Rebif (interferon beta-1a) is a disease-modifying therapy for relapsing-remitting multiple sclerosis (RRMS). It is given as a subcutaneous (under the skin) injection three times per week.

Interferon beta-1a helps regulate the immune system and reduces the inflammation that drives MS relapses and new lesion formation in the brain and spinal cord. Rebif contains the same interferon as Avonex but is given subcutaneously three times a week (rather than intramuscularly once a week), which provides a different pharmacokinetic profile and requires different monitoring.

Inject Rebif three times weekly (such as Monday, Wednesday, and Friday) at the same time of day. Leave at least 48 hours between each injection.

Treatment starts at a lower dose (8.8 mcg) for the first two weeks, then increases to 22 mcg for weeks three and four, before reaching the maintenance dose of either 22 mcg or 44 mcg three times weekly.

Your neurologist or MS nurse will show you how to inject using the autoinjector (Rebidose) or standard syringe. Suitable sites include the abdomen, thigh, or outer upper arm. Rotate sites with each injection.

Remove from the fridge 30 minutes before injecting.

If you miss a scheduled injection, administer it as soon as you remember, then resume your usual injection schedule. Do not inject two doses on the same day.

Contact your neurologist or a poison control centre.

• Store in a refrigerator between 2°C and 8°C
• Do not freeze
• Keep in the original carton to protect from light
• May be stored at room temperature (up to 25°C) for one single period of up to 30 days
• Keep out of reach of children

Very common side effects:

• Flu-like symptoms: fever, chills, headache, and muscle aches, usually occurring within hours of injection and resolving within 48 hours. These improve over the first two to three months
• Injection site reactions: redness, pain, swelling, or bruising. Rotate sites carefully to minimise this

Common side effects:

• Liver enzyme elevations: regular liver blood tests are required
• Low blood counts: anaemia, low white blood cells, and low platelets
• Depression and mood changes
  

Serious side effects:

• Hepatotoxicity: severe liver damage, including cases of acute liver failure, have been reported rarely. Report jaundice, dark urine, or unusual fatigue
• Severe depression or suicidal thoughts: seek immediate medical help
• Injection site necrosis: rotate sites carefully and seek medical attention for any significant skin breakdown

Blood tests for liver function, thyroid function, and blood count are checked at regular intervals.

• Immunosuppressants or other disease-modifying therapies: avoid combining without specialist guidance
• Medicines metabolised by liver enzymes: interferon can affect the breakdown of some drugs
  

Tell your neurologist and all treating doctors about all medicines you take.

What is the difference between Rebif and Avonex?

Both Rebif and Avonex contain interferon beta-1a, the same active ingredient. The key differences are: Rebif is given subcutaneously (under the skin) three times a week, while Avonex is given intramuscularly (into the muscle) once a week. Rebif comes in two doses (22 mcg and 44 mcg); Avonex is given at 30 mcg. Studies suggest higher-frequency subcutaneous interferon provides slightly better efficacy in some measures, but the twice-weekly injection schedule can be more demanding. Your neurologist will choose the most suitable option for you.

Do the flu-like symptoms ever go away?

Yes, for most people. Flu-like symptoms are most troublesome in the first two to three months and typically reduce significantly after that. Taking paracetamol or ibuprofen before and for a few hours after injection helps considerably. Injecting in the evening so you sleep through the worst of it is also a helpful strategy.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.