Which precaution is most appropriate to reduce risk during IP injections in mice?

• A. Use a large-gauge needle and inject into the hind limb
• B. Use a small-gauge needle and insert into the caudal abdominal quadrant
• C. Insert into the chest cavity to speed absorption
• D. Administer via subcutaneous route

Answer: (B)

When performing intraperitoneal injections in mice, the goal is to deliver into the peritoneal space while minimizing injury to internal organs. The safest approach uses a fine, small-gauge needle and targets a position in the caudal abdominal quadrant. This area is away from major organs like the liver, spleen, and intestines, reducing the chance of puncturing an organ and causing peritoneal damage. A smaller needle size also lessens tissue trauma if a misdirected insertion occurs, helping preserve the animal’s wellbeing.

Avoid inserting into the chest cavity, which risks lung or heart injury, and avoid a subcutaneous route, which does not place the substance into the peritoneal cavity. A larger-gauge needle increases tissue damage and the likelihood of inadvertently injuring organs. The hind limb site is not appropriate for intraperitoneal administration and can cause local tissue damage.