interferon beta-1a

General

Pronunciation:
in-ter-feer-on bay-ta won-aye

Trade Name(s)

• Avonex
• Rebif

Ther. Class.

anti-multiple sclerosis agents

immune modifiers

Pharm. Class.

interferons

Indications

Relapsing forms of multiple sclerosis, including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease.

Action

• Antiviral and immunoregulatory properties produced by interacting with specific receptor sites on cell surfaces may explain beneficial effects.
• Produced by recombinant DNA technology.

Therapeutic Effect(s):

Reduce incidence of relapse (neurologic dysfunction) and slow physical disability.

Pharmacokinetics

Absorption: 50% absorbed following SUBQ administration.

Distribution: Unknown.

Metabolism and Excretion: Unknown.

Half-life: 69 hr (SUBQ), 10 hr (IM).

TIME/ACTION PROFILE (plasma concentrations)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity to natural or recombinant interferon beta.

Use Cautiously in:

• History of suicide attempt or depression;
• History of seizures;
• Cardiovascular disease;
• Liver disease;
• History of alcohol abuse;
• OB:   Use during pregnancy only if potential maternal benefit justifies potential fetal risk;
• Lactation:  Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
• Rep:  Women of reproductive potential;
• Pedi:   Safety and effectiveness not established in children.

Adverse Reactions/Side Effects

CV: chest pain, heart failure

Derm: alopecia, ERYTHEMA MULTIFORME, ↑ sweating, rash, STEVENS-JOHNSON SYNDROME

EENT: sinusitis, vision abnormalities

Endo: hyperthyroidism, hypothyroidism

GI: abdominal pain, nausea, autoimmune hepatitis, dry mouth, ↑ liver enzymes

GU: urinary tract infection, polyuria, spontaneous abortion, urinary incontinence

Hemat: neutropenia, anemia, HEMOLYTIC UREMIC SYNDROME, thrombocytopenia, THROMBOTIC THROMBOCYTOPENIC PURPURA

Local: injection-site reactions, injection site necrosis

MS: myalgia, pain, arthralgia, back pain, muscle spasm

Neuro: depression, dizziness, fatigue, headache, drowsiness, incoordination, rigors, SEIZURES, suicidal ideation

Resp: PULMONARY ARTERIAL HYPERTENSION, upper respiratory tract infection

Misc: chills, fever, flu-like symptoms, HYPERSENSITIVITY REACTIONS (including anaphylaxis)

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

• ↑ myelosuppression may occur with other myelosuppressives including  antineoplastics.
• Concurrent use of  hepatotoxic agents  may ↑ the risk of hepatotoxicity (↑ liver enzymes).

Drug-Natural Products:

Avoid concomitant use with immmunomodulating natural products such as  astragalus,  echinacea, and  melatonin .

Route/Dosage

Avonex

IM (Adults): 30 mcg once weekly.

Rebif

SUBQ (Adults): Target dose of 22 mcg 3 times/wk –Start with 4.4 mcg 3 times/wk for 2 wk, then ↑ to 11 mcg 3 times/wk for 2 wk, then ↑ to maintenance dose of 22 mcg 3 times/wk; Target dose of 44 mcg 3 times/wk –Start with 8.8 mcg 3 times/wk for 2 wk, then ↑ to 22 mcg 3 times/wk for 2 wk, then ↑ to maintenance dose of 44 mcg 3 times/wk.

Availability

Avonex

Solution for injection (prefilled syringes and prefilled pens): 30 mcg/0.5 mL

Rebif

Solution for injection (prefilled syringes): 22 mcg/0.5 mL, 44 mcg/0.5 mL, titration pack of 6 syringes prefilled with 8.8 mcg/0.2 mL and 6 syringes prefilled with 22 mcg/0.5 mL

Assessment

• Assess frequency of exacerbations of symptoms of multiple sclerosis periodically during therapy.
• Monitor for injection site abscesses, cellulitis and injection site necrosis; may require hospitalization for surgical drainage and intravenous antibiotics.
• Monitor for dyspnea or new/increased fatigue. If these symptoms develop, assess patient for pulmonary arterial hypertension.
• Monitor patient for signs of depression, suicidal thoughts, or hallucinations (irritability, depression nervousness, anxiety, aggressive behavior, thoughts of hurting self or suicide, hallucinations) during therapy. If depression occurs, notify health care professional immediately.

Lab Test Considerations:

Monitor hemoglobin, WBC, platelets, and blood chemistries including liver function tests prior to and 1, 3, and 6 mo after initiation of therapy. Therapy may be temporarily discontinued if ANC <750/mm³ , if AST or ALT exceeds 10 times the upper limit of normal (ULN), or if serum bilirubin exceeds 5 times ULN. Once the absolute neutrophil count is > 750/mm³  or the hepatic enzymes have returned to normal, therapy can be restarted at 50% of the original dose.

• Thyroid function tests should also be monitored every 6 mo, especially in those patients with a history of thyroid abnormalities.

Implementation

• Do not confuse products. Interferon beta-1a and interferon beta-1b are not interchangeable.
• Consider use of analgesics and/or antipyretics to help ameliorate flu-like symptoms associated with use on treatment days.
• Rotate sites with each injection to minimize risk of injection site reactions (pain, erythema, edema, cellulitis, abscess, necrosis). Avoid areas that are inflamed, edematous, erythematous, ecchymotic, or has signs of infection.
• IM Avonex: Inject into the thigh or upper arm.
• SUBQ Rebif: Administer SUBQ via prefilled, single-use syringe at the same time (preferably the late afternoon or evening) on the same days (Monday, Wednesday, Friday) at least 48 hr apart each wk. Discard unused portions. Store in refrigerator.

Patient/Family Teaching

 Home Care Issues:

Instruct patient in correct technique for injection and care and disposal of equipment. Caution patient not to reuse needles or syringes and provide patient with a puncture-resistant container for disposal.

• Instruct patient to take medication as directed; do not change dose or schedule without consulting health care professional. Patients should receive a medication guide with each product.
• May cause injection site reactions, including injection site necrosis. Periodically assess patient understanding and use of aseptic self-injection techniques, particularly if injection site necrosis has occurred. Discontinuation of therapy following a single site of necrosis is based on the extent of necrosis. For patients who continue therapy after injection site necrosis has occurred, avoid administration into affected area until fully healed. If multiple lesions occur, change injection site or discontinue therapy until healing occurs.
• Inform patient that flu-like symptoms (fever, chills, myalgia, sweating, malaise) may occur during therapy. Acetaminophen may be used for relief of fever and myalgias. Advise patients that starting with a lower dose than 30 mcg and increasing dose over wks reduces incidence and severity of flu-like symptoms.
• Advise patient and family to notify health care professional immediately if signs and symptoms of depression, suicide, hallucinations, liver problems (nausea, yellowing of skin or white part of eye, loss of appetite, bleeding more easily than usual, tiredness, dark colored urine and pale stools, confusion, sleepiness), shortness of breath, difficulty breathing, fatigue, or allergic reactions (itching; swelling of face, eyes, lips, tongue or throat; trouble breathing; anxiousness; feeling faint; rash; hives; sores in mouth, skin blisters and peels) occur.
• Rep:  Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected, or if breastfeeding.

Evaluation/Desired Outcomes

Decrease in the frequency of relapse (neurologic dysfunction) in patients with relapsing-remitting multiple sclerosis.