USP Rapid Micro Method Chapters: Are They the Right Validation Approach for Compounders? (Part 1 of 2)

We’re frequently asked when to validate rapid methods using USP chapters <72> and <73> vs <1223>. Let’s work out the answers together.    

The History

Most sterile compounded preparations (for our 503A readers) or compounded sterile drugs (for our 503B readers) require a sterility test.  However, the time it takes to perform the compendial sterility test can significantly eat into the Beyond-Use-Date (BUD), which, simply put, is the useable shelf-life for the medicine.  While Rapid Micro Methods (RMMs) offer the possibility of shortening the time to sterility test results, the compounders pursuing these methods are left with a tricky question: How do we validate them?  

Prior to 2019, there were two main resources for validating RMMs – USP <1223> and PDA Technical Report 33.  In 2019, USP started publishing additional chapters on RMMs.  With multiple USP sources describing RMM validation, everyone is left to use their best judgment on which method to support their validation. However, in a heavily regulated industry, uncertainty is a formidable barrier.  Let’s take a closer look at these USP chapters: 

• USP Chapter <1223> “Validation of Alternative Microbiological Methods”, was first published in 2003 (last updated in 2018). The chapter outlines extensive testing and validation criteria necessary to demonstrate equivalence to the compendial test. When first written, it seemed like only large manufacturers with unlimited resources could bring these methods inhouse. Isn’t there a simplified approach for manufacturers that really need these rapid methods?
• USP Chapter <1071> “Rapid Microbiological Methods for the Detection of Contamination in Short-Life Products – A Risk-Based Approach” was first published in December 2019 and updated in August 2025.  This chapter describes some “wiggle room” for sites to bring in rapid methods when their products were administered before a 14-day sterility test could be completed.  The chapter lists rapid method technologies and provides examples of when they may be appropriate.  However, specific instructions on validation are lacking in this chapter.
• USP Chapters <72> and <73> Respiration / ATP Bioluminescence “…Based Methods for the Detection of Contamination in Short-Life Products” were published in August 2025.  These chapters apply the principles of USP <1071> to provide a new validation approach when using these specific rapid modalities.  

Let’s look at these new USP chapters, which provide a promising, simplified approach to rapid method validation. Are these the best chapters for a compounder to follow?

The case for <72> and <73>

There are statements in USP chapters <72> and <73> that make them seem like the obvious choice for compounders:

• Listed Example: Compounders are listed in <1071> as examples of manufacturers where chapters <72> and <73> may apply.
• Short BUDs: Chapters <72> and <73> are specifically for short-life products.  We know BUDs (i.e., shelf life of compounded products) were significantly shortened for 503A compounders when Chapter <797> was updated in November 2024.  
• Rapid Method Technology: Chapter <72> specifically references CO2 detection methods, and <73> specifically references ATP-based methods.  It is easy to imagine a regulatory inspector coming to your site, seeing your CO2 or ATP based method, and asking to see your validation per <72> or <73>.

With these simple facts laid out, choosing to validate per USP <72> and <73> is extremely compelling.  We also must note the practical bonuses when it comes to validating this way:

The validation workload is simplified. They specifically say you can leverage data that rapid method vendors have already generated. This allows you to start routinely testing with rapid methods faster and at lower validation costs.

The requirements in <72> and <73> provide an opportunity for faster routine time-to-detect.  

Not only does validation per <72> or <73> seem like the obvious choice for compounders, but the validation studies they describe seem easier, less costly, and can lead to faster release times.  This seems too good to be true.  Why would any compounder follow USP Chapter <1223> for their validation?

In their next Eureka Blog post, coming June 15, Erika and Jon describe their understanding of the chapters’ original intentions and how they apply to the current standard in the compounding industry.  Here is a link to the two-part series.