Biosimilar Switching: What Happens When You Change from Originator

When you’ve been on a biologic drug like adalimumab or infliximab for years, your body gets used to it. Your symptoms are under control. You know how the injection feels. You’ve built a routine around it. Then your doctor says, "We’re switching you to a biosimilar." Suddenly, you’re not just changing a pill-you’re changing the entire experience. And that’s where the real questions start: Will it work the same? Will I feel different? Is this safe?

What Exactly Is a Biosimilar?

A biosimilar isn’t a generic. That’s the first thing to understand. Generics are exact copies of small-molecule drugs like aspirin or metformin. Biosimilars are copies of complex biologic drugs-medicines made from living cells, like antibodies. Think of it like trying to recreate a handmade quilt. You can match the pattern, the thread, the stitching-but there will always be tiny differences in how it was woven. That’s why regulators like the FDA and EMA don’t call them "identical." They call them "highly similar." To get approved, a biosimilar has to go through more than 250 tests comparing its structure, purity, and how it behaves in the body to the original. It must show no clinically meaningful difference in safety or effectiveness. That’s not just marketing speak-it’s science. The first U.S. biosimilar, Zarxio (filgrastim-sndz), was approved in 2015. Since then, 37 have been cleared, mostly targeting conditions like rheumatoid arthritis, psoriasis, and Crohn’s disease.

What Happens When You Switch?

Switching means stopping your originator biologic and starting the biosimilar. This can happen for two reasons: medical switching (your doctor recommends it because it’s a better fit) or non-medical switching (your insurance or pharmacy pushes it to save money). The data shows both are generally safe-but the experience isn’t always smooth.

A major study called NOR-Switch tracked 481 patients switching from originator infliximab to its biosimilar, CT-P13. After one year, 52.6% stayed on the biosimilar. That’s only 7.4 percentage points lower than those who stayed on the original. No big difference. Another study in IBD patients switching from CT-P13 to another biosimilar, SB2, found 90.6% stayed in remission. Their lab markers didn’t budge.

But here’s the catch: people don’t always stop because the drug stopped working. Often, they stop because they feel like it didn’t work.

The Nocebo Effect: When Your Mind Changes Your Body

This is one of the most overlooked parts of biosimilar switching. The nocebo effect is the opposite of the placebo effect. Instead of feeling better because you believe a treatment will help, you feel worse because you believe it won’t.

A 2021 study found that 32.7% of patients reported new or worsening symptoms after switching-even though their blood tests, disease scores, and doctor evaluations showed no change. Reddit threads are full of posts like: "I switched to the biosimilar and my joints started aching again." But when doctors checked their infliximab trough levels? Perfect. No antibodies. No flare.

In one study of etanercept switches, 12.6% of patients discontinued the biosimilar-not because it failed, but because they felt it did. That’s not a drug failure. That’s a perception failure. And it’s why patient education matters more than ever.

Is It Safe to Switch More Than Once?

Some patients end up switching multiple times: originator → biosimilar A → biosimilar B. Is that okay?

The answer, based on current evidence, is yes. The Lauret et al. study followed 140 patients through two switches-from originator infliximab to CT-P13, then to SB2. Immunogenicity (the body making antibodies against the drug) stayed low: just 3 cases per 100 patient-years. Trough levels didn’t drop. Adverse events didn’t increase. The data says: multiple switches are safe.

But real-world data isn’t always so clean. A Spanish study found a 15.3% discontinuation rate after switching between two biosimilars in IBD patients-higher than the 8.7% seen in those who never switched. Why? The researchers couldn’t pinpoint a biological reason. Trough levels were the same. Antibodies didn’t spike. It’s possible that repeated switches amplify anxiety, which then triggers symptoms.

Cost Savings and Access: Why This Matters

Biosimilars cost 15% to 35% less than the original biologic. Humira’s biosimilars launched at a 35% discount in 2023. That’s billions saved for insurers-and more patients who can actually afford treatment.

In Europe, 67% of filgrastim prescriptions are biosimilars. In the U.S., it’s only 24% for infliximab. Why the gap? Patent strategies, rebate deals, and slow adoption by some providers. But by 2023, 85% of U.S. health plans had mandatory switch policies. That means if you’re on a biologic, you’re likely to be switched eventually.

The goal isn’t just to cut costs-it’s to expand access. Without biosimilars, many patients would never get treated at all.

When Switching Might Not Be a Good Idea

Switching works best when your disease is stable. If you’re in remission with a DAS28 score under 3.2 (for rheumatoid arthritis) or your Crohn’s is quiet, you’re a great candidate.

But if you’re actively flaring, recently changed doses, or have had multiple treatment failures? Hold off. The evidence isn’t strong enough to recommend switching during unstable disease. The FDA Adverse Event Reporting System has recorded rare cases of flares after switches-but those are outliers. Most flares happen regardless of the drug used.

Also, avoid switching if you’ve had a serious reaction to the originator. That’s not a biosimilar issue-it’s an individual sensitivity. Talk to your doctor before any switch.

What Doctors Should Do Before Switching

A good switch isn’t automatic. It’s a conversation. The PERFUSE study showed that when patients got a 20-minute counseling session before switching, discontinuation dropped from 18% to just 6.4%. That’s huge.

Here’s what works:

• Explain what a biosimilar is-no jargon. "It’s like a copy of your current medicine, made to work the same way."
• Share the data: "Studies show most people do just as well."
• Ask: "What are your concerns?"
• Set up a 3-month check-in to monitor symptoms and lab values.
• Don’t just hand over a prescription-offer support.

What Patients Should Know Before Switching

You’re not just a patient. You’re a partner in your care. Here’s what you need to do:

• Ask: "Is this switch medically necessary, or just for cost?"
• Request your current drug levels and antibody tests before switching.
• Track your symptoms in a journal-note energy, pain, bowel habits, skin changes.
• Don’t panic if you feel "off" in the first few weeks. Give it time.
• If you feel worse after 8-12 weeks, talk to your doctor. Don’t assume it’s the drug.
• Know your rights. In some places, you can opt out of a non-medical switch.

The Future of Switching

The first interchangeable adalimumab biosimilar, Cyltezo, got FDA approval in 2024. That means pharmacies can swap it for the originator without asking your doctor. It’s a big step toward convenience-but also a bigger responsibility for patient education.

Long-term data is still growing. The NOR-SWITCH II study showed 89.2% of patients stayed on treatment after two years of multiple switches. That’s encouraging. But we’re still learning.

The bottom line? Switching from originator to biosimilar is safe for most people. It’s not perfect. It’s not risk-free. But the science says: the benefits far outweigh the risks-for your body, your wallet, and the future of care.