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Microbial Contamination Risk Levels and Beyond-Use Dating



According to USP <797>, CSPs are assigned primarily according to the potential for microbial contamination during compounding. Potential sources of contamination include, but are not limited to, solid and liquid matter from compounding personnel and objects; non-sterile components employed and incorporated before terminal sterilization; and inappropriate conditions within the restricted compounding environment.

Beyond-Use Date is the date and time after which a CSP shall not be stored or transported. It is determined from the date or time the preparation is compounded. This is also known as Discard afterUse before or Administer by.


Risk Level Ingredient : CSP Ratio Beyond-Use Date
Controlled RT Refrigerator Freezer


48 hours 14 days 45 days

One : Many or Many : One

30 hours 9 days

Any ingredient-CSP relationship using nonsterile ingredients and/or devices that requires terminal sterilization

24 hours 3 days


The proposed USP <797> revisions collapsed CSP microbial risk categories from three to two and changed terminology. No sterile compounding is inherently "low risk" and preparation of all CSPs must be done carefully. Categories were renamed neutrally and are distinguished primarily by the conditions under which they are made.


Risk Level Description Beyond-Use Date
Controlled RT Refrigerator
Category 1

PEC placement, Sterility Testing and Endotoxin Testing are not required

≤12 hours

≤24 hours
Category 2

PEC is placed in ISO classified air, Sterility testing is based on assigned BUD, Endotoxin testing is not required if with sterile components

≥12 hours

≥24 hours


CSP - Compounded Sterile Preparation; PEC - Primary Engineering Control; RT - Room Temperature


All personnel handling CSPs should be well aware of the best practices and prevailing regulation.

It is now time to address USP <797>!


1. USP <797> Pharmaceutical Compounding - Sterile Preparations
2. USP <797> Proposed Revision (September 2015)


Esco isolators offer improved sterility assurance for the product and an effective protection of the healthcare personnel against risks caused by hazardous substances.

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