Interferon Beta-1a

Pronunciation: (IN-ter-FEER-on BAY-ta)
Class: Immunomodulator

Trade Names

Avonex
- Powder for injection, lyophilized 33 mcg (6.6 million units)
- Prefilled syringe 30 mcg per 0.5 mL

Rebif
- Prefilled syringe 8.8 mcg per 0.2 mL
- Prefilled syringe 22 mcg per 0.5 mL
- Prefilled syringe 44 mcg per 0.5 mL

Avonex PS (Canada)

Pharmacology

Has antiviral, antiproliferative, and immunoregulatory activities. Binds to specific cell membrane receptors that induce the expression of a number of gene products that mediate the biological actions of interferon beta-1a.

Pharmacokinetics

Absorption

T _max is 3 to 15 h ( Avonex ). C _max is 5.1 units/mL; AUC _{0 to 96} is 294 units•h/mL; T _max is 16 h ( Rebif ).

Elimination

The t _½ is 10 h ( Avonex ). Total Cl is approximately 33 to 55 L/h; t _½ is 69 h ( Rebif ).

Indications and Usage

Treatment of relapsing forms of multiple sclerosis to slow accumulation of physical disability and decrease the frequency of clinical exacerbations.

Contraindications

Hypersensitivity to natural or recombinant interferon beta, human albumin, or any other component of the formulation.

Dosage and Administration

Adults Avonex

IM 30 mcg once weekly.

Rebif

Subcutaneous Titrate dose to 22 or 44 mcg 3 times/wk.

Titration schedule for 22 mcg

Wk 1 and 2, administer 4.4 mcg 3 times/wk. Wk 3 and 4, administer 11 mcg 3 times/wk. Wk 5 and on, administer 22 mcg 3 times/wk.

Titration schedule for 44 mcg

Wk 1 and 2, administer 8.8 mcg 3 times/wk. Wk 3 and 4, administer 22 mcg 3 times/wk. Wk 5 and on, administer 44 mcg 3 times/wk.

General Advice

Avonex
Administer via IM route only. Not for intradermal, subcutaneous, or IV administration.
Rotate injection sites (thighs and upper arms). Use a different area from where last injection was administered. Do not inject into areas where the skin is infected, tender, bruised, red, or hard.
Allow prefilled syringe to warm to room temperature before administering. Do not warm using external heat source (eg, hot water).
Reconstitute powder for injection using supplied diluent only. Swirl vial gently to dissolve. Do not shake vial.
Reconstituted solution should be clear to slightly yellow.
Do not administer if particulate matter, cloudiness, or discoloration is noted.
Withdraw prescribed dose into syringe for injection and administer immediately or within 6 h if stored in refrigerator (36° to 46°F) after reconstitution.
Vials contain no preservative. Discard any unused portion. Do not combine unused portions.

Rebif
Administer via subcutaneous route only. Not for intradermal, IM, or IV administration.
Rotate injection sites (buttocks, thighs, abdomen, back of arms). Use a different area from where last injection was administered. Do not inject into areas where the skin is tender, bruised, red, or hard.
Do not mix with other drug solutions.

Storage/Stability

Avonex

Store prefilled syringes and unopened vials in refrigerator (36° to 46°F). Do not freeze. If a refrigerator is not available, unopened vials, but not prefilled syringes, may be stored at temperatures at or less than 77°F for up to 30 days, away from heat and light. Once warmed to room temperature, prefilled syringe must be used within 12 h.

Rebif

Store prefilled syringes in refrigerator (36° to 46°F). Do not freeze. If a refrigerator is not available, prefilled syringes may be stored at temperatures at or less than 77°F for up to 30 days, away from heat and light.

Drug Interactions

Myelosuppressive agents

Because of potential to cause neutropenia and lymphopenia, monitor patients during concomitant therapy.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Upper respiratory tract infection (14%); bronchitis (8%).

Miscellaneous

Avonex

Flu-like symptoms (49%); asthenia (24%); pain (23%); fever (20%); chills (19%); infection (7%); chest pain, neutralizing antibodies (5%); anaphylaxis (postmarketing).

Rebif

Flu-like symptoms (59%); neutralizing antibodies (31%); fever (28%); rigors (13%); chest pain (8%); malaise (5%); anaphylaxis.

Precautions

Monitor

Ensure that Hgb, CBC with differential, platelet count, and blood chemistries, including LFTs, are performed before initiating therapy, at 1, 3, and 6 mo after starting therapy, and then periodically thereafter. Ensure that thyroid function tests are performed before starting therapy and every 6 mo during therapy in patients with thyroid dysfunction.

Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy in children younger than 18 yr of age not established.

Elderly

Use with caution because of greater frequency of decreased hepatic, renal, or cardiac function, and concomitant diseases or other drug therapy ( Rebif ).

Albumin

Product contains albumin, a derivative of human blood; therefore, there is a remote risk for transmission of viral diseases.

Anaphylaxis

Anaphylaxis has been reported as a rare complication.

Autoimmune disorders

Autoimmune disorders of multiple target organs have been reported, including idiopathic thrombocytopenia, hyperthyroidism, and hypothyroidism, and rare cases of autoimmune hepatitis. Monitor for signs of these disorders and implement appropriate treatment when observed ( Avonex ).

Cardiomyopathy and CHF

Patients with cardiac disease, such as angina, CHF, or arrhythmia, should be closely monitored for worsening of clinical condition during initiation and continuation of treatment ( Avonex ).

Decreased peripheral blood counts

Decreased peripheral blood counts in all cell lines, including rare pancytopenia and thrombocytopenia, may occur ( Avonex ).

Hepatic injury

Severe liver function injury, leading to hepatic failure requiring liver transplantation, may occur; asymptomatic elevation of hepatic transaminases has occurred.

Seizures

Use caution when administering to patients with preexisting seizure disorder.

Suicide/Depression

Suicidal ideation occurred in clinical trials. Report depression and suicidal ideation immediately.

Patient Information

Advise patient, family, or caregiver that medication is not a cure for multiple sclerosis, but it may decrease the number of flare-ups and slow the development of some of the physical disabilities caused by multiple sclerosis.
Advise patient or caregiver to review the Medication Guide before using and with each refill.
If patient or caregiver will be administering at home, ensure that he/she understands how to store, prepare, and administer the dose, and how to dispose of used equipment and supplies. If possible, first injection should be performed under supervision of a qualified health professional.
Advise patient not to change the dose or stop taking unless advised by health care provider.
Advise patient that flu-like symptoms are common and that OTC fever and pain reducers (eg, acetaminophen, ibuprofen) can be used to relieve fever and muscle aches.
Advise patient to notify health care provider immediately if any of the following occur: drainage of fluid, injection-site reaction with break in skin and blue-black discoloration, severely depressed mood, suicidal ideation, swelling.
Advise patient to contact health care provider if experiencing bothersome adverse reactions or any unusual problems.
Advise women of childbearing potential to use effective contraception during treatment because of the abortifacient potential of these medications.

Avonex
Advise patient that if a dose is missed to take it as soon as possible and then continue regular schedule the following week.
Instruct patient to rotate injection sites as described in the Medication Guide to minimize likelihood of severe injection-site reactions.
Caution patient or caregiver that the prefilled syringe cap contains dry natural rubber that should not be handled by individuals sensitive to latex.

Rebif
Advise patient that if a dose is missed to take it as soon as possible and to schedule next dose approximately 48 h later.
Instruct patient to rotate injection sites as described in the Medication Guide to minimize likelihood of severe injection-site reactions or tissue necrosis.

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