PEGINTERFERON ALFA-2A Drug Interactions: What You Need to Know

INTERACTIONS Drugs metabolized by CYP1A2: monitor for increased serum levels of theophylline and adjust dose accordingly ( 7.2 ) Methadone: monitor for signs and symptoms of methadone toxicity ( 7.3 ) Nucleoside analogues: closely monitor for toxicities. Reduce or discontinue the dose of PEGASYS or ribavirin or both should the events worsen ( 7.4 ) Zidovudine: monitor for worsening neutropenia and/or anemia with PEGASYS and/or ribavirin ( 7.4 )

7.1 Drugs Metabolized by Cytochrome P450 There was no effect on the pharmacokinetics of representative drugs metabolized by CYP 2C9, CYP 2C19, CYP 2D6 or CYP 3A4. Treatment with PEGASYS once weekly for 4 weeks in healthy subjects was associated with an inhibition of P450 1A2 and a 25% increase in theophylline AUC.

7.2 Theophylline Treatment with PEGASYS once weekly for 4 weeks in healthy subjects was associated with an inhibition of P450 1A2 and a 25% increase in theophylline AUC. Theophylline serum levels should be monitored and appropriate dose adjustments considered for patients given both theophylline and PEGASYS.

7.3 Methadone In a PK study of HCV subjects concomitantly receiving methadone, treatment with PEGASYS once weekly for 4 weeks was associated with methadone levels that were 10% to 15% higher than at baseline. The clinical significance of this finding is unknown; however, patients should be monitored for the signs and symptoms of methadone toxicity. The pharmacokinetics of concomitant administration of methadone and PEGASYS were evaluated in 24 PEGASYS naïve CHC subjects (15 male, 9 female) who received 180 mcg PEGASYS subcutaneously weekly. All subjects were on stable methadone maintenance therapy (median dose 95 mg, range 30 mg to 150 mg) prior to receiving PEGASYS. Mean methadone PK parameters were 10% to 15% higher after 4 weeks of PEGASYS treatment as compared to baseline. Methadone did not significantly alter the PK of PEGASYS as compared to a PK study of 6 chronic hepatitis C subjects not receiving methadone.

7.4 Nucleoside Analogues NRTIs In Study 7 among the CHC/HIV coinfected cirrhotic subjects receiving NRTIs cases of hepatic decompensation (some fatal) were observed <span class="opacity-50 text-xs">[see Warnings and Precautions (5.9) ]</span> . Patients receiving PEGASYS/ribavirin in combination with other HCV antiviral drugs and NRTIs should be closely monitored for treatment associated toxicities. Physicians should refer to prescribing information for other HCV antiviral drugs and the respective NRTIs for guidance regarding toxicity management. In addition, dose reduction or discontinuation of PEGASYS, ribavirin or both, should also be considered if worsening toxicities are observed <span class="opacity-50 text-xs">[see Warnings and Precautions (5.3 , 5.9) and Dosage and Administration (2.6) ]</span> .

Zidovudine In Study

7, subjects who were administered zidovudine in combination with PEGASYS/ribavirin developed severe neutropenia (ANC less than 500 cells/mm 3 ) and severe anemia (hemoglobin less than 8 g/dL) more frequently than similar subjects not receiving zidovudine (neutropenia 15% vs. 9%) (anemia 5% vs. 1%). Discontinuation of zidovudine should be considered as medically appropriate. Dose reduction or discontinuation of PEGASYS, ribavirin or both should also be considered if worsening clinical toxicities are observed, including hepatic decompensation (e.g., Child-Pugh greater than 6). Refer to the prescribing information for specific HCV antiviral drugs used in combination with PEGASYS for information on drug interaction potential.

PEGASYS is contraindicated in patients with: Known hypersensitivity reactions such as urticaria, angioedema, bronchoconstriction, anaphylaxis, or Stevens-Johnson syndrome to alpha interferons, including PEGASYS, or any of its components. Autoimmune hepatitis Hepatic decompensation (Child-Pugh score greater than 6 [class B and C]) in cirrhotic patients before treatment Hepatic decompensation with Child-Pugh score greater than or equal to 6 in cirrhotic CHC patients coinfected with HIV before treatment PEGASYS is contraindicated in neonates and infants because it contains benzyl alcohol. Benzyl alcohol is associated with an increased incidence of neurologic and other complications which are sometimes fatal in neonates and infants. When PEGASYS is used in combination with other HCV antiviral drugs, the contraindications applicable to those agents are applicable to combination therapies. PEGASYS combination treatment with ribavirin is contraindicated in women who are pregnant and men whose female partners are pregnant [See Warnings and Precautions (5.1) and Use in Specific Populations (8.1) ]. Refer to the prescribing information of the other HCV antiviral drugs, including ribavirin, for a list of their contraindications. Autoimmune hepatitis ( 4 ) Hepatic decompensation in patients with cirrhosis ( 4 ) Use in neonates/infants ( 4 ) Known hypersensitivity reactions such as urticaria, angioedema, bronchoconstriction and anaphylaxis to alpha interferons or any component of the product ( 4 ) Additional contraindications for use with other HCV antiviral drugs: When used in combination with other HCV antiviral drugs, all contraindications also apply to PEGASYS combination therapy ( 4 ) Ribavirin is contraindicated in pregnant women and men whose female partners are pregnant ( 4 , 8.1 )

AND PRECAUTIONS Refer to the prescribing information of the other HCV antiviral drugs, including ribavirin, for their Warnings and Precautions. Use with ribavirin Birth defects and fetal death: patients must have a negative pregnancy test prior to therapy, use 2 forms of effective contraception, and have monthly pregnancy tests ( 5.1 )

Pegasys

Clinically Significant Adverse Reactions or Risks Patients exhibiting the following events should be closely monitored and may require dose reduction or discontinuation of therapy: Neuropsychiatric reactions ( 5.2 ) Cardiovascular disorders ( 5.3 ) Bone marrow suppression ( 5.4 ) Autoimmune and endocrine disorders (including thyroid disorders; hyperglycemia) ( 5.5 , 5.6 ) Ophthalmologic disorders ( 5.7 ) Cerebrovascular disorders ( 5.8 ) Hepatic decompensation in cirrhotic patients. Exacerbation of hepatitis during hepatitis B treatment ( 5.9 ) Pulmonary disorders ( 5.10 ) Infections (bacterial, viral, fungal) ( 5.11 ) Colitis and pancreatitis ( 5.12 , 5.13 ) Hypersensitivity and serious skin reactions including Stevens-Johnson syndrome ( 5.14 ) Growth impairment with combination therapy in pediatric patients ( 5.15 ) Peripheral neuropathy when used in combination with telbivudine ( 5.16 )

5.1 Pregnancy: Use with ribavirin Ribavirin may cause birth defects and/or death of the exposed fetus. Patients must avoid pregnancy (female patients or female partners of male patients) while taking PEGASYS and ribavirin combination therapy. Ribavirin therapy should not be started unless a confirmed negative pregnancy test has been obtained immediately prior to initiation of therapy. Women of childbearing potential and men must use two forms of effective contraception during treatment and for at least 6 months after treatment has concluded. Routine monthly pregnancy tests must be performed during this time <span class="opacity-50 text-xs">[see Contraindications (4) , Patient Counseling Information (17) and ribavirin labeling]</span> .

5.2 Neuropsychiatric Reactions Life-threatening or fatal neuropsychiatric reactions may manifest in all patients receiving therapy with PEGASYS and include suicide, suicidal ideation, homicidal ideation, depression, relapse of drug addiction, and drug overdose. These reactions may occur in patients with and without previous psychiatric illness. PEGASYS should be used with extreme caution in all patients who report a history of depression. Neuropsychiatric adverse events observed with alpha interferon treatment include aggressive behavior, psychoses, hallucinations, bipolar disorders, and mania. Physicians should monitor all patients for evidence of depression and other psychiatric symptoms. Patients should be advised to report any sign or symptom of depression or suicidal ideation to their prescribing physicians. In severe cases, therapy should be stopped immediately and psychiatric intervention instituted <span class="opacity-50 text-xs">[see Boxed Warning , Adverse Reactions (6.1) and Dosage and Administration (2.6) ]</span> .

5.3 Cardiovascular Disorders Hypertension, supraventricular arrhythmias, chest pain, and myocardial infarction have been observed in patients treated with PEGASYS. PEGASYS should be administered with caution to patients with pre-existing cardiac disease. Because cardiac disease may be worsened by ribavirin-induced anemia, patients with a history of significant or unstable cardiac disease should not receive PEGASYS/ribavirin <span class="opacity-50 text-xs">[see ribavirin prescribing information]</span> .

5.4 Bone Marrow Suppression PEGASYS suppresses bone marrow function and may result in severe cytopenias. Ribavirin may potentiate the neutropenia and lymphopenia induced by alpha interferons including PEGASYS. Very rarely, alpha interferons may be associated with aplastic anemia. It is advised that complete blood counts (CBC) be obtained pre-treatment and monitored routinely during therapy <span class="opacity-50 text-xs">[see ribavirin prescribing information]</span> . PEGASYS/ribavirin should be used with caution in patients with baseline neutrophil counts less than 1,500 cells/mm 3 , with baseline platelet counts less than 90,000 cells/mm 3 or baseline hemoglobin less than 10 g/dL. PEGASYS therapy should be discontinued, at least temporarily, in patients who develop severe decreases in neutrophil and/or platelet counts <span class="opacity-50 text-xs">[see Dosage and Administration (2.6) ]</span> . Severe neutropenia and thrombocytopenia occur with a greater incidence in HIV coinfected patients than monoinfected patients and may result in serious infections or bleeding <span class="opacity-50 text-xs">[see Adverse Reactions (6.1) ]</span> . Pancytopenia (marked decreases in RBCs, neutrophils and platelets) and bone marrow suppression have been reported in the literature to occur within 3 to 7 weeks after the concomitant administration of pegylated interferon/ribavirin and azathioprine. In this limited number of patients (n=8), myelotoxicity was reversible within 4 to 6 weeks upon withdrawal of both HCV antiviral therapy and concomitant azathioprine and did not recur upon reintroduction of either treatment alone. PEGASYS, ribavirin, and azathioprine should be discontinued for pancytopenia, and pegylated interferon/ribavirin should not be re-introduced with concomitant azathioprine.

5.5 Autoimmune Disorders Development or exacerbation of autoimmune disorders including myositis, hepatitis, thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura, psoriasis, rheumatoid arthritis, interstitial nephritis, thyroiditis, and systemic lupus erythematosus have been reported in patients receiving alpha interferon. PEGASYS should be used with caution in patients with autoimmune disorders <span class="opacity-50 text-xs">[see Boxed Warning ]</span> .

5.6 Endocrine Disorders PEGASYS causes or aggravates hypothyroidism and hyperthyroidism. Hyperglycemia, hypoglycemia, and diabetes mellitus have been observed to develop in patients treated with PEGASYS. Patients with these conditions at baseline who cannot be effectively treated by medication should not begin PEGASYS therapy. Patients who develop these conditions during treatment and cannot be controlled with medication may require discontinuation of PEGASYS therapy.

5.7 Ophthalmologic Disorders Decrease or loss of vision, retinopathy including macular edema, retinal artery or vein thrombosis, retinal hemorrhages and cotton wool spots, optic neuritis, papilledema and serous retinal detachment are induced or aggravated by treatment with PEGASYS or other alpha interferons. All patients should receive an eye examination at baseline. Patients with pre-existing ophthalmologic disorders (e.g., diabetic or hypertensive retinopathy) should receive periodic ophthalmologic exams during interferon alpha treatment. Any patient who develops ocular symptoms should receive a prompt and complete eye examination. PEGASYS treatment should be discontinued in patients who develop new or worsening ophthalmologic disorders.

5.8 Cerebrovascular Disorders Ischemic and hemorrhagic cerebrovascular events have been observed in patients treated with interferon alfa-based therapies, including PEGASYS. Events occurred in patients with few or no reported risk factors for stroke, including patients less than 45 years of age. Because these are spontaneous reports, estimates of frequency cannot be made and a causal relationship between interferon alfa-based therapies and these events is difficult to establish <span class="opacity-50 text-xs">[see Boxed Warning ]</span> .

5.9 Hepatic Failure and Hepatitis Exacerbations Chronic hepatitis C (CHC) patients with cirrhosis may be at risk of hepatic decompensation and death when treated with alpha interferons, including PEGASYS. 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

7 [see Clinical Studies (14.3) ] , among 129 CHC/HIV cirrhotic subjects receiving HAART, 14 (11%) of these subjects across all treatment arms developed hepatic decompensation resulting in 6 deaths.

All

14 subjects were on NRTIs, including stavudine, didanosine, abacavir, zidovudine, and lamivudine. These small numbers of patients do not permit discrimination between specific NRTIs for the associated risk. During treatment, patients' clinical status and hepatic function should be closely monitored, and PEGASYS/ribavirin treatment should be immediately discontinued in patients with hepatic decompensation [see Contraindications (4) ] . Exacerbations of hepatitis during hepatitis B therapy are not uncommon and are characterized by transient and potentially severe increases in serum ALT. Chronic hepatitis B subjects experienced transient acute exacerbations (flares) of hepatitis B (ALT elevation greater than 10-fold higher than the upper limit of normal) during PEGASYS treatment (12% and 18%) and post-treatment (7% and 12%) in HBeAg-negative and HBeAg-positive subjects, respectively. Marked transaminase flares while on PEGASYS therapy have been accompanied by other liver test abnormalities. Patients experiencing ALT flares should receive more frequent monitoring of liver function. PEGASYS dose reduction should be considered in patients experiencing transaminase flares. If ALT increases are progressive despite reduction of PEGASYS dose or are accompanied by increased bilirubin or evidence of hepatic decompensation, PEGASYS should be immediately discontinued [see Adverse Reactions (6.1) and Dosage and Administration (2.6) ] .

5.10 Pulmonary Disorders Dyspnea, pulmonary infiltrates, pneumonia, bronchiolitis obliterans, interstitial pneumonitis, pulmonary hypertension and sarcoidosis, some resulting in respiratory failure and/or patient deaths, may be induced or aggravated by PEGASYS or alpha interferon therapy. Recurrence of respiratory failure has been observed with interferon rechallenge. PEGASYS combination treatment should be suspended in patients who develop pulmonary infiltrates or pulmonary function impairment. Patients who resume interferon treatment should be closely monitored.

5.11 Infections While fever may be associated with the flu-like syndrome reported commonly during interferon therapy, other causes of high or persistent fever must be ruled out, particularly in patients with neutropenia. Serious and severe infections (bacterial, viral, or fungal), some fatal, have been reported during treatment with alpha interferons including PEGASYS. Appropriate anti-infective therapy should be started immediately and discontinuation of therapy should be considered <span class="opacity-50 text-xs">[see Boxed Warning ]</span> .

5.12 Colitis Ulcerative and hemorrhagic/ischemic colitis, sometimes fatal, have been observed within 12 weeks of starting alpha interferon treatment. Abdominal pain, bloody diarrhea, and fever are the typical manifestations of colitis. PEGASYS should be discontinued immediately if these symptoms develop. The colitis usually resolves within 1 to 3 weeks of discontinuation of alpha interferon.

5.13 Pancreatitis Pancreatitis, sometimes fatal, has occurred during alpha interferon and ribavirin treatment. PEGASYS/ribavirin should be suspended if symptoms or signs suggestive of pancreatitis are observed. PEGASYS/ribavirin should be discontinued in patients diagnosed with pancreatitis.

5.14 Hypersensitivity Severe acute hypersensitivity reactions (e.g., urticaria, angioedema, bronchoconstriction, and anaphylaxis) have been observed during alpha interferon and ribavirin therapy. If such reaction occurs, therapy with PEGASYS/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 reported in patients receiving PEGASYS with and without ribavirin. Patients developing signs or symptoms of severe skin reactions must discontinue therapy <span class="opacity-50 text-xs">[see Adverse Reactions (6.2) ]</span> .

5.15 Impact on Growth in Pediatric Patients Growth inhibition was observed in CHC pediatric subjects 5 to 17 years of age during combination therapy for up to 48 weeks with PEGASYS plus ribavirin. At the end of treatment, 43% of subjects were more than 15 percentiles below their baseline weight curve, and 25% of subjects were more than 15 percentiles below their baseline height curve. At the end of 2 years follow-up after treatment, most subjects had returned to baseline normative curve percentiles for weight and height; 16% of subjects were more than 15 percentiles below their baseline weight curve and 11% were more than 15 percentiles below their baseline height curve. The available longer-term data on subjects who were followed up to 6 years post-treatment are too limited to determine the risk of reduced adult height in some patients <span class="opacity-50 text-xs">[see Clinical Trials Experience (6.1) ]</span>. Growth inhibition was also observed in CHB pediatric subjects 3 to 17 years of age during therapy with PEGASYS lasting up to 48 weeks.

At Week

48 of treatment 13% of subjects were more than 15 percentiles below their baseline weight curve and 6% were more than 15 percentiles below their baseline height curve.

At

24 weeks after the end of treatment, 11% of subjects were more than 15 percentiles below their baseline weight curve and 12% were more than 15 percentiles below their baseline height curve.

At

5 years post-treatment the percentage of subjects with decrease of more than 15 percentiles from baseline was 29% for weight and 18% for height. [see Clinical Trials Experience (6.1) ].

5.16 Peripheral Neuropathy Peripheral neuropathy has been reported when alpha interferons were given in combination with telbivudine. In one clinical trial, an increased risk and severity of peripheral neuropathy was observed with the combination use of telbivudine and PEGASYS as compared to telbivudine alone. The safety and efficacy of telbivudine in combination with interferons for the treatment of CHB have not been demonstrated.

5.17 Laboratory Tests Before beginning PEGASYS or PEGASYS combination therapy, standard hematological and biochemical laboratory tests are recommended for all patients. Pregnancy screening for women of childbearing potential must be performed. Patients who have pre-existing cardiac abnormalities should have electrocardiograms administered before treatment with PEGASYS/ribavirin. 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. In adult clinical studies, the CBC (including hemoglobin level and white blood cell and platelet counts) and chemistries (including liver function tests and uric acid) were measured at 1, 2, 4, 6, and 8 weeks, and then every 4 to 6 weeks or more frequently if abnormalities were found. In a pediatric clinical trial, hematological and chemistry assessments were at 1, 3, 5, and 8 weeks, then every 4 weeks. Thyroid stimulating hormone (TSH) was measured every 12 weeks. Monthly pregnancy testing should be performed during combination therapy and for 6 months after discontinuing therapy. The entrance criteria used for the clinical studies of PEGASYS may be considered as a guideline to acceptable baseline values for initiation of treatment: Platelet count greater than or equal to 90,000 cells/mm 3 (as low as 75,000 cells/mm 3 in HCV subjects with cirrhosis or 70,000 cells/mm 3 in subjects with CHC and HIV) Absolute neutrophil count (ANC) greater than or equal to 1,500 cells/mm 3 Serum creatinine concentration less than 1.5 × upper limit of normal TSH and T 4 within normal limits or adequately controlled thyroid function CD4+ cell count greater than or equal to 200 cells/mm 3 or CD4+ cell count greater than or equal to 100 cells/mm 3 but less than 200 cells/mm 3 and HIV-1 RNA less than 5,000 copies/mL in subjects coinfected with HIV Hemoglobin greater than or equal to 12 g/dL for women and greater than or equal to 13 g/dL for men in CHC monoinfected subjects Hemoglobin greater than or equal to 11 g/dL for women and greater than or equal to 12 g/dL for men in subjects with CHC and HIV