Biosimilar Substitution: A Primer for Pharmacists


With biosimilars set to enter the US health care market, pharmacists will soon have new factors to consider when selecting and dispensing products.

With biosimilars set to enter the US health care market, pharmacists will soon have new factors to consider when selecting and dispensing products.

For those unfamiliar with biosimilars and their potential interchangeability, researchers from the University of New England College of Pharmacy recently outlined important issues and considerations in the Journal of Managed Care & Specialty Pharmacy.

Unlike generics of small-molecule drugs, the authors wrote, biosimilars are manufactured using unique living cell systems and processes that cause slight structural alterations from the reference biologics, which could lead to variances in clinical response.

This disparity is the essential difference between generics, which are identical to brand-name medications, and biosimilars, which are similar but not identical copies of biologics.

Given this distinction, the researchers noted, biosimilars have a different regulatory pathway than generics. To receive FDA approval, manufacturers must show that the biosimilar is “highly similar” to the reference product, omitting minor differences in clinically inactive components. They must also demonstrate that, compared with the reference biologic, there are no clinically meaningful differences in terms of safety, purity, and potency.

In addition to approval, a biosimilar may receive an added interchangeability designation from the FDA, allowing it to be substituted for the reference biologic at the point of dispensing without the prescriber’s involvement. Because of this, biosimilars with this designation are ideal candidates for pharmacist substitution akin to generics, the authors explained.

When approaching such interchangeable biosimilar substitution, pharmacists should consider the following questions, which the researchers based on the current process for generic substitution:

  • Does state law give pharmacists the authority to autonomously substitute interchangeable biosimilars, or will the prescriber need to be contacted?
  • What criteria define which products may be substituted?
  • Is the biosimilar considered interchangeable with the prescribed product for all indications? If not, what indications can be substituted?
  • Does the state require prescriber and/or patient notification or counseling?
  • Does the state require record keeping of drugs dispensed and any related notifications of dispensing or substitutions?
  • Is the patient being switched from one product to another? If so, are there any differences in packaging, excipients, devices, or other issues that require counseling?
  • What is the scope of state legislation on substitution of interchangeable biosimilars by pharmacy practice setting?

“It is important for pharmacists to be at the forefront of dispensing medicines and to stay apprised of their respective state laws for information regarding the autonomous substitution of interchangeable biologics,” the authors wrote. “The clinical judgment of pharmacists is paramount in ensuring the safe and effective use of biologics.”

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