Preservative Efficacy Testing

Preservative Efficacy Testing is performed to determine the minimum effective concentration of preservative required in a product to meet the specifications set out in the Pharmacopeia’s for pharmaceutical formulations i.e. creams, syrups, liquids etc

Positive cultures required to challenge a pharmaceutical preparation:

  • Staphylococcus aureus
  • Pseudomonas aeruginosa
  • E-coli
  • Candida albicans
  • Aspergillus brasiliensis

A preservative efficacy test is performed by challenging the preparation preservative system, by spiking the preparation with positive cultures at the specified levels (105 to 106Cfu/ml /g) and testing the spiked preparation at a number of time points over a 28 day period as specified in the pharmacopoeia. Each time point is used to determine the level of positive culture remaining in the preparation at that time point and based on a reduction in the levels at each time point over the 28 day period it can be determined if the preservative system is effective or not in the pharmaceutical formulation.

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