Methods for testing the bioavailability of ear drops

Abstract

Introduction. A very important pharmaceutical parameter in exercising a maximum pharmacological effect is the bi speed of disposal of the active substance by a pharmaceutical form, its absorption in the body, its transport to the site of action and its biological response. Aim of the study. Advanced bibliographic study on the diversity of methods used in the study of bioavailability of ear drops. Materials and methods. 87 abstracts and scientific articles from the Cochrane Electronic Library, MEDLINE databases, CAB Abstracts © and SciSearch © The Thomson Corporation. Results. The bibliographic evaluation of the sources studied has highlighted the importance of the basic physico-chemical characteristics of the drug substances incorporated in the pharmaceutical form, which directly influence the bioavailability. For example: drugs with high molecular weight or high electrical charge cross the blood-brain barrier (inner ear membrane) with passive difficulty, as well as protein-binding substances, while high liposolubility of drug substances facilitates passage. It has been established that there are several methods used to investigate the bioavailability of active principles from ear drops, using Franz diffusion vertical cells. Animal skin is often recommended for preliminary evaluations of new formulations as a membrane for yield. Animal models used to replace human skin are domestic pigs, rats, mice, guinea pigs and snakes. Thus, 26% of the evaluated sources propose the use of the skin of newborn pigs. In most articles (68%) it is proposed to use the skin on the inner side of the pig's ear, as results are comparable to those obtained on human skin due to similar thickness, vascular anatomy and arrangement of collagen fibers in the dermis of the ear, as well as due to the identical glycosphingolipid and ceramide content. The bioavailability assessment is done by determining the concentration of the substances (usually by chromatographic or spectral methods) at equal intervals in the yield medium. Conclusions. Bioavailability is extremely important for the preformulation and drug formulation process, and the correct selection of the in vitro determination method facilitates the correlation of results with those obtained in vivo.oavailability of medicines, which represents the quantity and