ABSTRACT
Surfactant solubilized preparations and multiple-phase formulations such as emulsions, creams and suspensions can pose problems in antimicrobial preservation. Partitioning or adsorption of the biocide to formulation components or the container will also result in a lowering of the aqueous phase concentration, the resultant effect being loss of preservative activity. Glass has largely been replaced by plastics as a packaging material for pharmaceuticals. The presence of contaminating organisms at the surface of glass containers even in the presence of antibacterials represents a serious potential problem. Plastic containers from different manufacturers are likely to show varying preservative adsorption characteristics despite having the same plastic material as the primary component. Co-solvents such as the alcohols, ethanol, propylene glycol and glycerol, can be used to solubilize drugs in aqueous solution. Liposomes have been exploited as carrier systems for drugs, both with injectable and topical preparations. A bactericide is partitioned between the oil and water according to the partition coefficient, and the oil-to-water ratio.
