How should dexamethasone be administered to rats? - briefly
Administer dexamethasone to rats by intraperitoneal injection at 0.5–1 mg kg⁻¹ once daily, using a sterile saline solution. Prepare the drug in a sterile container and inject with a 27‑gauge needle to reduce tissue damage.
How should dexamethasone be administered to rats? - in detail
Administering dexamethasone to laboratory rats requires precise preparation, selection of an appropriate route, and strict adherence to dosing guidelines to achieve reproducible pharmacological effects while minimizing stress and toxicity.
First, dissolve the compound in a suitable vehicle. Common solvents include sterile saline, phosphate‑buffered saline, or a mixture of saline with a small proportion of dimethyl sulfoxide (≤5 %). Ensure the solution is filtered through a 0.22 µm membrane to remove particulates and maintain sterility. Prepare the dose immediately before use to avoid degradation; dexamethasone is stable for several hours at room temperature but should be stored at 4 °C if a longer interval is required.
Select the administration route based on experimental objectives:
- Intraperitoneal (IP) injection: Provides rapid systemic absorption. Use a 27‑30 G needle, inject into the lower right quadrant of the abdomen, avoiding the cecum. Typical volume does not exceed 1 mL per 100 g body weight.
- Subcutaneous (SC) injection: Suitable for slower release. Inject into the dorsal flank with a 25‑27 G needle. Volume limit is 0.5 mL per 100 g.
- Oral gavage: Enables chronic dosing. Use a flexible gavage needle (1–2 mm diameter) to deliver the solution directly to the stomach. Volume should not exceed 2 mL per kg.
- Intravenous (IV) injection: Reserved for acute studies requiring immediate plasma peaks. Perform via the tail vein with a 30‑G needle; keep volume ≤0.2 mL per 100 g.
Determine dosage according to the study design and literature precedent. Common regimens range from 0.1 to 5 mg kg⁻¹ body weight per day. For anti‑inflammatory models, 0.5 mg kg⁻¹ administered once daily is frequently employed. Adjust the dose based on strain, age, and sex, as metabolic rates differ among these variables.
Administration protocol:
- Weigh each rat individually; record body weight to the nearest 0.1 g.
- Calculate the required drug amount using the formula:
[ \text{Dose (mg)} = \text{Weight (kg)} \times \text{Desired dose (mg kg⁻¹)} ] - Transfer the calculated volume of prepared solution into a sterile syringe.
- Restrain the animal gently but securely; use a rodent restrainer or manual hold to prevent movement.
- Perform the injection according to the chosen route, ensuring the needle penetrates the appropriate tissue plane.
- Observe the injection site for bleeding or swelling; apply gentle pressure if needed.
- Return the rat to its cage; monitor for at least 30 minutes for signs of distress, respiratory difficulty, or abnormal behavior.
Record all variables—time of administration, exact dose, vehicle composition, injection site, and any adverse observations—in a laboratory notebook. Maintain a consistent schedule (e.g., same time each day) to reduce circadian influences on drug metabolism.
Finally, comply with institutional animal care guidelines: use aseptic technique, provide analgesia if required, and ensure that personnel are trained in rodent handling and injection procedures. Regularly review the protocol with the veterinary staff to confirm that dosing remains within safe limits for the specific strain and experimental duration.