Interchangeability and switching

Moving patients to biosimilar treatments.

‘Switching’ and ‘automatic substitution’ are often mentioned in the context of changing patients from a biologic to a biosimilar. The main difference between the two is that ‘switching’ must be either instigated or approved by the prescriber whereas ‘automatic substitution’ can theoretically be done without the knowledge of the prescriber if the product has been designated as interchangeable by the FDA.1,2


This is the decision by the treating physician to switch patients from a biologic to a biosimilar, or vice versa. Unless the biosimilar is designated as interchangeable, switching must always be approved by the treating physician.1

Automatic substitution

A pharmacist substitutes a prescribed product with another interchangeable product without consulting the prescriber.2

Interchangeable biosimilars in the U.S.

As of June 2021, there are no biosimilars in the U.S. that have been designated as interchangeable.3 To achieve this status, additional studies are needed to demonstrate that:3-5

  • The biosimilar produces the same result as the reference product in any patient, and
  • Any type of switching of products does not result in safety risk or diminished efficacy compared to the reference product


  1. Barbier L et al. The efficacy, safety, and immunogenicity of switching between reference biopharmaceuticals and biosimilars: A systematic review. Clin Pharmacol Ther. 2020;108(4):734‒755.
  2. Declerck P et al. The language of biosimilars: Clarification, definitions, and regulatory aspects. Drugs. 2017;77(6):671‒677.
  3. Dalpoas SE et al. Barriers to biosimilar utilization in the United States. Am J Health-Syst Pharm. 2020;77(23):2006‒2014.
  4. Alvarez DF et al. Interchangeability of biosimilars: What level of clinical evidence is needed to support the interchangeability designation in the United States?. BioDrugs. 2020;34(6):723‒732.
  5. FDA. Published 2015. Accessed May 5, 2021.

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