Transdermal absorption is the process of absorption of a substance into the bloodstream through the skin. The process itself is highly complex mostly due to the complexity of the structure of the skin. Because of all the advantages that transdermal absorption has, it is necessary to encourage the progress of this field. We were especially interested in learning how the data from in vitro measurements and from in vivo studies was acquired and how it is presented in the literature. Therefore we reviewed the literature on transdermal absorption of three non-steroidal anti-rheumatic agents: ibuprofen, ketoprofen and diclofenac. These agents were chosen because of their long-known use via transcutaneous application. We searched for the articles in the Pubmed database and focused on those where researchers worked with human volunteers, or they used human skin for their work. Research where animal models and artificial membranes were used was also included. By reviewing the relevant articles of both types of models. We organized the data on absorption and permeability for these non-steroidal anti-rheumatic agents obtained from different types of models and methods. We found that there was a high variability and inconsistency in experimental design, especially in the choice of different methods or materials in in vitro studies. This is especially noticeable when using synthetic membranes, which were found not to yield relevant results. In vivo studies on volunteers also had some limitations, such as a lack of use of non-invasive methods and time-consuming procedures. We observed that to improve the relevance of the obtained data from the perspective of in vitro – in vivo correlation, future studies should aim to use more standardized methods and materials for both in vitro and in vivo experiments. This would benefit their usefulness in the registration procedures and quality control of final pharmaceutical forms
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