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In the United States, what are often loosely called “generic biologics” are usually biosimilars: FDA-approved medicines highly similar to an existing biologic, with no clinically meaningful differences in safety, purity, or potency. Some biosimilars also receive FDA’s separate interchangeable designation. That can affect pharmacy substitution, but state law governs whether substitution is allowed. Neither designation guarantees a lower price or coverage by a particular insurance plan.
What is a biosimilar?
A biosimilar is a biological medicine shown to be highly similar to an FDA-approved biologic called its reference product. FDA requires no clinically meaningful differences in safety, purity, or potency. FDA describes approved biosimilars as safe and effective biologic medicines; they are not necessarily chemically identical copies in the way people commonly understand small-molecule generic drugs to be.
The Biologics Price Competition and Innovation Act of 2009 created an abbreviated FDA approval pathway for biosimilars and interchangeable biosimilars. The pathway is intended to support competition and expand treatment options. FDA says that competition may help lower costs, but the effect on a patient’s price depends on the medicine, insurance plan, and access arrangements.
How can a biosimilar be used for an injectable treatment?
FDA says a biosimilar and its reference product are administered in the same way and have the same strength and dosage. For biologics, administration can include an injection under the skin (subcutaneous) or an infusion into a vein (intravenous). This is why a biosimilar can be an option for a treatment delivered by injection or infusion.
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That does not establish that every product has an identical device, packaging, or set of patient instructions. Patients should follow the instructions for the specific product dispensed and ask their pharmacist or prescriber about any practical differences.
What does “interchangeable” mean?
Interchangeability is an additional FDA determination for a biosimilar; it is not another word for biosimilarity. Some, but not all, biosimilars are designated interchangeable. FDA explains that an interchangeable biosimilar may, depending on state pharmacy law, be substituted for its reference product at a pharmacy without prescriber intervention.
That designation does not mean every biosimilar can automatically be substituted everywhere. State rules and the product’s current status matter. It also does not itself determine insurance coverage, local stock, or what treatment is appropriate for an individual.
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How to check a biosimilar and its reference product
- Find the product relationship and approval information. Use FDA’s Biosimilar Product Information listing to check which reference product an FDA-listed biosimilar is associated with and review its approval information.
- Confirm licensed biologic status. Check the FDA Purple Book. FDA’s Purple Book FAQ explains the database and its scope.
- Check the specific use and presentation. Confirm the indication and dosage form for the product in question. Do not assume that a biosimilar approval for one use or presentation covers every use or presentation of its reference product.
- Ask about substitution and access locally. A pharmacist can explain applicable state substitution rules; the prescriber can address treatment decisions. Check the patient’s current formulary, pharmacy access, and out-of-pocket cost rather than inferring them from FDA approval.
FDA’s product listing changes over time. For example, its listing has identified Jobevne (bevacizumab-nwgd) in relation to Avastin (bevacizumab), with an April 2025 approval date, and Hercessi (trastuzumab-strf) in relation to Herceptin (trastuzumab), with an April 2024 approval date. Those examples are not a complete or necessarily current list; verify a product’s present approval, indication, dosage form, and interchangeability status in FDA sources.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What biosimilar competition can—and cannot—say about cost and access
FDA says the biosimilar pathway can expand treatment options and potentially reduce costs. That is a possibility, not a promise of savings for a particular patient. FDA approval alone does not establish that a product is covered by a plan, stocked by a local pharmacy, or less expensive out of pocket than another option.
FDA’s patient explainer reports nearly 700 million days of biosimilar therapy and 344 million days of care that patients otherwise may not have received without biosimilar competition. These are cumulative treatment and access figures—not dollar savings, a price comparison, or evidence that every patient can obtain a biosimilar.
What to discuss with your care team
- Which FDA-approved product is being considered, and which reference product is it related to?
- Does the product’s FDA-listed indication and dosage form match the treatment being discussed?
- Is it designated interchangeable, and what state pharmacy substitution rules apply?
- What does the patient’s insurance cover, what is the expected out-of-pocket cost, and can the pharmacy obtain the product?
- Are there product-specific administration instructions or device differences to understand?
Do not change or substitute a prescribed treatment based only on a product label or general information. Discuss treatment decisions with the prescriber and pharmacist.
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