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)

Lyophilized powder for injection (beta-1b): 0.3 mg in glass, single-use, 3-ml vial

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. Or initially, 0.0625 mg (0.25 ml) (Extavia) subcutaneously every other day, increased over 6 weeks to 0.25 mg (1 ml) 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.

• Reconstitute Extavia (subcutaneous injection) by attaching prefilled, single-use syringe containing 1.2 ml of diluent supplied by manufacturer to vial using vial adapter. Slowly inject 1.2 ml of diluent into vial 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.

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

See 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.

See 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.

See 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.

See Instruct patient to immediately report signs or 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.