Intravenous (iv) directly into the vascular system through a vein
Intraperitoneal (ip) - - into the abdominal cavity
Subcutaneous (sc) - - under the skin
Intramuscular (im) - - into a muscle
When drugs, vaccines, injectable anesthetics or other agents are to be administered, one of several different routes may be selected. The route is governed by the nature of the agent being administered, the animal, and the purpose of the administration, among other factors.
Oral: Substances may be administered orally by addition to the food or the drinking water. The amount of drug consumed by an animal will vary between each individual. If the drug imparts an unpleasant taste, affecting palatability, the drug will be consumed in decreased amounts. Also, environmental conditions such as the ambient temperature will also affect both water and food consumption. The general rule of thumb is that 15 grams of food and 15 mls of water will be consumed daily per 100 grams of body weight. 5
Gavage: If it is necessary to administer exact amounts of a substance gastric feeding needles should be used. Entry normally may be obtained without anesthesia using hand restraint. Feeding needles with a ball tip helps prevent introduction of the needle into the trachea and prevents trauma to the oral cavity (picture). Flexible or plastic tubes may be bitten or chewed and are not recommended for rodents. Feeding needles are inserted through the mouth into the stomach or lower esophagus. Placing the needle next to the mouse so that the end of the needle is adjacent to the last rib and marking the position on the needle that is adjacent to the tip of the nose will determine the distance the feeding needle should be advanced into the oral cavity to insure administration of the compound into the stomach (picture). Care must be taken that the tube or needle does not enter the trachea or puncture the esophagus or stomach, therefore knowledge of the oropharyngeal anatomy is necessary. In most cases, introduction of the tube toward the rear of the mouth will induce swallowing and the tube will readily enter the esophagus. A violent reaction (coughing, gasping) usually follows accidental introduction of the tube into the larynx or trachea. With the mouse restrained in one hand the feeding needle is introduced in the space between the incisors and the beginning of the molars (diastema)(picture). 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. Using the feeding needle to gently extend the neck facilitates introduction into the stomach (future video). With the stomach tube fitted to a syringe or aspirator, materials may be administered or withdrawn as required.
Intravenous (iv) - - directly into the vascular system through a vein
Intra-arterial (ia) - - directly into the vascular system through an artery
Intraperitoneal (ip) - - into the abdominal cavity
Subcutaneous (sc) - - under the skin
Intramuscular (im) - - into a muscle
Intradermal (id) - - between layers of skin
General Considerations: Parenteral routes of administration involve injections into various compartments of the body. 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.
The investigator should know the physiological and chemical properties of the substance that he/she plans to inject. Considerable tissue damage and discomfort can be caused by irritating vehicles, drugs or solutions when injected into animals. The use of the foot pad as an injection site for antigens with or without adjuvant is discouraged since it is a needless and painful procedure. More suitable sites for antigen injections are subcutaneously in the axilla or lateral thoracic wall, deep in large muscle masses, or into the popliteal lymph node.
Demonstration/instruction sessions can be arranged with the ACU.
Equipment: 27-30 g needle, 1 ml tuberculin syringe, mouse holder, warming lamp.
Volume: The volume injected IV into an adult mouse should not exceed 0.2 ml.
The lateral veins of the tail are the most frequently-used veins. Best results are obtained if the tail is immersed in warm water for 5 to 10 seconds or the mouse warmed for 5 to 15 minutes in the cage with a warming lamp with a 40 to 100 watt bulb. The veins can be seen when the tip of the tail is lifted and rotated slightly in either direction. The tip of the needle can be followed visually as it penetrates the vein. Trial injection verifies proper needle placement. Also, accurate placement can be confirmed when the vessel is visually flushed when the compound is administered. The formation of a bleb at the site indicates improper placement of the needle. A second attempt can be performed by removing the needle and trying a site on the same vessel in a more proximal location on the tail. Practice is essential.
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