Summary.

The addition of preservatives prevents undesirable changes of the composition and quality of the drugs and assures the duration of their medicinal effect until their expiration date. There are three aspects of the modern understanding of preservative action – to protect the drugs against microbial pollution, to stabilize drug consistency and to avoid undesirable chemical processes. The concentration of the drug preservatives has to be on the one hand adequate to the aim there are in use and on the other hand to be safe. The utilization of the preservatives in the drugs is regulated by the Health legislation, as the preservatives belong to the so called hazardous substances. The proper selection of preservatives added to pharmaceutical products helps to prolong shelf life and maintain sterility and also to avoid undesirable effects to the human health.