Peginterferon Beta-1a (Injection)

Peginterferon beta-1a injection is a medication that is used in the treatment of the relapsing/remitting form of multiple sclerosis (MS).


In the US, peginterferon beta-1a injection is better known by the following brand names:

  • Plegridy Starter Pack
  • Plegridy Pen Starter Pack
  • Plegridy Pen
  • Plegridy

Peginterferon beta-1a is a prescription only medication that comes in solution form for self-administration.

Peginterferon beta-1a injection is the preferred medicine that is used to treat the relapsing/remitting form of multiple sclerosis (MS). Peginterferon beta-1a belongs to a family of medicines called disease-modifying drugs. These medications are synthetic versions of a naturally occurring substance that the body uses to fight infection.

Although peginterferon beta-1a injection will not cure your MS, it may be helpful in slowing down the progression of the disease and reducing the frequency and severity of relapses suffered by the patient.

Conditions treated

  • Relapsing/remitting multiple sclerosis

Type of medicine

  • Disease modifier
  • Solution for injection

Side effects

Together with the effects it is intended to have, peginterferon beta-1a can cause some unwanted side effects. Not every patient using this drug will notice any side effects, but if you do, you may need to seek further medical attention.

If you notice any of the following effects, you should check with your treating specialist or GP:

  • Yellow eyes or skin
  • Vomiting
  • Unusual weakness or tiredness
  • Sleeping problems
  • Tightness of the chest
  • Excessive thirst
  • Sweating
  • Abdominal and stomach pain
  • Skin rash
  • Shivering
  • Runny nose
  • Reddening of the skin
  • Swelling or puffiness around the eyes, eyelids, face, tongue, or lips
  • Clammy, pale skin
  • Muscle cramping
  • Muscular aches and pains
  • Light-colored stools
  • Large, swellings on the face, lips, eyelids, tongue, hands, throat, feet, legs, or genitals
  • Joint pains
  • Itchy skin
  • Welts or hives
  • Feeling generally weak or tired
  • Feeling ill or in general discomfort
  • Fever
  • Rapid, weak heartbeat
  • Rapid, shallow breathing
  • Extremely high body temperature or fever
  • Dizziness
  • Difficulty swallowing
  • Diarrhea
  • Poor appetite
  • Dark urine
  • Cough or sore throat
  • Chills
  • Black/blue/green skin discoloration

When you first begin using peginterferon beta-1a, you may notice a few minor side effects. These effects will usually resolve by themselves as your body gets used to the new medicine. Your GP or MS nurse may also be able to suggest ways in which you can manage these effects. However, if the following listed effects do not settle down within a week or so or are proving particularly annoying, you should check with your doctor:

  • Peeling of skin, pain, or redness at the injection site
  • Muscular aches and pains
  • Muscle stiffness
  • Lack or loss of strength
  • Itching, redness, rash, soreness, warmth, or swelling at the site of the injection
  • Flu-like symptoms
  • Difficulty with moving

The side effects mentioned in this guide may not be the only ones experienced by patients using peginterferon beta-1a. If you experience any other odd effects, you should speak with your MS nurse or GP right away.


Administration guidelines

Initially, you will be given peginterferon beta-1a injection by a trained medical professional. You will also be shown how to prepare and administer this drug yourself. The drug is given as in injection into the muscle or under the skin, usually in your thigh, buttock, back of your upper arm, or abdomen.

You must use peginterferon beta-1a precisely as you are shown by your treating physician. Do not adjust the dose, change the dosage schedule, or stop taking the drug without speaking to your GP or MS nurse first. Your dose rate has been carefully calculated in accordance with your condition and medical history. If you use too much, you risk severe side effects. If you do not use enough, the drug will not be effective.

Your treating physician or nurse will show you where on your body you should inject the dose of medication. It is important that you use a different injection site each time. Make a note of each site so that you remember to rotate them. This will ensure that your skin does not become damaged, bruised, and sore. Always check the injection site after a couple of hours for tenderness, swelling, or redness.

Before administering your injection of peginterferon beta-1a, use the sterile wipes that will be provided with your medicine to clean and disinfect each injection site. Be careful not to touch the end of the syringe or pen against anything, in order to avoid transmitting bacteria into your skin where it could cause an infection.

Avoid injecting into any site where you have bruised, irritated, scarred, or infected skin.

You will be given a mediation guide with your prescription of peginterferon beta-1a. This guide will contain usage instructions, which you should read carefully on how to prepare your injections, how to use your pen or disposable syringes, and how to store the medication.

Dosage guidelines

The dose of peginterferon beta-1a is usually slightly different for different patients. Be sure to keep to the dosage instructions you have been given by your treating physician or those on the product label. The information that follows is based on the average recommended dose. If your dose is at variance with this, do not change it unless you are told to by your treating specialist.

Your dose will depend on the potency of the preparation you are prescribed. The amount of injections you have each day, the time left between each one, and the total duration of your course of treatment with peginterferon beta-1a will be dependent on your medical condition and on how your body responds to the treatment.

Treatment of relapsing/remitting MS:

  • Adults: Use 63 mcg on the first day. This dose will be increased to 94 mcg after two weeks, and then again to 125 mcg two weeks later. Thereafter, use 125 mcg fortnightly.
  • Children: The use and dosage of peginterferon beta-1a will be calculated by your child's treating specialist.

In order for this medicine to be effective, it must be taken on a pre-determined schedule. If you are unable to administer a dose for any reason, check with your GP or MS nurse. Do not use twice the dose.


Drug interactions

There are some drugs that should never be used together, as doing so could cause an interaction. However, in some cases, your treating specialist may decide that using two drugs together is the best treatment strategy in your case. In this case, your medical professional may change the dose of one of your drugs or suggest other precautions that can be taken to mitigate any interaction that may take place. Tell your treating specialist if you are already using any other prescription or over the counter drugs, including herbal remedies or vitamin supplements.

Other interactions

Some medication interacts adversely with certain foods or with tobacco or alcohol. Before you begin taking peginterferon beta-1a injection, make sure that you discuss this aspect of your treatment with your treating physician.

Medical interactions

Some pre-existing medical conditions or a history of them can affect the use of peginterferon beta-1a. Be sure to discuss your medical history in full with your treating specialist, especially if you have ever had any of the following conditions:

Peginterferon beta-1a should be used with caution in patients with the following conditions, as this drug can make these illnesses worse:

Patients who have any form of infection may find that peginterferon beta-1a decreases the body's ability to tackle infections.

Peginterferon beta-1a should be used with caution in patients who have severe kidney disease. The effects of the medication may be increased due to the slow removal of the drug from the body.


When you decide to use peginterferon beta-1a, it is important that you consider the risks of doing so against the benefits it will bring. You should make this decision following discussion with your MS specialist. When deciding whether to use peginterferon beta-1a, you should bear in mind the following points:


Be sure to mention to your treating specialist if you are allergic to peginterferon beta-1a or to any other medication, including both prescription and over the counter products. Tell your doctor if you know that you have allergies to particular food groups, food colors, preservatives, or animal derivatives.


There have been no specific studies into the use of peginterferon beta-1a in children. If you have any concerns in this regard, discuss your child's treatment with their MS specialist.


There have been no specific studies into the use of peginterferon beta-1a in elderly patients. If you have any concerns in this regard, you should discuss your treatment with your MS specialist.

Pregnancy and breastfeeding

According to FDA pregnancy category 'C', idursulfase can present a potential risk to the unborn baby. Pregnant women should therefore tell their medical professional of their condition before they begin using peginterferon beta-1a. If you are intending to become pregnant while treatment is in progress, you must tell your MS specialist.

Although it is not known whether this drug can be ingested by a nursing infant through the mother's breast milk, you should tell your medical professional if you are currently breastfeeding. You may wish to ask your doctor or midwife for guidance on alternative feeding solutions for your infant while you are using idursulfase.

Medical complications

You must attend your MS specialist for regular checks throughout your treatment with peginterferon beta-1a. You will need blood tests and possibly eye tests to make sure that the new drug is working properly to control your symptoms and to address any side effects that it may be causing.

If you notice pain or tenderness in your stomach, dark urine, poor appetite, jaundice, vomiting, or pale stools, you should check with your GP right away, as these could indicate a serious liver problem.

Peginterferon beta-1a can sometimes make some patients feel irritable, anxious, or show other behavior that is not normal for them. Some people also experience suicidal tendencies or thoughts, or become very depressed. If you notice any of these effects, tell your GP immediately.

Some patients can experience anaphylaxis when treated with peginterferon beta-1a. Anaphylaxis is extremely serious and always necessitates emergency treatment. If you notice any of the following symptoms right after using peginterferon beta-1a, call 911:

  • Rash
  • Itchy skin
  • Breathing problems
  • Trouble swallowing
  • Swelling of the mouth, face, hands, or throat

Peginterferon beta-1a injection can cause pain, swelling, or reddening at the administration site. In some cases, a skin necrosis has occurred. If you notice any indentations or depressions in the skin, accompanied by skin discoloration, peeling or pain, check with your GP.

Peginterferon beta-1a usually causes patients to suffer from flu-like symptoms when they first begin using it. To manage these effects, use the injection at bedtime and take ibuprofen and paracetamol in equal amounts. This means that you should sleep through the effects and wake feeling fine in the morning. Once your body gets used to the drug, these effects usually self-resolve.

Some patients may experience heart or fluid retention problems while using peginterferon beta-1a. If you notice any of the following listed symptoms, you should check with your GP right away:

  • Chest pain
  • Shortness of breath
  • Feeling extremely tired or weak
  • Irregular heartbeat
  • Irregular breathing
  • Swelling of the ankles, hands, feet, or wrists

Peginterferon beta-1a can cause a lowering of the amount of white blood cells circulating in your body. This can increase your chances of contracting an infection. Your platelet count may also be lowered, leading to bleeding or poor blood clotting. To manage these possible effects, you can take the following precautions:

1. Try to avoid contact with people who have infections such as coughs and colds.

2. Tell your GP if you notice any unusual bruising or if you have blood in your urine or stools.

3. Take extra care when using your toothbrush, flossing your teeth, and using a toothpick. Ask your dentist or GP for advice on other ways of cleaning your teeth, and alert your dentist to the fact that you are using peginterferon beta-1a before having any dental work carried out.

4. Avoid touching the inside of your nose or your eyes without having washed your hands immediately beforehand.

5. Be very careful when using sharp objects, including fingernail clippers or razors, or when preparing food using a knife.

6. Do not take part in any sports or other activities that could result in injury or bruising.


Keep your prescription of peginterferon beta-1a in your refrigerator but do not freeze it. If you cannot keep your medicine refrigerated, it can be kept for up to a month at room temperature, providing it is not exposed to direct sunlight or heat sources.

If desired, you may warm the product to room temperature before use. However, you should not actively heat the drug in a microwave or oven.

Do not use any peginterferon beta-1a that has become out-of-date or that you no longer need. Ask your pharmacist or GP how to dispose of the drug. Be sure to place used syringes and needles in a special sharps box.

Keep the drug well away from pets and children.


Peginterferon beta-1a injection is used to treat the relapsing/remitting form of multiple sclerosis (MS). The medicine is a disease-modifying drug.

It should be noted that although peginterferon beta-1a injection can be very effective in slowing down the progression of certain forms of MS, it will not cure the disease.

Although most other medications can be used safely with this medicine, there are a number of side effects that patients should be aware of. For this reason you should discuss your full medical history with your MS specialist before you start using peginterferon beta-1a injection. You must also attend your specialist for regular check-ups and blood tests throughout the course of your treatment to make sure that the drug is working properly and to discuss any unwanted side effects that it may be causing.