Infusion vs. injection: Breaking down the basics of these two specialty therapies

By Sofia Shrestha

Senior Director of Clinical Strategy at Leap

In 1995, there were about 30 specialty drugs on the market. Today, there are nearly 1,000, and roughly 75% of the 7,000 drugs moving through the FDA pipeline are specialty drugs.

These medicines treat some of the most complex conditions in healthcare, including multiple sclerosis, Crohn's disease, rheumatoid arthritis, immune deficiencies, and cancer. They also can improve outcomes for patients with certain conditions.

As specialty drugs have evolved, so too have the ways patients receive them. A therapy that once meant hours driving and more hours in an infusion chair at a hospital outpatient department (HOPD) may now be delivered in the home as an injection that takes a few minutes. Several drugs that were IV-only a few years ago now have a faster subcutaneous option. 

Let’s examine what infusion therapies are versus injection therapies. 

What is infusion therapy?

Infusion therapy is a way to deliver medication directly into the body over a set period of time, most often through a vein. A nurse places an IV line, connects the medication, and controls how quickly it flows. 

Most infusions run through a peripheral IV (a short, thin tube placed in a vein in the hand or arm). Patients on longer or more frequent treatment may have a PICC (a thin catheter inserted in the arm that reaches a large vein near the heart) or a port (a small device implanted under the skin that connects to a central vein). Ports are especially common among people receiving cancer treatment.

Infusion is the standard route for many specialty therapies, including: 

• Remicade for Crohn's disease and rheumatoid arthritis.
• Ocrevus for multiple sclerosis.
• Keytruda for a range of cancers.
• Immunoglobulin (IVIG) for primary immunodeficiency. 

Treatment time varies widely. An Ocrevus infusion every six months typically runs a few hours, while IVIG patients often sit through four- to five-hour infusions on two back-to-back days, repeated every three to four weeks.

What is injection therapy?

Injection therapy delivers medication through a needle over seconds or minutes rather than a slow drip. Specialty injections can be subcutaneous (into the fatty tissue just under the skin, often in the abdomen or thigh) or intramuscular (into a muscle).

The tissue under the skin can only absorb a small amount of liquid at once, which previously kept many large-dose biologics IV-only. Newer formulations pair the drug with hyaluronidase, an enzyme that temporarily loosens that tissue so a full dose can be absorbed quickly. That's what allows Darzalex Faspro, a treatment for multiple myeloma, to be given in roughly three to five minutes.

Specialty injections typically fall into two distinct groups:

• Provider-administered injections given by a nurse or other healthcare professional. Darzalex Faspro and Ocrevus Zunovo (a subcutaneous version of Ocrevus) fall into this group, and they're billed on the medical benefit, the same way an infusion is.
• Self-injected therapies designed for patients to give themselves. Kesimpta, a multiple sclerosis therapy, comes in an autoinjector pen patients use at home, and therapies like it are typically covered under the pharmacy benefit like other prescriptions.

What are the benefits to infusions and injections?

Both infusion and injection therapies can improve absorption rates of drugs by bypassing the GI tract and delivering medications more directly into the bloodstream or tissues. For this reason and others, patients can experience improved outcomes, particularly those who are “acutely ill, recovering from surgery, or suffering from chronic malabsorption syndromes,” according to one study.

Many specialty drugs, including Keytruda, Ocrevus, and Remicade, are biologics, which are large, complex molecules built from living cells rather than manufactured as a simple chemical compound. A pill may not survive digestion intact or may not be absorbed well enough to maximize effectiveness, so the medication is administered through a vein as an infusion or through an injection.

Why more infusions are becoming injections

Many of the most widely used IV biologics now have subcutaneous versions. Darzalex Faspro largely replaced IV Darzalex for new patients after its 2020 approval, and Ocrevus Zunovo now offers an alternative to the twice-yearly Ocrevus infusion. Keytruda has a subcutaneous option, as well.

For patients, the benefits are tangible: 

• Less time in a chair.
• No IV line to place.
• In some cases, fewer reactions. 

When Darzalex moved to its subcutaneous form, it came with a lower rate of the infusion reactions that had made early treatment a slow, closely monitored process.

The need for skilled care regardless of site

Whether a provider-administered drug runs through an IV line or goes under the skin, a licensed nurse should still:

• Administers it.
• Monitor the patient for reactions.
• Follow the prescriber's orders. 

One of the most common misconceptions about home infusion or injection is that the patient is on their own. With Leap, a licensed nurse:

• Comes to the home.
• Administers the treatment.
• Stays with the patient through the visit.

All the while, the prescribing doctor remains in charge of the treatment plan. 

Published research on home-based infusion has found clinical outcomes comparable to hospital-based infusion centers, and for patients with weakened immune systems, avoiding shared waiting rooms and infusion chairs reduces their exposure to infection.

Request an impact analysis now with your own data to understand how a new approach to infusion and injection therapies can help your organization save money. 

About the author

Sofia Shrestha is the Senior Director of Clinical Strategy at Leap. With extensive experience in managing complex pharmacotherapies for specialty and rare diseases, she brings a patient-centered approach to specialty care. Her diverse experience spans specialty pharmacy, home infusion, and ambulatory care, which she draws on to lead Leap's innovative pharmacy programs.