Introduction
Changing an antimicrobial regimen has shown to influence the emergence of antimicrobial resistance, in which the regimen consists of the dose, the treatment interval, the duration of therapy, and the formulation. There is substantial evidence to encourage the use of high dose as short as possible, with a small and regular treatment interval to minimise the risk for the selection of resistant mutants. However, in contrast with these first three aspects of the antimicrobial regimen, little attention is currently paid to 'formulation' in relation to guidelines for a rational antimicrobial therapy to maintain clinical efficacy while reducing the opportunity of resistant strains to have a selective advantage. Formulations of antimicrobial agents have been adjusted in function of the route of administration, which can be local (topical) or systemical. Systemical concentrations of a certain antimicrobial molecule can be achieved either through oral, sublingual, rectal or injectable administration.