Quats as Excipients for Preservation
Quaternary ammonium compounds (Quats) can be used to destroy or prevent the growth of bacterial, fungal or algae cells. This is done through physical disruption and partial solubilization of the organism's cell wall and membrane.
Preservation in Pharmaceutical and Cosmetic products is of great importance.
The term preservation refers to the action of adding a substance to a product in order to prevent its deterioration and/or decomposition due to chemical or bacterial action.
The presence of water in pharmaceutical (human or veterinary) and cosmetic (personal care) formulations is the pre-condition for microbial growth. Water used in the formulations may be contaminated by harmful micro-organisms such as Pseudomonas, Enterobacteria, Bacillus, Streptomyces, Aspergillus. Microorganisms need nutrients to grow, most commonly C, O, H and N. Microorganisms have two effects.
Microorganisms can:
- cause degradation of formulations
- be harmful to the consumers
Degradation of formulations may involve discoloration, development of unpleasant odours, breaking of emulsions and visual degradation due to the formation of colonies of fungi and bacteria. In dry powders, the presence of dextrin or starch can favour the development of yeasts, moulds and Clostridia. The Oil-in-Water (O/W) formulations are the ones demanding the highest level of protection because they offer the most favourable media for the development and growth of microorganisms in terms of pH, nutrients and water content. But most importantly, cosmetic or pharmaceutical product contamination can have severe consequences for their users.
Healthy human skin hosts a broad variety of gram positive microorganisms, mainly Staphylococcus strains. A healthy skin has a self-defense mechanism that protects it from the infection from normal levels of pathogenic microorganisms. The problem arises if products carrying infecting microorganisms come in contact with degraded (unhealthy, wounded) skin, as this can cause allergies and infections.
Even if the pharmaceutical or cosmetic manufacturer puts products on the market that are free from microbial contamination, this does not guarantee full protection since when the package is open, the formulation may be exposed to non-hygienic environments, with the consequent risk of re-contamination.
