SOP 10.9 - Intradermal Injection in Rats

1. Introduction and Definitions:

The injection methods described within an Animal Use Protocol (AUP) must be followed at all times. The following guidelines provide recommended injection sites, needle sizes and maximum dose volumes. “Good Practices” include:

• All animals securely and safely restrained prior to injecting.
• Only three attempts per site should be practiced. If unsuccessful, allow another (trained and competent) person to collect the sample.
• Use the appropriate gauge needle and volume for the injection site based on the size of the rat.
• Before injecting any substance, aspirate first to ensure appropriate placement of the needle (excluding intravenous injections).
• Always inject with the bevel up on the needle.
• Always ensure the substances you are injecting are sterile, and use sterile technique.
• Every animal requires a new sterile syringe and a new sterile needle. With small volumes, it is preferable to dilute the injectable agent to a 50% or less solution to ensure accurate dosing.
• Disinfecting the skin with alcohol is mandatory for intravenous, intraperitoneal, intramuscular, intradermal, and all biohazardous injections.
• Choose the appropriate administration route for the substance to be injected.

2. Materials:

• Restrainers and drapes as required
• Sterile syringes
• Sterile needles (21-27 gauge)
• 70% alcohol
• Clippers
• Injectable solution
• Anesthetics as required (if using anesthetics: eye lubricant, heating source, Isotonic fluids – see SOP 10.6 Anesthesia in Rats)

3. Procedures:

• Every animal requires a new sterile syringe and a new sterile needle.
• Load the syringe and needle with appropriate volume to be injected.
• Safely restrain the animal on the table.
• The hair may need to be shaved to allow for better view.
• Disinfect the injection site with 70% alcohol (if practical).
• Pinch the skin upward or lay the syringe with bevel facing upward along the side of the animal’s body.
• Insert the needle just burying the bevel. Pivot the needle gently to create small pocket.
• Inject slowly and look for a bleb to form within the skin layer (should feel a slight resistance).
• If the skin doesn’t appear to rise immediately, the substance is going deeper than the intradermal layer. Stop the injection, remove needle and reposition.