Peginterferon Beta-1a Injection
Peginterferon beta-1a is an interferon beta used to treat relapsing forms of multiple sclerosis in adults.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
📖 Peginterferon Beta-1a Injection: Patient Information Guide
A plain-language walkthrough of Peginterferon Beta-1a Injection — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Peginterferon beta-1a is used to treat relapsing forms of multiple sclerosis (MS) in adults. All current approvals are for Plegridy, available as a subcutaneous or intramuscular injection.
- Clinically isolated syndrome (CIS): A first neurological episode suggestive of MS — Plegridy is approved for treatment at this early stage
- Relapsing-remitting MS (RRMS): The most common form of MS, marked by episodes of new or worsening symptoms followed by partial or full recovery
- Active secondary progressive MS (SPMS): A later stage of MS where disability gradually increases, but ongoing relapses are still occurring
⚙️How it works▾
Plegridy belongs to the interferon beta family — proteins that play a role in regulating the immune system. The exact way it helps in MS is not fully known, but interferon beta products are thought to reduce the immune system's abnormal attack on the myelin sheath (the protective coating around nerve fibers) that causes MS symptoms and relapses. The "peg" in peginterferon means the molecule has been modified with polyethylene glycol (PEG), which allows it to stay active in the body longer than standard interferon beta-1a, enabling a less frequent dosing schedule.
💊How it's taken▾
Plegridy is injected every 14 days (once every two weeks). To reduce flu-like symptoms that are common when starting treatment, the dose is gradually increased over the first month, beginning at a lower amount and stepping up to the full maintenance dose by day 29. It can be given as a subcutaneous injection (under the skin) or intramuscular injection (into the muscle), but switching between routes has not been formally studied.
- Subcutaneous injections use a prefilled pen or prefilled syringe; intramuscular injections use a prefilled syringe with a separate needle
- Rotate injection sites every time to reduce skin reactions
- Allow the pen or syringe to warm at room temperature for about 30 minutes before each injection
- Taking a pain reliever or fever reducer on injection days may help ease flu-like symptoms — ask your prescriber
🤒Side effects — in detail▾
The most common side effects with Plegridy subcutaneous injection include:
- Injection site redness, pain, itching, or swelling
- Flu-like illness (fever, chills, muscle aches)
- Fever
- Headache
- Muscle pain (myalgia)
- Fatigue or weakness
- Joint pain (arthralgia)
- Nausea or vomiting
- Elevated liver enzymes (detected on blood tests)
Serious reactions — including severe liver injury, depression or suicidal thoughts, severe allergic reactions (anaphylaxis), very low blood cell counts, a rare clotting disorder (thrombotic microangiopathy), and high blood pressure in the lung arteries (pulmonary arterial hypertension) — require prompt medical attention. Contact your doctor or seek emergency care right away if any of these occur.
⚠️Warnings & precautions▾
- Liver injury: Plegridy can cause serious liver damage, including hepatitis and rare liver failure. Regular liver function tests are needed during treatment.
- Depression and suicidal thoughts: These occur more often in people using interferon beta. Report any mood changes or thoughts of self-harm to your doctor immediately.
- Severe allergic reactions (anaphylaxis): Rare but serious; stop Plegridy and get emergency help if you develop swelling, hives, or difficulty breathing.
- Injection site reactions: Redness and pain are common. Rare but serious skin tissue damage (necrosis) can occur. Rotate sites every injection and keep the area clean.
- Low blood cell counts: Plegridy can lower white blood cells, platelets, and other blood cells, increasing infection or bleeding risk. Blood count monitoring is recommended.
- Thrombotic microangiopathy (TMA): A rare but serious blood-clotting disorder has been reported; stop Plegridy if this is diagnosed.
- Pulmonary arterial hypertension (PAH): High blood pressure in the lung arteries has been reported, sometimes years after starting treatment. Tell your doctor about unexplained shortness of breath or new fatigue.
- Heart problems: Those with pre-existing heart disease should be monitored for worsening symptoms during treatment.
- Autoimmune disorders: New autoimmune conditions — including thyroid problems or low platelet counts — can develop; discuss any new symptoms with your doctor.
- Seizures: Use with caution if you have a history of seizure disorder.
🔀What it interacts with▾
The Plegridy label does not list specific named drug interactions, but there are important considerations to discuss with your healthcare provider:
- Immunosuppressant medications: Combining treatments that suppress the immune system may increase infection risk — always tell your doctor about all medications you take
- Liver-affecting medications: Because Plegridy can raise liver enzymes, other drugs known to stress the liver warrant careful monitoring
- Latex allergy: The rubber cover on the Plegridy prefilled syringe for intramuscular use contains natural rubber latex — those with latex sensitivity should alert their healthcare provider before use
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Allergy to interferon beta or peginterferon: Plegridy is contraindicated if you have ever had a serious allergic reaction to these substances or any component of the product
- Liver disease: Tell your doctor about any history of liver problems — monitoring will be needed
- Depression or mental health history: Plegridy may worsen depression; discuss your mental health history with your prescriber
- Heart disease: Those with significant cardiac disease, including congestive heart failure, need monitoring during treatment
- Severe kidney disease: The drug can build up more in the body with severe renal impairment — closer monitoring for side effects is recommended
- Seizure disorder: Use with caution; tell your doctor if you have a history of seizures
- Pregnancy: Animal studies suggest interferon beta may cause pregnancy loss. Human data have not shown a clear increase in major birth defects, but the evidence is mixed. Discuss risks and benefits with your doctor before or during pregnancy
- Breastfeeding: Small amounts of interferon beta-1a have been detected in breast milk. Discuss risks and benefits with your doctor
- Children: Safety and effectiveness in pediatric patients have not been established
- Older adults: Clinical studies did not include enough patients 65 and older to draw firm conclusions; use with the same cautions as in younger adults
- Latex sensitivity: The Plegridy intramuscular prefilled syringe contains natural rubber latex — inform your healthcare provider if you are latex-sensitive
📡Pharmacodynamics — effects in the body▾
No specific biochemical or physical effect has been identified that directly explains how Plegridy produces its clinical benefit in multiple sclerosis. The relationship between any measurable body response and the drug's effect on MS has not been established.
🔬Pharmacokinetics — how your body processes it▾
After a subcutaneous injection of Plegridy, the drug reaches its peak blood level within about 1 to 1.5 days. The half-life — the time for the body to clear half the drug — is approximately 78 hours (about 3 days) in MS patients, which is why it only needs to be given every two weeks without building up in the blood over time. The drug is cleared mainly through the kidneys, and people with severe kidney disease may have higher drug levels in their body and need closer monitoring. Plegridy is not extensively broken down by the liver. Body weight, sex, and age do not require dose adjustments.
📦How to store it▾
Store PLEGRIDY prefilled pens and prefilled syringes in a refrigerator between 2°C to 8°C (36°F to 46°F) in the closed original carton to protect from light until ready for injection. Do not freeze.
📄 Written from Peginterferon Beta-1a Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Peginterferon Beta-1a Injection
38 supplements and herbal products have documented interactions with Peginterferon Beta-1a Injection in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 3
- Moderate · 35
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Peginterferon Beta-1a Injection — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is Plegridy doing for my MS? ▾
Why do I have to start on a lower dose and work my way up? ▾
What side effects should I just watch and wait on, versus ones that mean I should call someone right away? ▾
Is it safe to use Plegridy if I'm pregnant or trying to get pregnant? ▾
Do I need any blood tests while I'm on Plegridy? ▾
Does it matter whether I inject it under the skin or into the muscle — are they the same? ▾
Is Peginterferon Beta-1a Injection available over the counter? ▾
When was Peginterferon Beta-1a Injection first available? ▾
💬 Answers drafted from Peginterferon Beta-1a Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Peginterferon Beta-1a Injection comes
Peginterferon Beta-1a Injection is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Injection
How this form is used
- Plegridy subcutaneous injection is used to treat relapsing forms of MS in adults, including clinically isolated syndrome, relapsing-remitting MS, and active secondary progressive MS
- Plegridy intramuscular injection is also approved for relapsing forms of MS in adults
- Plegridy subcutaneous injection is given every 14 days using a prefilled pen or prefilled syringe; rotate sites among the abdomen, back of the upper arm, or thigh
- Plegridy intramuscular injection is given every 14 days using a prefilled syringe; rotate sites between the left and right thighs
- Plegridy should be removed from the refrigerator and allowed to warm to room temperature (about 30 minutes) before injecting — do not use hot water or other heat sources to warm it
- Plegridy dose is started low and increased gradually over the first four weeks to help reduce flu-like symptoms; a healthcare professional should train you on proper self-injection technique
📊 Peginterferon Beta-1a Injection across the U.S. market
How Peginterferon Beta-1a Injection appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Kit (4) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
📈 How widely Peginterferon Beta-1a Injection is used
A general measure of how commonly Peginterferon Beta-1a Injection is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Peginterferon Beta-1a Injection is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Peginterferon Beta-1a Injection prescribed? Of the 1,597 medications we measure, Peginterferon Beta-1a Injection ranks #1,467 by Medicaid prescriptions — more than 8% of them.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Peginterferon Beta-1a Injection, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 5 listed Peginterferon Beta-1a Injection NDCs with Medicaid activity.
🔍 Compare Peginterferon Beta-1a Injection products
A representative set of FDA-listed product records for Peginterferon Beta-1a Injection — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Injection | ||||
| 125 mcg/0.5 mL | Intramuscular | Biogen Inc. × 4 listings | BLA | View NDC → |
| 125 mcg/0.5 mL | Subcutaneous | Biogen Inc. × 8 listings | BLA | View NDC → |
| 💊Kits | ||||
| — | Subcutaneous | Biogen Inc. × 4 listings | BLA | View NDC → |
Showing 16 of 16 products — FDA National Drug Code Directory. See every product, package size and price: browse all 16 Peginterferon Beta-1a Injection NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Peginterferon Beta-1a Injection — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Peginterferon Beta-1a Injection in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Peginterferon Beta-1a Injection went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 1546168 2 dose forms · 6 strengths
-
Dose form (SCDF) Auto-Injector RxCUI 1649590In current FDA listingsClinical drug / strength (SCD) 0.5 ML peginterferon beta-1a 0.126 MG/MLRxCUI 16496000.5 ML peginterferon beta-1a 0.188 MG/MLRxCUI 16496010.5 ML peginterferon beta-1a 0.25 MG/MLRxCUI 1649591 -
Dose form (SCDF) Prefilled Syringe RxCUI 1546171No current FDA listingClinical drug / strength (SCD) 0.5 ML peginterferon beta-1a 0.126 MG/MLRxCUI 15461810.5 ML peginterferon beta-1a 0.188 MG/MLRxCUI 15461720.5 ML peginterferon beta-1a 0.25 MG/MLRxCUI 1546187
Look up RxCUI 1546168 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Peginterferon Beta-1a Injection is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Peginterferon Beta-1a Injection belongs to the Interferon beta class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Biogen Inc. is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.