Where should you administer an intramuscular injection to a rat? - briefly
Inject into the lateral thigh muscle (quadriceps femoris) of the hind limb, using a 45‑degree angle and a needle length appropriate to the animal’s size. Avoid the femoral artery and vein by inserting laterally, midway between the hip and knee joints.
Where should you administer an intramuscular injection to a rat? - in detail
The preferred site for delivering an intramuscular dose in a laboratory rat is the lateral portion of the hindlimb, specifically the vastus lateralis muscle. This location provides ample muscle mass, minimal risk of nerve damage, and easy access when the animal is restrained.
To locate the muscle, place the rat in a supine or lateral position and identify the femur. The injection point lies midway between the greater trochanter and the knee joint, on the outer side of the thigh. Palpate the muscle bulk; the area feels firm and can accommodate volumes of 0.1 – 0.3 ml per 100 g body weight without causing excessive pressure.
Key procedural details:
- Restrain the animal using a snug but non‑restrictive holder or a brief period of anesthesia to reduce movement.
- Disinfect the skin with 70 % isopropanol and allow it to dry.
- Choose a sterile needle of appropriate gauge (25–27 G) and length (½ – 1 inch) based on the rat’s size.
- Insert the needle at a 90° angle to the skin, advancing until the hub contacts the muscle surface, then inject the solution steadily.
- Withdraw the needle swiftly, apply gentle pressure with sterile gauze, and observe the animal for any immediate adverse reaction.
Avoid alternative sites such as the gluteal region or the dorsal lumbar area, which present higher chances of hitting bone, major blood vessels, or the sciatic nerve. Proper placement in the lateral thigh muscle ensures reliable absorption and minimizes tissue trauma.