In most cases, introduction of the tube toward the rear of the mouth will induce swallowing and the tube will readily enter the esophagus. If introduced from the left diastema the needle should be directed caudally toward the right ramus of the mandible. As the needle approaches the pharynx the mouse will usually swallow allowing introduction into the esophagus. With the stomach tube fitted to a syringe or aspirator, materials may be administered or withdrawn as required. Sites used for collection of blood from veins may also be used for intravenous administration.
Intraperitoneal administration is one of the most frequently-used parenteral routes in rodents.
Other locations are the musculature and subcutis. Materials given intramuscularly must be in very small volumes and is generally not recommended unless necessary. Absorption by this route is more rapid than from subcutaneous administration. Regardless of the route used, it is essential that the subject be securely restrained to prevent unnecessary struggling by the animal and to avoid injury to personnel by dislodged needles. Considerable tissue damage and discomfort can be caused by irritating vehicles, drugs or solutions when injected into animals.