Avonex

Avonex,

trademark for an antiviral and immune system regulator (interferon beta-1a) useful for treating multiple sclerosis.

---

interferon beta-1a

Avonex, Rebif

Pharmacologic class: Biological response modifier

Therapeutic class: Antiviral, immunoregulator

Pregnancy risk category C

Action

Binds and competes with specific receptors on cell surface, inducing various interferon-induced gene products. Also inhibits proliferation of T cells.

Availability

Lyophilized powder for injection (beta-1a): 22 mcg (6 million international units; Rebif), 33 mcg (6.6 million international units; Avonex), 44 mcg (12 million international units; Rebif)

Powder for injection (beta-1b): 0.3 mg (9.6 million international units; Betaseron)

Prefilled syringes (beta-1a): 30 mcg/0.5 ml (Avonex)

⊘Indications and dosages

➣ To reduce frequency of exacerbations in relapsing-remitting multiple sclerosis

Adults ages 18 and older: 8.8 mcg Rebif subcutaneously three times weekly, increased over a 4-week period to 44 mcg three times weekly. Or 30 mcg Avonex I.M. once a week. Or 8 million international units (0.25 mg) Betaseron subcutaneously every other day.

Contraindications

• Hypersensitivity to drug, its components, or albumin

Precautions

Use cautiously in:
• cardiac disease, seizure disorders, mental disorders, depression, suicidal tendencies
• women of childbearing age
• pregnant or breastfeeding patients
• children ages 18 and younger.

Administration

• Reconstitute Avonex (I.M. injection) and Rebif (subcutaneous injection) using diluent provided, according to instructions provided.
• Reconstitute Betaseron (subcutaneous injection) using 1.2 ml of diluent supplied by manufacturer, to yield a concentration of 0.25 mg/ml. Swirl gently to mix; don't shake. Use reconstituted drug within 3 hours; discard unused portion.

Route	Onset	Peak	Duration
I.M.	Unknown	Unknown	Unknown
Subcut.	Unknown	1-8 hr	Unknown

Adverse reactions

CNS: dizziness, confusion, rigors, paresthesia, lethargy, depression, difficulty thinking or concentrating, insomnia, anxiety, fatigue, amnesia, nervousness, drowsiness, asthenia, malaise, suicidal ideation

CV: chest pain, hypertension, palpitations, arrhythmias

EENT: visual disturbances, stye, hearing disorders, nasal congestion, sinusitis, rhinitis, pharyngitis

GI: nausea, vomiting, diarrhea, constipation, abdominal pain, dyspepsia, flatulence, eructation, stomatitis, dry mouth, intestinal obstruction

GU: gynecomastia, breast pain, early or delayed menses, menstrual bleeding or spotting, shortened duration of menstrual flow, menorrhagia

Hematologic: anemia, neutropenia , leukopenia, thrombocytopenia

Metabolic: hypocalcemia

Musculoskeletal: joint pain, back pain, myalgia, myasthenia

Respiratory: cough, dyspnea

Skin: rash, dry skin, pruritus, flushing, alopecia, dermatitis, diaphoresis

Other: gingivitis, flulike symptoms, weight loss, edema, candidiasis, lymphadenopathy, inflammation, pain

Interactions

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine, glucose, lactate dehydrogenase, neutralizing antibodies, phosphorus, uric acid: increased values

Hemoglobin, neutrophils, white blood cells: decreased values

Patient monitoring

☞ Before therapy and monthly during therapy, assess CBC with white cell differential, glucose and electrolyte levels, and liver and kidney function tests.
• Assess fluid intake and output. Keep patient well hydrated.
• Watch for GI upset. Provide small, frequent meals to minimize nausea and vomiting.
☞ Monitor for mental status changes, depression, and suicidal ideation.
• Evaluate for bleeding and bruising.
• Institute infection-control measures. Monitor for infection symptoms.

Patient teaching

• Teach patient or caregiver how to administer drug subcutaneously or I.M., rotate injection sites, and track dosing schedule and injection sites on calendar.
• Advise patient to avoid sources of potential infection, such as crowds and people with known infections.
• Tell patient to eat small, frequent meals to combat nausea, vomiting, and appetite loss.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, alertness, and vision.
☞ Tell patient to contact prescriber immediately if depression or suicidal ideation occurs.
• Inform female patient that drug is linked to fetal abnormalities. Advise her not to get pregnant during therapy, and to use barrier contraception. Tell her to consult prescriber before breastfeeding.
☞ Instruct patient to immediately report signs of symptoms of infection (such as fever, chills, sore throat, achiness), unusual bleeding or bruising, mental status changes, dizziness, palpitations, or chest pain.
• Tell patient he'll need regular follow-up examinations and blood tests to monitor drug effects.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the tests mentioned above.