Page 58 - MNU-PM502- Pharmaeutical Microbiology Theoritical Book

Pharm D- Clinical Pharmacy Program Third Level Pharmaceutical Microbiology& Antimicrobials (PM 502)

Factors affecting preservative efficacy

1) Interaction with the formulation components:

Hydrocolloids such as methylcellulose, PVP, alginates, and tragacanth can interact
with preservatives and diminish their activity.

2) Properties of preservatives:
- The distribution of the preservatives must be homogeneous and more solubility in

the bulk phase is preferable in a multiphase system.
- Preservatives may react with substances leaked from the container and lose their

antimicrobial activity.
3) Effect of containers
- Formulations packed in a glass container can be expected to retain their preservative
content if the closure is airtight.

- Preservatives may penetrate through the plastic containers and also react with
closures.
4) Types of microorganisms:

- Plant products may contain pathogenic microorganisms from the soil e.g.
Clostridium species, and Bacillus anthracis
- Soil organisms are common in dust which may gain access to preparation during

processing or packing.
5) Influence of pH:
- Adjustment of the pH of the solution may affect the chemical stability and the

activity of the preservative.

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