Non-Surgical Endodontic Treatment consists in the removal of dental pulp and the elimination of microorganisms that cause infection of the pulp space. This treatment can be performed in a single or in multiple sessions and, sometimes, the use of Intracanal Medication may be necessary.The purpose of Intracanalar Medication is to reach bacteria present in places inaccessible to instrumentation or irrigants and, also, to inhibit the invasion of the root canal system by bacteria or its products by coronal, lateral or apical communications with the outside through dentinal tubules, apical foramen or accessories root canals.The present work is a narrative review of the Literature that aims to analyse the different opinions among authors, in the case of permanent mature teeth with diagnosis of necrosis with or without apical periodontitis associated, and to understand in which situations it is necessary to apply Intracanal Medication, which should be chosen and how it should be applied. In this way, it is also intended that this work can be a useful guide for clinicians.