring specific for children and adolescents:

Approximately 12 to 21 % of children treated with Rebetol and interferon alfa-2b (pegylated and non-pegylated) developed increase in thyroid stimulating hormone (TSH). Another approximately 4 % had a transient decrease below the lower limit of normal. Prior to initiation of interferon alfa-2b therapy, TSH levels must be eva luated and any thyroid abnormality detected at that time must be treated with conventional therapy. Interferon alfa-2b (pegylated and non-pegylated) therapy may be initiated if TSH levels can be maintained in the normal range by medication. Thyroid dysfunction during treatment with Rebetol and interferon alfa-2b and during treatment with Rebetol and peginterferon alfa-2b has been observed. If thyroid abnormalities are detected, the patient's thyroid status should be eva luated and treated as clinically appropriate. Children and adolescents should be monitored every 3 months for evidence of thyroid dysfunction (e.g. TSH).

HCV/HIV Co-infection:

Mitochondrial toxicity and lactic acidosis:

Caution should be taken in HIV-positive subjects co-infected with HCV who receive nucleoside reverse transcriptase inhibitor (NRTI) treatment (especially ddI and d4T) and associated interferon alfa-2b/ribavirin treatment. In the HIV-positive population receiving an NRTI regimen, physicians should carefully monitor markers of mitochondrial toxicity and lactic acidosis when ribavirin is administered. In particular:

- co-administration of Rebetol and didanosine is not recommended due to the risk of mitochondrial toxicity (see section 4.5).

- co-administration of Rebetol and stavudine should be avoided to limit the risk of overlapping mitochondrial toxicity.

Hepatic decompensation in HCV/HIV co-infected patients with advanced cirrhosis:

Co-infected patients with advanced cirrhosis receiving highly active anti-retroviral therapy (HAART) may be at increased risk of hepatic decompensation and death. Adding treatment with alfa interferons alone or in combination with ribavirin may increase the risk in this patient subset. Other baseline factors in co-infected patients that may be associated with a higher risk of hepatic decompensation include treatment with didanosine and elevated bilirubin serum concentrations.

Co-infected patients receiving both antiretroviral (ARV) and anti-hepatitis treatment should be closely monitored, assessing their Child-Pugh score during treatment. Patients progressing to hepatic decompensation should have their anti-hepatitis treatment immediately discontinued and the ARV treatment reassessed.

Haematological abnormalities in HCV/HIV co-infected patients:

HCV/HIV co-infected patients receiving peginterferon alfa-2b/ribavirin treatment and HAART may be at increased risk to develop haematological abnormalities (as neutropenia, thrombocytopenia and anaemia) compared to HCV mono-infected patients. Although, the majority of them could be managed by dose reduction, close monitoring of haematological parameters should be undertaken in this population of patients (see section 4.2 and below “Laboratory tests” and section 4.8).

Patients treated with ribavirin and zidovudine are at increased risk of developing anaemia; therefore, the concomitant use of ribavirin with zidovudine is not recommended (see section 4.5).

Patients with low CD4 counts:

In patients co-infected with HCV/HIV, limited efficacy and safety data (N = 25) are available in subjects with CD4 counts less than 200 cells/µl. Caution is therefore warranted in the treatment of patients with low CD4 counts.

Please refer to the respective Summary of Product Characteristics of the antiretroviral medicinal products that are to be taken concurrently with HCV therapy for awareness and management of toxicities specific for each product and the potential for overlapping toxicities with Rebetol and peginterferon alfa-2b.

Dental and periodontal disorders: Dental and periodontal disorders, which may lead to loss of teeth, have been reported in patients receiving Rebetol and peginterferon alfa-2b or interferon alfa-2b combination therapy. In addition, dry mouth could have a damaging effect on teeth and mucous membranes of the mouth during long-term treatment with the combination of Rebetol and peginterferon alfa-2b or interferon alfa-2b. Patients should brush their teeth thoroughly twice daily and have regular dental examinations. In addition some patients may experience vomiting. If this reaction occurs, they should be advised to rinse out their mouth thoroughly afterwards.

Laboratory tests: Standard haematologic tests and blood chemistries (complete blood count [CBC] and differential, platelet count, electrolytes, serum creatinine, liver function tests, uric acid) must be conducted in all patients prior to initiating therapy. Acceptable baseline values that may be considered as a guideline prior to initiation of Rebetol therapy:

Laboratory eva luations are to be conducted at weeks 2 and 4 of therapy, and periodically thereafter as clinically appropriate. HCV-RNA should be measured periodically during treatment (see section 4.2).

For females of childbearing potential: Female patients must have a routine pregnancy test performed monthly during treatment and for four months thereafter. Female partners of male patients must have a routine pregnancy test performed monthly during treatment and for seven months thereafter (see section 4.6).

Uric acid may increase with Rebetol due to haemolysis; therefore, the potential for development of gout must be carefully monitored in pre-disposed patients.

Use in patients with rare hereditary disorders: Each Rebetol capsule contains 40 mg of lactose.

Patients with rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.

Results of in vitro studies using both human and rat liver microsome preparations indicated no cytochrome P450 enzyme mediated metabolism of ribavirin. Ribavirin does not inhibit cytochrome P450 enzymes. There is no evidence from toxicity studies that ribavirin induces liver enzymes. Therefore, there is a minimal potential for P450 enzyme-based interactions.

Ribavirin, by having an inhibitory effect on inosine monophosphate dehydrogenase, may interfere with azathioprine metabolism possibly leading to an accumulation of 6-methylthioinosine monophosphate (6-MTIMP), which has been associated with myelotoxicity in patients treated with azathioprine. The use of pegylated alpha interferons and ribavirin concomitantly with azathioprine should be avoided. In individual cases where the benefit of administering ribavirin concomitantly with azathioprine warrants the potential risk, it is recommended that close hematologic monitoring be done during concomitant azathioprine use to identify signs of myelotoxicity, at which time treatment with these medicines should be stopped (see section 4.4).

No interaction studies have been conducted with Rebetol and other medicinal products, except for peginterferon alfa-2b, interferon alfa-2b and antacids.

Interferon alfa-2b: No pharmacokinetic interactions were noted between Rebetol and peginterferon alfa-2b or interferon alfa-2b in a multiple-dose pharmacokinetic study.

Antacid: The bioavailability of ribavirin 600 mg was decreased by co-administration with an antacid containing magnesium aluminium and simethicone; AUC_tf decreased 14 %. It is possible that the decreased bioavailability in this study was due to delayed transit of ribavirin or modified pH. This interaction is not considered to be clinically relevant.

Nucleoside analogs: Use of nucleoside analogs, alone or in combination with other nucleosides, has resulted in lactic acidosis. Pharmacologically, ribavirin increases phosphorylated metabolites of purine nucleosides in vitro. This activity could potentiate the risk of lactic acidosis induced by purine nucleoside analogs (e.g. didanosine or abacavir). Co-administration of Rebetol and didanosine is not recommended. Reports of mitochondrial toxicity, in particular lactic acidosis and pancreatitis, of which some fatal, have been reported (see section 4.4).

The exacerbation of anaemia due to ribavirin has been reported when zidovudine is part of the regimen used to treat HIV although the exact mechanism remains to be elucidated. The concomitant use of ribavirin with zidovudine is not recommended due to an increased risk of anaemia (see section 4.4). Consideration should be given to replacing zidovudine in a combination anti-retroviral treatment (ART) regimen if this is already established. This would be particularly important in patients with a known history of zidovudine induced anaemia.

Any potential for interactions may persist for up to two months (five half-lives for ribavirin) after cessation of Rebetol therapy due to the long half-life (see section 5.2).

There is no evidence that ribavirin interacts with non-nucleoside reverse transcriptase inhibitors or protease inhibitors.

Conflicting findings are reported in literature on co-administration between abacavir and ribavirin. Some data suggest that HIV/HCV co-infected patients receiving abacavir-containing ART may be at risk of a lower response rate to pegylated interferon/ribavirin therapy. Caution should be exercised when both medicines are co-administered.

Pregnancy

The use of Rebetol is contraindicated during pregnancy.

Fertility

Preclinical data:

- Fertility: In animal studies, ribavirin produced reversible effects on spermatogenesis (see section 5.3).

- Teratogenicity: Significant teratogenic and/or embryocidal potential have been demonstrated for ribavirin in all animal species in which adequate studies have been conducted, occurring at doses as low as one twentieth of the recommended human dose (see section 5.3).

- Genotoxicity: Ribavirin induces genotoxicity (see section 5.3).

Women of childbearing potential/contraception in males and females

Female patients: Rebetol must not be used by females who are pregnant (see sections 4.3 and 5.3). Extreme care must be taken to avoid pregnancy in female patients (see section 5.3). Rebetol therapy must not be initiated until a report of a negative pregnancy test has been obtained immediately prior to initiation of therapy. Females