Having found a potential drug, it has to be transported to the site of action. This involves the crossing of several biological barriers. The first barriers are already encountered when absorbing the drug into the human body. Here, the intestinal wall or the membrane of the lung vesicles has to be permeated, before the drug can be degraded or excreted.
In addition, losses during the drug transport have to be taken into account. Even when trying to interfere with primitive (single-cell) organism, at least the cell membrane has to be crossed. Here, first of all, the practical experiment is necessary - a costly and time-consuming procedure for testing the efficacy of a drug candidate.
In this section, much research has to be done, especially in the areas of bioinformatics to provide alternative methods that may help saving time and money in the drug development.