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Preservative Efficacy Test (PET) or Antimicrobial Effectiveness Test (AET)

Preservatives are routinely added to pharmaceuticals, devices, cosmetics and personal care products to prevent, or limit microbial contamination that can occur during storage and normal use of the product.

The effectiveness of antimicrobial preservation must be demonstrated for each formulated product and in each container and closure system.  As preservation protection may diminish over time and during use of multi-dose packs effectiveness of antimicrobial preservation must be demonstrated over the shelf life of the product.

Testing requirements are detailed in BP, Ph.Eur, USP and ISO11930.  Product is inoculated with specific organisms to simulate possible contamination (challenge organisms) and incubated for a period of 28 days.  Samples are taken at various intervals and tested to determine the number of surviving viable organisms.

The number or organisms and testing intervals will depend on the type and route of administration of the product. Preservation is considered adequate if there is no increase, or a reduction of the number of viable organisms over the storage time.


  • Pharmaceuticals
  • Biologics & Biopharmaceuticals
  • Medical Devices
  • Beauty, care and wash

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