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Indications and Dosage
Parenteral
Multiple sclerosis Adult: Dose depends on the formulation used. As Avonex®: 6 million units (30 mcg) once wkly via IM inj. As Rebif®: Dose is slowly titrated upwards over 4 wk. Given via SC inj. Initially, 8.8 mcg 3 times wkly for 2 wk, followed by 22 mcg 3 times wkly for 2 wk and finally to 44 mcg 3 times wkly. For patients who are unable to tolerate higher doses, may start with 4.4 mcg 3 times wkly for 2 wk, followed by 11 mcg 3 times wkly for 2 wk, then to 22 mcg 3 times wkly for 2 wk.
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Hepatic Impairment
As Rebif®: Reduce dose by 20-50% if there is leukopenia or increase in LFTs until toxicity resolves.
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Special Precautions
Caution when used in patients with depression or psychiatric disorders, epilepsy or other CNS diseases, poorly controlled thyroid dysfunction, pulmonary disease, DM, renal or hepatic impairment, cardiac disorders, myelosuppression, auto-immune diseases, coagulation disorders, or a history of these conditions. Monitor blood counts especially in patients at high risk of myelosuppression. Eye examination should be conducted prior to starting treatment and regularly thereafter. Monitor hepatic and renal function regularly. Treatment should be discontinued in patients with chronic hepatitis who develop liver decompensation. May affect ability to drive or operate machinery. Pregnancy.
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Adverse Reactions
Depression, flu-like symptom complex, inj site reactions, leukopenia, increased liver enzymes, asthenia, hypertonia and myasthenia. May also cause menstrual irregularities.
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IM/Parenteral/SC: C
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Overdosage
Symptoms: CNS depression, obtundation, flu-like symptoms, myelosuppression. Treatment is symptomatic and supportive.
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Drug Interactions
May increase the adverse effects (especially granulocytopenia) of ACE inhibitors. Increased risk of hepatic injury when used with hepatotoxic drugs. May increase serum levels of theophylline derivatives. May increase the anticoagulant effects of warfarin. May decrease the metabolism of zidovudine.
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Action
Description: Interferon beta 1a alters the expression and response to surface antigens and can improve immune cell activities. It has antiviral and immunomodulating properties.
Pharmacokinetics: Absorption: Not absorbed from the GI tract. About 50% of an IM or SC dose is absorbed. Excretion: Elimination half-life: About 10 hr. |
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Storage
For Avonex®: Prefilled syringe: Store at 2-8°C. May store at ≤25°C for up to 7 days if there is no refrigeration facility. Vial: Store unreconstituted vial at 2-8°C. May store at 25°C for up to 30 days if there is no refrigeration facility. Reconstituted solution should be used immediately, but may be stored up to 6 hr at 2-8°C. For Rebif®: Store at 2-8°C. May be stored at ≤25°C for up to 30 days if protected from heat and light.
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