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Injected vs. Infused Biologics: What’s the Difference?

Posted on February 04, 2022
Medically reviewed by
Ariel D. Teitel, M.D., M.B.A.
Article written by
Joan Grossman

  • Biologic drugs used to treat axial spondyloarthritis (axSpA) must be given by injection — either intravenous (IV) infusion or subcutaneous (under the skin) injection.
  • IV infusions must be given in a medical setting and may take longer to administer, but they can be taken less frequently.
  • Subcutaneous injections may be self-injected at home, but may require more frequent doses.

Biologic drugs currently available for the treatment of axial spondyloarthritis must be taken by subcutaneous injection or IV infusion. If you are considering biologic treatment for axSpA — also referred to as spondylitis or spondyloarthritis — it’s important to understand the differences between injected and IV infused treatments and what to expect from each.

Why Are Biologics Taken by Injection or Infusion?

Biologics are a type of disease-modifying antirheumatic drug (DMARD) made from genetically engineered proteins. These drugs can be effective in the treatment of autoimmune diseases like spondylitis and other types of inflammatory arthritis when nonsteroidal anti-inflammatory drugs (NSAIDs) and other anti-inflammatory treatments have not worked well. Conventional DMARDs like methotrexate are sometimes prescribed along with biologics.

Read more about conventional vs. biologic DMARDs.

Biologic medications are highly complex compounds that consist of large molecules, which are not effectively absorbed in the digestive tract if taken orally. Instead, they must be administered by IV infusion or injection. Biologics contain genetically modified proteins designed to target specific aspects of the immune system that cause chronic inflammation in people with spondylitis.

A number of factors determine which biologic drugs must be infused rather than injected. Some biologics are more sensitive and at higher risk for degradation, while others may be thicker and more viscous. Some biologic treatments also require higher doses that may not be appropriate for injection. These medications require IV infusions for proper dosage, and are administered in a medical setting by a trained clinician.

Classes of Biologics

Each class of biologic drugs targets a particular aspect of the immune system. Each medication approved by the U.S. Food and Drug Administration (FDA) for the treatment of axSpA has specific indications that determine whom it may be recommended for.

Tumor Necrosis Factor-Alpha Inhibitors

Tumor necrosis factor-alpha (TNF-alpha) inhibitors available for subcutaneous injection include:

Another TNF inhibitor, infliximab (Remicade), is also available by IV infusion, depending on the details of the prescription.

Interleukin Inhibitors

Interleukin (IL) inhibitors target specific interleukins, designated by numbers. IL-17 inhibitors include secukinumab (Cosentyx), available as IV infusion or injection, and ixekizumab (Taltz), available as injection. Ustekinumab (Stelara) is an IL-12/23 inhibitor that is administered as an IV infusion and injection.

Read more about biologics and spondylitis.

The Difference Between IV Infusion and Injection

IV infusions and subcutaneous injections are different methods for taking a biologic drug. IV infusions deliver the medication directly into the bloodstream through a needle that is inserted into a vein. Subcutaneously injected biologics are taken with a needle that releases the drug under the skin.

Some people with spondylitis may feel their symptoms improve soon after starting biologic therapy. However, it may take several weeks or months to take full effect. Your doctor can help you understand when you might expect to notice improvement.

IV Infusions: What To Expect

Biologic infusions are usually given at medical facilities. You will have an IV needle inserted into your hand or arm. The medication will be released slowly as a drip from a bag and into a tube that is attached to the needle. An infusion pump is sometimes used to regulate the dosage of the drug. An infusion can take time depending on the drug and the prescribed dosage. Some biologic infusions take only 15 minutes, while others can take several hours.

It is not uncommon for people with spondylitis to be wary of infusions, but many people adjust easily to the procedure, which is relatively painless. Typically, an infusion is experienced as a quick pinprick as the needle is inserted into a vein.

Injections: What To Expect

Subcutaneous injections can be administered quickly with a syringe, either at home or in a clinical setting, similar to other types of shots or vaccines. Subcutaneous injections release medication through a needle into the fatty tissue under the skin.

Many injectable biologics can also be taken by self-injection, which is a safe and convenient way to administer medication at home. Self-injection uses prefilled syringes or auto-injectors — injection pens or e-devices — that come prefilled with the proper dose of the drug.

Self-injection can be done in the comfort of one’s home, which can help reduce visits to the doctor’s office. While a fear of needles is common, many people appreciate the convenience of self-injection and adjust well to the procedure.

Read more about overcoming the fear of self-injection.

Injection Site Reactions

Whether a biologic drug is infused in a clinic or self-injected, it’s common for a person to experience reactions at the injection site as a side effect. Common skin reactions include redness, itching, pain, or swelling, which may be prevented by changing the method of injection.

Be sure to talk to your doctor if you have a reaction at the site of injection. Other side effects may be due to the particular biologic medication. Your doctor will discuss medication side effects with you.

Read more about getting started with biologics.

Advantages and Disadvantages

Depending on the particular medication your doctor recommends, you may have choices as to how to take your biologic therapy. Your health care provider can discuss advantages and disadvantages of injections and infusions.

Scheduling Differences

IV infusions must be given in a clinical setting and require more time than a subcutaneous injection. However, IV infusions are given in larger doses, which may allow you to receive your medication less frequently than by subcutaneous injection.

Scheduling can vary considerably among biologics. Some biologics taken by infusion may be taken monthly or once every eight weeks. Some self-injections might be scheduled every week. Your rheumatologist will discuss scheduling in detail with you to be sure you understand your treatment plan and how to adhere to it.

Discuss Your Options With Your Medical Team

Talk to your rheumatologist and health care team about self-injections and IV infusions if you are considering biologics as a treatment option. Biologic drugs can significantly improve symptoms and quality of life for some people with spondylitis. Understanding the options you may have with infusions or injections of biologics may help improve your experience with these drugs.

Talk With Others Who Understand

On MySpondylitisTeam, the social network for people with spondylitis and their loved ones, more than 85,000 members come together to ask questions, give advice, and share their stories with others who understand life with spondylitis.

Do you have questions about self-injection or IV infusion for biologic treatment? Share your experience in the comments below, or start a conversation by posting on your Activities page.

All updates must be accompanied by text or a picture.
Ariel D. Teitel, M.D., M.B.A. is the clinical associate professor of medicine at the NYU Langone Medical Center in New York. Review provided by VeriMed Healthcare Network. Learn more about him here.
Joan Grossman is a freelance writer, filmmaker, and consultant based in Brooklyn, NY. Learn more about her here.

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