Plegridy (peginterferon beta-1a) is a disease-modifying therapy for relapsing-remitting multiple sclerosis (RRMS). It is given as a subcutaneous (under the skin) injection every two weeks.

Interferon beta helps regulate the immune system and reduce the inflammation that causes MS relapses. Pegylation (attaching polyethylene glycol to the interferon molecule) extends its activity in the body, allowing it to be given less frequently than non-pegylated forms of interferon beta-1a such as Avonex or Rebif.

Plegridy is injected under the skin every 14 days (every 2 weeks). The first two doses use lower starter doses (63 mcg and 94 mcg) to allow your body to adjust before reaching the full maintenance dose of 125 mcg from dose three onwards.

Your neurologist or MS nurse will show you how to inject using the pre-filled pen or syringe. Common injection sites include the abdomen, thigh, or outer upper arm. Rotate sites with each injection.

Inject on the same day of the week every two weeks. Keep a note of your injection dates.

If you miss an injection, administer it as soon as you remember. Then reschedule your next injection 14 days from that date. Never inject two doses within 14 days of each other.

Contact your neurologist or a poison control centre immediately.

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

Side effects are common, particularly during the first months of treatment.

Very common side effects:

• Flu-like symptoms: fever, chills, aching muscles, headache, and fatigue, usually occurring within hours of injection and resolving over 24 to 48 hours. Taking paracetamol before and after injection helps
• Injection site reactions: redness, swelling, pain, bruising, or skin changes at the injection site
  
  

Common side effects:

• Headache
• Muscle aches
• Nausea
• Elevated liver enzymes: liver function tests are checked regularly
  
  

Serious side effects:

• Depression: interferon can cause mood changes and depression. Report any worsening mood or thoughts of self-harm to your doctor immediately
• Severe liver problems: report jaundice (yellow skin or eyes), dark urine, or unusual fatigue
• Injection site necrosis (skin death): rare but serious. Rotate sites carefully and report any skin changes
• Seizures: rare, particularly in patients with a history of seizures

Blood tests for liver function and blood count are done at regular intervals.

• Immunosuppressants or other disease-modifying MS therapies: increased risk of immune suppression when combined
• Medicines metabolised by CYP450 enzymes: interferon can affect the metabolism of some drugs

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

Will the flu-like symptoms get better over time?

Yes. For most people, flu-like symptoms are worst in the first two to three months and gradually lessen as your body adjusts. Taking paracetamol (or ibuprofen if appropriate) 30 to 60 minutes before each injection and again a few hours afterwards can significantly reduce the severity. Injecting in the evening also helps, as you can sleep through the worst of the symptoms. If they remain severe and persistent, talk to your neurologist.

How do I know if Plegridy is working?

The goal of Plegridy is to reduce the frequency and severity of relapses and slow disability progression. It does not cure MS. Your neurologist will assess your MS activity through clinical review and MRI scans. It is important to continue treatment even if you feel well, as the medicine may be preventing relapses that would otherwise occur.

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.