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Application of Human Factors Engineering Principles for Combination Products

— Questions and Answers Guidance for Industry and FDA Staff.

In September, 2023, FDA released their guidance ‘Application of Human Factors Engineering Principles for Combination Products: Questions and Answers’.

This guidance finalizes the February 2016 draft version entitled ‘Human Factors Studies and Related Clinical Study Considerations in Combination Product Design and Development’. It specifies FDA’s expectations for certain aspects specifically related to human factors engineering for combination products such as identification of critical tasks, considerations for combination products due to the use of drug and device constituent parts together, and training as part of the user interface just to name a few.  

In addition to that, a total of 15 questions and answers are listed aiming to provide clarity through practical examples. 

Guidance Highlights ​

The 2016 FDA guidance: Applying Human Factors and Usability Engineering to Medical Devices [1] reflects HFE principles that are also applicable to the combination product as a whole. However, there are two unique definitions for combination products:  

Final finished combination product

The product intended for market and submitted in the marketing application. That includes the user interface for the combination product (.e.g., proposed packaging, labels and labeling, and training, if applicable) 

Combination product critical task

– Similar to the definition of critical tasks in the 2016 draft guidance [2], “a combination product critical task is a user task which, if performed incorrectly or not performed at all, would or could cause harm to the patient or user, where harm is defined to include compromised medical care.” Compromised medical care includes consideration of medication errors. This definition is different from the definition in Applying Human Factors and Usability Engineering to Medical Devices [1] due to the unique use-related risks associated with the combination product as a whole that do not exist for the device constituent parts alone or the drug alone. FDA is particularly interested in the assessment of tasks that directly: 

  1. Impact dosing (e.g., overdose, underdose, or missed dose), including those that may lead to lack of treatment response.
  2. Impact administration of the product (e.g., wrong site of administration, improper preparation of drug/biologic before administration) 
  3. Have the potential to result in harm (e.g., physical injury, adverse events, events that may need patient monitoring to confirm no harm, or events that may lead to hospitalization)


For time-sensitive or time-urgent products (e.g., emergency-use autoinjector), most or all tasks are likely critical tasks. 


Drug properties can affect users’ interactions and need to be considered when identifying, evaluating, and managing the use-related risks for the combination product. There may be use-related risks associated with the combination product as a whole that do not exist for the device alone or the drug alone. (e.g. high drug viscosity could increase injection delivery time)


– A comprehensive URRA (use-related risk analysis) should be used in the identification of combination product critical tasks. The Agency recommends to submit it as a separate risk analysis and not as a part of the full engineering risk analysis. When modifying combination products, URRA should include all aspects of the combination product to be modified and all elements of the combination product that may be affected by these modifications. 


– Consider using HF actual-use validation study (patients receiving actual medical care) for cases when simulated-use test methods are otherwise inadequate to evaluate users’ interactions with the final finished combination product. Note that HF actual-use validation studies should not be confused with other clinical studies with broader scopes. 

The 15 questions answered in the guidance are:

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Our Senior Human Factors Specialist, Morten, is looking forward to discuss the impact of this guidance. Send him a note or give him a call. He is looking forward to hear from you.

Morten purup hansen, writer of FDA submission article
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