www.fda.gov Prescribing Interchangeable Products | 1

Prescribing Interchangeable Products

Can interchangeable products be 

substituted for reference products 

by pharmacists?

Once interchangeable biological products are available in 

the United States, some states may permit a pharmacist 

to substitute an interchangeable product for the reference 

product without consulting the prescriber—a practice 

commonly called pharmacy-level substitution. 

Many states have laws that address pharmacy-level 

substitution, and the specific laws vary from state to state. 

For information about prescription and substitution laws, 

check with your state pharmacy board. 

Should a health care prescriber be 

concerned if his/her patient receives 

an interchangeable product in place 

of the prescribed reference product? 

Prescribers and patients can expect that the 

interchangeable product will have the same clinical result 

as the reference product. Prescribers and their patients 

can be assured that an FDA-approved interchangeable 

product has been thoroughly tested and has met FDA’s 

high standards for approval. Meeting these standards 

means that health care professionals and patients 

can be assured of the safety and effectiveness of an 

interchangeable product, just as they would be for a 

reference product.

What approval standards do 

interchangeable products have 

to meet?

A manufacturer of a proposed interchangeable product 

must show that the product is biosimilar to a reference 

product and that it can be expected to produce the same 

clinical result as the reference product in any given 

patient. The manufacturer must also demonstrate that, 

for a product administered to a patient more than once, 

there is no additional risk or reduced efficacy if a patient 

switches back and forth between an interchangeable 

product and a reference product, compared to using the 

reference product without switching.

Although there are distinct approval requirements for 

reference products, biosimilars, and interchangeable 

products, the approval standards that apply to each type 

of biological product assure prescribers of the safety 

and effectiveness of each type of product. All biological 

products are approved only after they meet FDA’s 

rigorous approval standards. 

Can an interchangeable product 

be used in patients who have 

previously been treated with the 

reference product? 

Yes, interchangeable products can be used in patients who 

have previously been treated with the reference product 

(treatment-experienced), as well as in patients who have 

not previously received the reference product (treatmentnaïve). As part of the approval process for interchangeable 

products given more than once, manufacturers must show 

that patients can be switched back and forth between 

the reference product and the proposed interchangeable 

product without an increased risk in terms of safety or 

diminished efficacy. 

Where can you find more information 

about interchangeable products? 

FDA’s “Lists of Licensed Biological Products with Reference 

Product Exclusivity and Biosimilarity or Interchangeability 

Evaluations,” known as the “Purple Book,” is an online 

resource for health care professionals and patients to 

locate information about approved biological products. 

The Purple Book provides information about whether a 

biological product is a reference product, biosimilar, or 

interchangeable product. 

Product-specific information, including a summary of FDA’s 

review of the data that were used to support approval of a 

biological product, can be found at the Drugs@FDA website. 

You can also visit www.fda.gov/biosimilars.