The present thesis was elaborated aiming to obtain the master’s degree in pharmaceutical sciences. In here, it is described all the scientific investigation work done to reach the proposed objective, as well as all tasks and learnings that I have taken along my community and hospital pharmacy internships. Chapter 1 is related with my scientific investigation work entitled “Bioanalytical method validation of Venlafaxine and Desvenlafaxine in mouse plasma, brain and liver using a MEPS/HPLC assay: a path to study these drugs’ intranasal administration”. Since major depressive disorder is one of the most prevalent psychiatric diseases, its therapeutic successful rate must be increased. Nowadays, the majority of all antidepressants used are give...