Where should an antibiotic be injected into a rat? - briefly
Administer the antibiotic intraperitoneally with a sterile 25‑27 G needle. A subcutaneous injection over the dorsal flank provides an alternative route for systemic absorption.
Where should an antibiotic be injected into a rat? - in detail
The most reliable locations for delivering an antibiotic to a laboratory rat are intraperitoneal, subcutaneous, intramuscular, and intravenous sites. Selection depends on drug properties, desired absorption rate, and experimental requirements.
Intraperitoneal injection provides rapid systemic distribution. The needle is introduced at a 30‑45° angle into the lower right quadrant of the abdomen, avoiding the liver and bladder. A 25‑27 G needle is appropriate for volumes up to 2 mL. Ensure the needle tip is fully within the peritoneal cavity by observing a slight resistance release before injecting.
Subcutaneous injection yields slower absorption, suitable for prolonged release. The injection site is the dorsal scruff region, where the skin can be gently lifted to form a tent. Use a 27‑30 G needle, inserting at a shallow 10‑15° angle. Volumes should not exceed 0.5 mL to prevent tissue distortion.
Intramuscular injection targets the hind‑limb thigh muscle (vastus lateralis). Locate the muscle by palpating the lateral aspect of the femur. Insert a 25‑27 G needle perpendicular to the skin, advancing 5‑7 mm. Recommended volume is 0.1‑0.2 mL per site; larger doses can be split across both thighs.
Intravenous administration affords immediate bioavailability. The lateral tail vein is the preferred access point. Warm the tail with a heat lamp for 1‑2 minutes to dilate the vessel. Use a 30‑32 G catheter or needle, inserting bevel up at a shallow angle. Flush with sterile saline before and after drug delivery. Maximum volume is 0.2 mL to avoid circulatory overload.
General procedural guidelines:
- Prepare the antibiotic in sterile, isotonic solution; filter if particulate matter is present.
- Verify dosage based on body weight (typically mg kg⁻¹).
- Disinfect the injection site with 70 % ethanol; allow to dry.
- Use aseptic technique throughout; replace needles after each animal.
- Monitor the rat for adverse reactions during and after injection; observe for signs of distress, swelling, or hemorrhage.
Adhering to these site‑specific techniques ensures accurate dosing, minimizes tissue trauma, and supports reproducible experimental outcomes.