How to administer dexamethasone to a rat? - briefly
Prepare a sterile dexamethasone solution at the required concentration and inject it intraperitoneally with a calibrated 27‑30 G needle, dosing according to body weight (e.g., 0.5 mg/kg). Restrain the rat gently, disinfect the injection site, and deliver the dose slowly to minimize tissue irritation.
How to administer dexamethasone to a rat? - in detail
Administering dexamethasone to a laboratory rat requires precise dosage calculation, sterile preparation, appropriate delivery route, and post‑administration monitoring.
Determine the dose based on body weight (mg kg⁻¹). Typical protocols use 0.5–2 mg kg⁻¹; adjust according to experimental design. Weigh the animal, calculate the required amount of dexamethasone, and dissolve the drug in a suitable vehicle (e.g., sterile saline, phosphate‑buffered saline, or a low‑volume dimethyl sulfoxide solution). Ensure the final concentration allows injection volumes not exceeding 10 mL kg⁻¹ for intraperitoneal (IP) or subcutaneous (SC) routes, or 1–2 mL for oral gavage.
Select the administration route:
- IP injection: rapid systemic absorption, suitable for acute studies.
- SC injection: slower release, useful for prolonged exposure.
- Oral gavage: mimics clinical oral dosing; requires a calibrated gavage needle.
Prepare equipment: sterile syringes (1 mL or 2.5 mL), appropriate gauge needles (27–30 G for IP/SC, 18–20 G for gavage), and a clean work surface. Disinfect the injection site with 70 % ethanol before each injection.
Procedure for IP injection:
- Restrain the rat gently using a tail‑hold or a restraining device.
- Locate the lower right quadrant of the abdomen, avoiding the midline and bladder.
- Insert the needle at a 30–45° angle, bevel up, until the tip enters the peritoneal cavity.
- Aspirate to confirm absence of blood or urine.
- Administer the calculated volume slowly.
- Withdraw the needle, apply gentle pressure to the site, and release the animal into its cage.
Procedure for SC injection:
- Restrain the rat as above.
- Pinch a fold of skin on the dorsal neck or flank.
- Insert the needle at a 45° angle, bevel up, into the subcutaneous space.
- Confirm free flow of solution, inject slowly, and release the skin fold.
Procedure for oral gavage:
- Secure the rat in a supine position with the head tilted upward.
- Insert the gavage needle gently along the esophagus, avoiding the trachea.
- Deliver the dose in one steady motion.
- Observe the animal for regurgitation; if observed, repeat the procedure with a fresh dose.
Post‑administration care includes monitoring for signs of distress, changes in behavior, weight loss, or injection site inflammation. Record observations at regular intervals (e.g., 15 min, 1 h, 24 h). Dispose of sharps in a designated container and decontaminate work surfaces with an appropriate disinfectant.