Guidelines for Injection Methods

Guidelines for Maximal Injection Volumes

Guidelines for Injections Sites, Volumes, & Needle Gauges

Injection Methods: Various routes of injection are useful in laboratory animals. The route chosen will depend on the species, volume of sample, material to be injected and desired rate of absorption:

  • Intraperitoneal: This is a commonly used method for small rodents since they do not have readily accessible veins. Intraperitoneal injections should be given in the lower left or lower right quadrant of the abdomen because vital organs are absent in this area. To prevent injection of intestine, only the tip of the needle should penetrate the abdominal wall.

  • Subcutaneous: In most laboratory animals the most convenient site for injection is the back of the neck. A fold of skin behind the neck is held between the fingers and a needle threaded under the skin at the base of the fold.

  • Intramuscular: The most commonly used site for intramuscular injection is the thigh muscle. Quadriceps, rather than posterior thigh muscles, should be used for injection of irritating substances or larger volumes.

  • Intravenous: Intravenous injection of tail veins is frequently used for small rodents. Animals should be properly restrained. Warming of the tail is useful to increase blood flow. A 26 gauge needle or smaller is used for venipuncture in mice and a 20 gauge needle or smaller in rats. Injection of tail veins is generally accomplished by compression of the lateral tail vein by applying pressure at the base of the tail. In rabbits, ear veins, tarsal veins or cephalic veins are common sites for intravenous injection. Ear veins are also a useful site in guinea pigs.

  • Intradermal and intra-arterial injections are discouraged and require justification from the investigator.

  • Intrathecal injections require general anesthesia.

  • Footpad injections are discouraged and require Duke University IACUC approval.