“…The administration routes that require less manipulation techniques are recommended [68]. In animal experimentation, several routes for substance administration are currently available, namely enteral (through the digestive tract), either oral (into the mouth) or gavage (esophageal, gastric, nasogastric or orogastric), intravenous (into a blood vessel), epicutaneous (onto the skin), intradermal (into the skin), subcutaneous (under the skin), transdermal (across the skin), intramuscular (into a muscle), transcorneal (onto the eye), intraocular (into the eye), intracerebral (into the brain), epidural (into the dura mater surrounding space), intrathecal (into distal spinal cord surrounding space), intraperitoneal (into the peritoneal cavity), intraosseous (into the marrow cavity), intranasal (sprayed into the nose and then absorbed by the nasal mucous membranes or into the lungs), intratracheal (into the lungs by direct tracheal instillation), inhalation, and other less common techniques, such as those using other body natural orifices, surgical exposure, and others regarding species-specific anatomic features [68,69,70,71,72].…”