Where to inject ceftriaxone into a rat? - briefly
The standard site for ceftriaxone administration in laboratory rats is the intraperitoneal cavity, using a sterile 25‑27 G needle. An alternative is a tail‑vein injection for precise systemic delivery.
Where to inject ceftriaxone into a rat? - in detail
Ceftriaxone can be administered to laboratory rats through several routes, each with specific anatomical sites and technique considerations.
Intraperitoneal injection
- Site: lower right quadrant of the abdomen, avoiding the cecum and liver.
- Needle: 25‑27 G, ½‑inch.
- Volume: ≤10 mL kg⁻¹ of body weight.
- Procedure: Restrain the animal, lift the abdominal wall, insert the needle at a 30‑45° angle, aspirate to confirm entry into the peritoneal cavity, then deliver the drug.
Subcutaneous injection
- Site: loose skin over the dorsal thoracic region or the scruff of the neck.
- Needle: 27‑30 G, ½‑inch.
- Volume: ≤2 mL kg⁻¹.
- Procedure: Pinch the skin fold, insert the needle bevel up at a shallow angle, ensure no resistance, and inject.
Intravenous injection (tail vein)
- Site: lateral tail vein, typically 2–3 cm distal to the base.
- Needle: 30‑32 G, ½‑inch.
- Volume: ≤0.5 mL kg⁻¹.
- Procedure: Warm the tail to dilate vessels, secure the rat, insert the needle bevel up at a 10‑15° angle, confirm blood return, then administer the solution slowly.
Intramuscular injection
- Site: quadriceps femoris or gastrocnemius of the hind limb.
- Needle: 25‑27 G, ½‑inch.
- Volume: ≤0.1 mL g⁻¹.
- Procedure: Extend the limb, locate the muscle bulk, insert the needle perpendicular to the skin, aspirate, and inject.
Retro‑orbital injection (only for anesthetized animals)
- Site: retro‑orbital sinus.
- Needle: 27‑30 G, ½‑inch.
- Volume: ≤0.1 mL kg⁻¹.
- Procedure: Anesthetize fully, use a blunt‑ended cannula, penetrate the medial canthus, and deliver the dose.
General preparation guidelines
- Dissolve ceftriaxone in sterile saline; pH should be 7.0–7.4.
- Filter the solution through a 0.22 µm membrane.
- Use aseptic technique, change needles between animals, and dispose of sharps according to institutional biosafety protocols.
Selection of route depends on experimental objectives, required absorption speed, and animal welfare considerations. Intraperitoneal and subcutaneous routes are common for routine dosing, while intravenous administration provides rapid systemic exposure.