SOP 7.9.1 - Subcutaneous Injection in Mice

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 mouse.
• 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 recommended but not mandatory for subcutaneous injections.
• Choose the appropriate administration route for the substance to be injected.

2. Materials:

• Sterile syringes
• Sterile needles (26-27 gauge)
• 70% alcohol
• Injectable solution

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.
• The most common injection site in the loose skin around the neck and shoulder area. Grasp the scruff and tent the skin upward. Depending on the volume to be administered, other SQ sites include the dorsolateral thorax and flank.
• Palpate toward the bottom of the tented skin to ensure interstitial space is accessible.
• Disinfect that injection site with 70% alcohol (if required).
• Insert the needle (bevel up) into the base of the tented region.
• Aspirate to ensure the placement of the needle is correct. Proper placement should yield negative pressure and no aspirate in the hub of the needle. If any fluids are seen; stop, reload with new syringe and needle, check injection site for trauma, reposition needle and attempt again.
• After ensuring proper placement, inject.
• If resistance is felt during the injection, stop and (slightly) reposition the needle.
• When injecting larger volumes or viscous substances, use the largest acceptable gauge needle for the animal.