Antimicrobial preservatives are added to products to prevent or limit microbial contamination, which can occur during normal conditions of storage and use. Their efficacy can be compromised by formulation, container, or even the active pharmaceutical ingredient itself. This complexity poses a risk, not just to patient safety but to compliance with stringent global regulations. 

The Eurofins BioPharma Product Testing network of laboratories has the capabilities to answer your regulatory and technical needs when it comes to Preservative Efficacy Testing (PET). You can expect testing performed in ISO-certified microbiology labs, stringent environmental monitoring to eliminate contamination risk, state-of-the-art technologies, and expert microbiologists who stay current with evolving pharmacopoeial guidance.

We offer fully compliant, Preservative Efficacy Testing (PET) to assess antimicrobial preservation of pharmaceutical products:

• US : Adapted from USP Chapter <51>, microbial challenge studies are non-compendial studies
• Europe : Preservative Efficacy Test – European Pharmacopoeia 5.1.3
• UK : Guidelines Current BRITISH PHARMACOPOEIA (BP), Appendix XVIC, Efficacy of Antimicrobial Preservation

Our microbiology experts understand the nuanced behaviour of antimicrobial agents in complex products, for example, lyophilized powders that are reconstituted with a diluent or admixtures of liquid products. We design robust challenge studies that evaluate antimicrobial effectiveness over time, under specific storage and usage conditions.

When performing a microbial challenge study, a low level of microorganism is inoculated into the product to simulate contamination during the preparation of a patient’s dose. The challenge microorganisms should include the panel of microorganisms provided in the guidelines above, as well as typical skin microflora and nosocomial organisms. Throughout the study, the inoculated product is removed from the specified storage condition and plated to determine the number of microorganisms present at that time point. At the end of the study, the product’s microbial growth potential is defined as not more than 0.5 log₁₀ increase from the inoculum control concentration.

Microbial challenge studies can provide critical insights into how long drug products can be held before patient safety is at risk. These studies assess the effectiveness of preservatives and/or preservative ingredients, optimum storage conditions, and ultimately, if the drug product formulation can withstand low level contamination. If microorganisms can grow in the final drug product during the holding period, then the intended hold time, product formulation, or storage conditions should be re-evaluated. Eurofins BPT can then support your team in re-assessing and optimising these parameters through expert-led, regulatory-compliant testing.