How to administer medicine to a rat? - briefly
Use a calibrated oral gavage needle or a sterile syringe with a 27‑30 G needle to deliver the dose directly into the mouth while gently restraining the rat and angling the head upward to avoid aspiration. For subcutaneous injection, lift a dorsal skin fold and inject the calculated volume into the space without penetrating muscle.
How to administer medicine to a rat? - in detail
Administering medication to a laboratory rat requires precise dosing, appropriate route selection, and careful handling to ensure reproducibility and animal welfare.
First, determine the exact dose. Multiply the animal’s body weight (in grams) by the prescribed milligram‑per‑kilogram dosage, then convert to the volume needed based on the drug’s concentration. Prepare the solution under sterile conditions, using a calibrated syringe. Warm the preparation to room temperature to avoid vasoconstriction or gastrointestinal irritation.
Restraint must be firm yet gentle. Hold the rat by the scruff of the neck with one hand while supporting the body with the other, or place the animal in a clear plastic restrainer. Avoid excessive pressure that could cause injury or stress‑induced physiological changes.
Common administration routes and their technical details:
- Oral gavage – Use a flexible, curved feeding needle (20‑22 G). Insert the needle along the midline of the tongue, advance until the base of the jaw is reached, then deliver the calculated volume (max 0.2 mL per 100 g body weight). Verify correct placement by observing the absence of resistance and the animal’s swallowing reflex.
- Subcutaneous injection – Choose a short‑bevel needle (25‑27 G). Pinch a loose area of skin on the dorsal flank, insert the needle at a shallow angle (30‑45°), and inject the solution (max 0.5 mL per 100 g). Release the skin after injection to prevent leakage.
- Intraperitoneal injection – Employ a 25‑G needle. Locate the lower right quadrant of the abdomen, insert the needle at a 30° angle to avoid organ puncture, and deliver the dose (max 1 mL per 100 g). Observe for any signs of peritonitis post‑procedure.
- Intravenous injection – Access the lateral tail vein using a 30‑G needle. Dilate the vein with warm water, insert the needle bevel up, and administer the drug slowly (max 0.1 mL per 100 g). Confirm venous entry by the absence of resistance and a flash of blood.
After delivery, place the rat in a clean cage with easy access to food and water. Monitor for at least 30 minutes, noting respiratory rate, locomotor activity, and any signs of distress or adverse reactions. Record the time of administration, dose, route, and observed effects in the animal’s log.
Adhering to these steps ensures accurate dosing, minimizes procedural variability, and upholds ethical standards in rodent pharmacological studies.