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Moderate to severe adverse experiences may require modification of the patient's dosage regimen, or in some cases termination of INTRON® A therapy. Because of the fever and other “flu-like” symptoms associated with INTRON A administration, it should be used cautiously in patients with debilitating medical conditions, such as those with a history of pulmonary disease (e.g., chronic obstructive pulmonary disease) or diabetes mellitus prone to ketoacidosis. Caution should also be observed in patients with coagulation disorders (e.g., thrombophlebitis, pulmonary embolism) or severe myelosuppression.
INTRON A therapy should be used cautiously in patients with a history of cardiovascular disease. Those patients with a history of myocardial infarction and/or previous or current arrhythmic disorder who require INTRON A therapy should be closely monitored (see PRECAUTIONS, Laboratory Tests). Cardiovascular adverse experiences, which include hypotension, arrhythmia, or tachycardia of 150 beats per minute or greater, and rarely, cardiomyopathy and myocardial infarction have been observed in some INTRON A-treated patients. Some patients with these adverse events had no history of cardiovascular disease. Transient cardiomyopathy was reported in approximately 2% of the AIDS-Related Kaposi's Sarcoma patients treated with INTRON A. Hypotension may occur during INTRON A administration, or up to 2 days post-therapy, and may require supportive therapy including fluid replacement to maintain intravascular volume.
Supraventricular arrhythmias occurred rarely and appeared to be correlated with preexisting conditions and prior therapy with cardiotoxic agents. These adverse experiences were controlled by modifying the dose or discontinuing treatment, but may require specific additional therapy.
Ischemic and hemorrhagic cerebrovascular events have been observed in patients treated with interferon alpha-based therapies, including INTRON A. 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 alpha-based therapies and these events is difficult to establish.
DEPRESSION AND SUICIDAL BEHAVIOR INCLUDING SUICIDAL IDEATION, SUICIDAL ATTEMPTS, AND COMPLETED SUICIDES, HOMICIDAL IDEATION, AND AGGRESSIVE BEHAVIOR SOMETIMES DIRECTED TOWARDS OTHERS, HAVE BEEN REPORTED IN ASSOCIATION WITH TREATMENT WITH ALPHA INTERFERONS, INCLUDING INTRON A THERAPY. If patients develop psychiatric problems, including clinical depression, it is recommended that the patients be carefully monitored during treatment and in the 6-month follow-up period.
INTRON A should be used with caution in patients with a history of psychiatric disorders. INTRON A therapy should be discontinued for any patient developing severe psychiatric disorder during treatment. Obtundation and coma have also been observed in some patients, usually elderly, treated at higher doses. While these effects are usually rapidly reversible upon discontinuation of therapy, full resolution of symptoms has taken up to 3 weeks in a few severe episodes. If psychiatric symptoms persist or worsen, or suicidal ideation or aggressive behavior towards others is identified, it is recommended that treatment with INTRON A be discontinued and the patient followed, with psychiatric intervention as appropriate. Narcotics, hypnotics, or sedatives may be used concurrently with caution and patients should be closely monitored until the adverse effects have resolved. 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. Cases of encephalopathy have also been observed in some patients, usually elderly, treated with higher doses of INTRON A.
Treatment with interferons may be associated with exacerbated symptoms of psychiatric disorders in patients with co-occurring psychiatric and substance use disorders. If treatment with interferons is initiated in patients with prior history or existence of psychiatric condition or with a history of substance use disorders, treatment considerations should include the need for drug screening and periodic health evaluation, including psychiatric symptom monitoring. Early intervention for reemergence or development of neuropsychiatric symptoms and substance use is recommended.
Bone Marrow Toxicity
INTRON A therapy suppresses bone marrow function and may result in severe cytopenias including aplastic anemia. It is advised that complete blood counts (CBC) be obtained pretreatment and monitored routinely during therapy (see PRECAUTIONS, Laboratory Tests). INTRON A therapy should be discontinued in patients who develop severe decreases in neutrophil (less than 0.5 x 109/L) or platelet counts (less than 25 x 109/L) (see DOSAGE AND ADMINISTRATION, Guidelines for Dose Modification).
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 may be induced or aggravated by treatment with interferon alfa-2b or other alpha interferons. All patients should receive an eye examination at baseline. Patients with preexisting 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. Interferon alfa-2b treatment should be discontinued in patients who develop new or worsening ophthalmologic disorders.
Infrequently, patients receiving INTRON A therapy developed thyroid abnormalities, either hypothyroid or hyperthyroid. The mechanism by which INTRON A may alter thyroid status is unknown. Patients with preexisting thyroid abnormalities whose thyroid function cannot be maintained in the normal range by medication should not be treated with INTRON A. Prior to initiation of INTRON A therapy, serum TSH should be evaluated. Patients developing symptoms consistent with possible thyroid dysfunction during the course of INTRON A therapy should have their thyroid function evaluated and appropriate treatment instituted. Therapy should be discontinued for patients developing thyroid abnormalities during treatment whose thyroid function cannot be normalized by medication. Discontinuation of INTRON A therapy has not always reversed thyroid dysfunction occurring during treatment. Diabetes mellitus has been observed in patients treated with alpha interferons. Patients with these conditions who cannot be effectively treated by medication should not begin INTRON A therapy. Patients who develop these conditions during treatment and cannot be controlled with medication should not continue INTRON A therapy.
Hepatotoxicity, including fatality, has been observed in interferon alpha-treated patients, including those treated with INTRON A. Any patient developing liver function abnormalities during treatment should be monitored closely and if appropriate, treatment should be discontinued.
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 INTRON A or other alpha interferons. Recurrence of respiratory failure has been observed with interferon rechallenge. The etiologic explanation for these pulmonary findings has yet to be established. Any patient developing fever, cough, dyspnea, or other respiratory symptoms should have a chest X-ray taken. If the chest X-ray shows pulmonary infiltrates or there is evidence of pulmonary function impairment, the patient should be closely monitored, and, if appropriate, interferon alpha treatment should be discontinued. While this has been reported more often in patients with chronic hepatitis C treated with interferon alpha, it has also been reported in patients with oncologic diseases treated with interferon alpha.
Rare cases of autoimmune diseases including thrombocytopenia, vasculitis, Raynaud's phenomenon, rheumatoid arthritis, lupus erythematosus, and rhabdomyolysis have been observed in patients treated with alpha interferons, including patients treated with INTRON A. In very rare cases the event resulted in fatality. The mechanism by which these events developed and their relationship to interferon alpha therapy is not clear. Any patient developing an autoimmune disorder during treatment should be closely monitored and, if appropriate, treatment should be discontinued.
The powder formulations of this product contain albumin, a derivative of human blood. Based on effective donor screening and product manufacturing processes, it carries an extremely remote risk for transmission of viral diseases. A theoretical risk for transmission of Creutzfeldt-Jakob disease (CJD) also is considered extremely remote. No cases of transmission of viral diseases or CJD have ever been identified for albumin.
AIDS-Related Kaposi's Sarcoma
INTRON A therapy should not be used for patients with rapidly progressive visceral disease (see CLINICAL PHARMACOLOGY). Also of note, there may be synergistic adverse effects between INTRON A and zidovudine. Patients receiving concomitant zidovudine have had a higher incidence of neutropenia than that expected with zidovudine alone. Careful monitoring of the WBC count is indicated in all patients who are myelosuppressed and in all patients receiving other myelosuppressive medications. The effects of INTRON A when combined with other drugs used in the treatment of AIDS-related disease are unknown.
Chronic Hepatitis C And Chronic Hepatitis B
Patients with decompensated liver disease, autoimmune hepatitis or a history of autoimmune disease, and patients who are immunosuppressed transplant recipients should not be treated with INTRON A. There are reports of worsening liver disease, including jaundice, hepatic encephalopathy, hepatic failure, and death following INTRON A therapy in such patients. Therapy should be discontinued for any patient developing signs and symptoms of liver failure.
Chronic hepatitis B patients with evidence of decreasing hepatic synthetic functions, such as decreasing albumin levels or prolongation of prothrombin time, who nevertheless meet the entry criteria to start therapy, may be at increased risk of clinical decompensation if a flare of aminotransferases occurs during INTRON A treatment. In such patients, if increases in ALT occur during INTRON A therapy for chronic hepatitis B, they should be followed carefully, including close monitoring of clinical symptomatology and liver function tests including ALT, prothrombin time, alkaline phosphatase, albumin, and bilirubin. In considering these patients for INTRON A therapy, the potential risks must be evaluated against the potential benefits of treatment.
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 pegylated interferon alfa-2a as compared to telbivudine alone. The safety and efficacy of telbivudine in combination with interferons for the treatment of chronic hepatitis B has not been demonstrated.
Use With Ribavirin (see also REBETOL® prescribing information)
REBETOL may cause birth defects and/or death of the unborn child. REBETOL therapy should not be started until a report of a negative pregnancy test has been obtained immediately prior to planned initiation of therapy. Patients should use at least two forms of contraception and have monthly pregnancy tests (see CONTRAINDICATIONS and PATIENT INFORMATION).
Combination treatment with INTRON A and REBETOL was associated with hemolytic anemia. Hemoglobin less than 10 g/dL was observed in approximately 10% of adult and pediatric patients in clinical trials. Anemia occurred within 1 to 2 weeks of initiation of ribavirin therapy. Combination treatment with INTRON A and REBETOL should not be used in patients with creatinine clearance less than 50 mL/min. See REBETOL prescribing information for additional information.
Acute serious hypersensitivity reactions (e.g., urticaria, angioedema, bronchoconstriction, anaphylaxis) have been observed rarely in INTRON® A-treated patients; if such an acute reaction develops, the drug should be discontinued immediately and appropriate medical therapy instituted. Transient rashes have occurred in some patients following injection, but have not necessitated treatment interruption.
While fever may be related to the flu-like syndrome reported commonly in patients treated with interferon, other causes of persistent fever should be ruled out.
There have been reports of interferon, including INTRON A, exacerbating preexisting psoriasis and sarcoidosis as well as development of new sarcoidosis. Therefore, INTRON A therapy should be used in these patients only if the potential benefit justifies the potential risk.
Variations in dosage, routes of administration, and adverse reactions exist among different brands of interferon. Therefore, do not use different brands of interferon in any single treatment regimen.
Elevated triglyceride levels have been observed in patients treated with interferons, including INTRON A therapy. Elevated triglyceride levels should be managed as clinically appropriate. Hypertriglyceridemia may result in pancreatitis. Discontinuation of INTRON A therapy should be considered for patients with persistently elevated triglycerides (e.g., triglycerides greater than 1000 mg/dL) associated with symptoms of potential pancreatitis, such as abdominal pain, nausea, or vomiting.
Information for Patients
Patients receiving INTRON A alone or in combination with REBETOL® should be informed of the risks and benefits associated with treatment and should be instructed on proper use of the product. To supplement your discussion with a patient, you may wish to provide patients with a copy of the MEDICATION GUIDE.
Patients should be informed of, and advised to seek medical attention for, symptoms indicative of serious adverse reactions associated with this product. Such adverse reactions may include depression (suicidal ideation), cardiovascular (chest pain), ophthalmologic toxicity (decrease in/or loss of vision), pancreatitis or colitis (severe abdominal pain), and cytopenias (high persistent fevers, bruising, dyspnea). Patients should be advised that some side effects such as fatigue and decreased concentration might interfere with the ability to perform certain tasks. Patients who are taking INTRON A in combination with REBETOL must be thoroughly informed of the risks to a fetus. Female patients and female partners of male patients must be told to use two forms of birth control during treatment and for six months after therapy is discontinued (see Medication Guide).
Patients should be advised to remain well hydrated during the initial stages of treatment and that use of an antipyretic may ameliorate some of the flu-like symptoms.
If a decision is made to allow a patient to self-administer INTRON A, they should be instructed, based on their treatment, if they should inject a dose of INTRON® A subcutaneously or intramuscularly. If it is too difficult for them to inject themselves, they should be instructed to ask someone who has been trained to give the injection to them. Patients should be instructed on the importance of site selection for self-administering the injection, as well as the importance on rotating the injection sites. A puncture resistant container for the disposal of needles and syringes should be supplied. Patients self-administering INTRON A should be instructed on the proper disposal of needles and syringes and cautioned against reuse.
Patients should be instructed that the Sterile Water for Injection vial supplied with Intron A Powder for Injection contains an excess amount of diluent (5 mL) and only 1 mL should be withdrawn to reconstitute Intron A Powder for Injection. The vial of Sterile Water for Injection is intended for single use only. Discard the unused portion of sterile water. Do not save or reuse.
Dental and Periodontal Disorders
Dental and periodontal disorders have been reported in patients receiving ribavirin and interferon 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 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.
In addition to those tests normally required for monitoring patients, the following laboratory tests are recommended for all patients on INTRON A therapy, prior to beginning treatment and then periodically thereafter.
- Standard hematologic tests — including hemoglobin, complete and differential white blood cell counts, and platelet count.
- Blood chemistries — electrolytes, liver function tests, and TSH.
Those patients who have preexisting cardiac abnormalities and/or are in advanced stages of cancer should have electrocardiograms taken prior to and during the course of treatment.
Mild-to-moderate leukopenia and elevated serum liver enzyme (SGOT) levels have been reported with intralesional administration of INTRON A (see ADVERSE REACTIONS); therefore, the monitoring of these laboratory parameters should be considered.
Baseline chest X-rays are suggested and should be repeated if clinically indicated.
For malignant melanoma patients, differential WBC count and liver function tests should be monitored weekly during the induction phase of therapy and monthly during the maintenance phase of therapy.
For specific recommendations in chronic hepatitis C and chronic hepatitis B, see INDICATIONS AND USAGE.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
Studies with INTRON A have not been performed to determine carcinogenicity.
Interferon may impair fertility. In studies of interferon administration in nonhuman primates, menstrual cycle abnormalities have been observed. Decreases in serum estradiol and progesterone concentrations have been reported in women treated with human leukocyte interferon.12 Therefore, fertile women should not receive INTRON A therapy unless they are using effective contraception during the therapy period. INTRON A therapy should be used with caution in fertile men.
Mutagenicity studies have demonstrated that INTRON A is not mutagenic.
Studies in mice (0.1, 1.0 million IU/day), rats (4, 20, 100 million IU/kg/day), and cynomolgus monkeys (1.1 million IU/kg/day; 0.25, 0.75, 2.5 million IU/kg/day) injected with INTRON A for up to 9 days, 3 months, and 1 month, respectively, have revealed no evidence of toxicity. However, in cynomolgus monkeys (4, 20, 100 million IU/kg/day) injected daily for 3 months with INTRON A, toxicity was observed at the mid and high doses and mortality was observed at the high dose.
However, due to the known species-specificity of interferon, the effects in animals are unlikely to be predictive of those in man.
INTRON A in combination with REBETOL should be used with caution in fertile men. See the REBETOL prescribing information for additional information.
Pregnancy Category C INTRON A has been shown to have abortifacient effects in Macaca mulatta (rhesus monkeys) at 15 and 30 million IU/kg (estimated human equivalent of 5 and 10 million IU/kg, based on body surface area adjustment for a 60-kg adult). There are no adequate and well-controlled studies in pregnant women. INTRON A therapy should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Pregnancy Category X applies to combination treatment with INTRON A and REBETOL (see CONTRAINDICATIONS). See REBETOL prescribing information for additional information. Significant teratogenic and/or embryocidal effects have been demonstrated in all animal species exposed to ribavirin. REBETOL therapy is contraindicated in women who are pregnant and in the male partners of women who are pregnant. See CONTRAINDICATIONS and the REBETOL prescribing information.
Ribavirin Pregnancy Registry: A Ribavirin Pregnancy Registry has been established to monitor maternal-fetal outcomes of pregnancies in female patients and female partners of male patients exposed to ribavirin during treatment and for 6 months following cessation of treatment. Physicians and patients are encouraged to report such cases by calling 1-800-593-2214.
It is not known whether this drug is excreted in human milk. However, studies in mice have shown that mouse interferons are excreted into the milk. Because of the potential for serious adverse reactions from the drug in nursing infants, a decision should be made whether to discontinue nursing or to discontinue INTRON A therapy, taking into account the importance of the drug to the mother.
Safety and effectiveness in pediatric patients have not been established for indications other than chronic hepatitis B and chronic hepatitis C. Chronic Hepatitis B Safety and effectiveness in pediatric patients ranging in age from 1 to 17 years have been established based upon one controlled clinical trial (see CLINICAL PHARMACOLOGY, INDICATIONS AND USAGE, and DOSAGE AND ADMINISTRATION, Chronic Hepatitis B Pediatrics).
Chronic Hepatitis C Safety and effectiveness in pediatric patients ranging in age from 3 to 16 years have been established based upon clinical studies in 118 patients. See REBETOL prescribing information for additional information. Suicidal ideation or attempts occurred more frequently among pediatric patients compared to adult patients (2.4% versus 1%) during treatment and off-therapy follow-up (see WARNINGS, Neuropsychiatric Disorders). 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 suggests that combination therapy may induce a growth inhibition that results in reduced final adult height in some patients (see ADVERSE REACTIONS, Chronic Hepatitis C Pediatrics).
In all clinical studies of INTRON A, including studies as monotherapy and in combination with REBETOL (ribavirin USP) Capsules, only a small percentage of the subjects were aged 65 and over. These numbers were too few to determine if they respond differently from younger subjects except for the clinical trials of INTRON A in combination with REBETOL, where elderly subjects had a higher frequency of anemia (67%) than did younger patients (28%).
In a database consisting of clinical study and postmarketing reports for various indications, cardiovascular adverse events and confusion were reported more frequently in elderly patients receiving INTRON A therapy compared to younger patients.
In general, INTRON A therapy should be administered to elderly patients cautiously, reflecting the greater frequency of decreased hepatic, renal, bone marrow, and/or cardiac function and concomitant disease or other drug therapy. INTRON A is known to be substantially excreted by the kidney, and the risk of adverse reactions to INTRON A may be greater in patients with impaired renal function. Because elderly patients often have decreased renal function, patients should be carefully monitored during treatment, and dose adjustments made based on symptoms and/or laboratory abnormalities (see CLINICAL PHARMACOLOGY and DOSAGE AND ADMINISTRATION).This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 9/25/2014
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