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In the United States, what people may casually call a “generic” injectable biologic is usually a biosimilar—a medicine highly similar to an FDA-approved biologic, with no clinically meaningful differences in safety, purity, or potency. Some biosimilars also receive a separate FDA designation as interchangeable, but that does not mean every product can be substituted automatically at every pharmacy.
What is a biosimilar?
A biosimilar is a biological medicine shown to be highly similar to an already approved biologic, known as its reference product. FDA says there are no clinically meaningful differences between the biosimilar and reference product in safety, purity, or potency. FDA describes approved biosimilars as safe and effective biologic medicines; they are not chemically identical copies in the way people often mean when they talk about generic versions of conventional small-molecule drugs. FDA’s patient explainer provides the agency’s definition.
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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; it does not make the products identical or guarantee a particular price. FDA explains the pathway and its competition goals.
Why can an injectable or infused biologic have a biosimilar?
Biosimilar medicines can be given by the same route as their reference products, including subcutaneous injection or intravenous infusion. FDA says they have the same strength and dosage as the reference product and are administered in the same way. That does not establish that every brand’s device, packaging, or patient instructions are identical, so patients should follow the instructions for the specific product they receive.
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What does “interchangeable” mean?
Interchangeability is an additional FDA determination for a biosimilar; it is not another word for biosimilarity. Some biosimilars are interchangeable and some are not. Where state pharmacy law permits, an interchangeable biosimilar may be substituted for its reference product at a pharmacy without the prescriber intervening. The applicable state rule matters, and FDA designation alone does not mean a product may be substituted everywhere.
How to check a specific medicine
Approvals and interchangeability status are specific to products and can change. Confirm the relationship and status for the exact medicine rather than assuming that every biosimilar has the same uses, presentation, or substitution rules.
- Search FDA’s Biosimilar Product Information page for the product and its reference product. Check approval date, indication, and dosage form.
- Use FDA’s Purple Book to verify licensed biological product status. FDA’s Purple Book FAQ explains what the database covers.
- Check whether FDA has designated the specific biosimilar interchangeable, then confirm the pharmacy substitution rule in the relevant state.
- Ask the prescriber or pharmacist about the product’s route, strength, dosage, device instructions, and whether a proposed change is appropriate for your treatment.
- Ask the insurer and pharmacy about the exact product’s formulary coverage, local availability, and your out-of-pocket cost. FDA approval does not establish that a product is stocked locally or preferred by a particular insurance plan.
For example, FDA’s product listing identifies Jobevne (bevacizumab-nwgd) as a biosimilar to Avastin (bevacizumab), with an April 2025 approval date, and Hercessi (trastuzumab-strf) as a biosimilar to Herceptin (trastuzumab), with an April 2024 approval date. Those examples illustrate why product-level checks matter; an approval date alone does not tell you whether a product is covered, available, or interchangeable for a particular use.
Can biosimilars lower costs or improve access?
FDA says biosimilar competition may lower costs and increase treatment options, but savings are not guaranteed for an individual medicine, insurer, or patient. Actual prices, coverage, and availability depend on the product and payer and should be checked directly.
FDA’s 2025 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 measures—not dollars saved, a price comparison for a particular drug, or proof that every patient can obtain a biosimilar. FDA’s explainer provides the figures and their framing.
What patients should do before a switch
Do not change a biologic treatment or assume that a pharmacy substitution is allowed based solely on the word “biosimilar.” Confirm the exact product, its FDA status, state substitution rules, insurance coverage, and instructions with your prescriber or pharmacist. The right option depends on the specific medicine and the patient’s circumstances.
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