How should analgin be given to a rat? - briefly
Administer analgin to a rat by intraperitoneal injection at a dose of approximately 200 mg per kilogram of body weight, dissolved in sterile saline and delivered in a volume not exceeding 10 ml/kg. Observe the animal for analgesic effect and any adverse reactions following injection.
How should analgin be given to a rat? - in detail
Analgin (metamizole sodium) must be prepared in sterile physiological saline at a concentration that allows accurate dosing. A common solution is 10 mg ml‑1; adjust concentration if a different volume per kilogram is required.
The dose for a typical adult rat (200–250 g) ranges from 50 to 100 mg kg‑1 body weight. Calculate the exact amount of drug, then withdraw the corresponding volume from the prepared solution. For a 250‑g animal receiving 75 mg kg‑1, the required dose is 18.75 mg, which equals 1.9 ml of a 10 mg ml‑1 solution.
Select the route that provides rapid systemic absorption while minimizing stress:
- Intraperitoneal injection – most widely used for acute analgesia. Use a 27‑ to 30‑gauge needle, insert at a shallow angle into the lower right quadrant of the abdomen, avoid puncturing intestines. Inject the calculated volume slowly (≤0.5 ml min‑1).
- Subcutaneous injection – suitable for prolonged effect. Inject into the scruff of the neck or the dorsal flank using a 25‑ to 27‑gauge needle. Distribute the volume over a small area to prevent tissue irritation.
- Oral gavage – applicable when repeated dosing is needed. Use a flexible gavage tube of appropriate size, deliver the solution directly to the stomach, and verify correct placement before administration.
Before injection, restrain the rat gently with a calibrated restrainer or by manual handling, ensuring the animal is calm to reduce the risk of accidental injury. Apply aseptic technique: disinfect the injection site with 70 % ethanol, allow it to dry, and use a sterile syringe.
After administration, observe the animal for at least 30 minutes. Monitor for signs of analgesia (reduced withdrawal reflexes) and adverse reactions (hypotension, respiratory depression, skin irritation at the injection site). Record the time of dosing, volume administered, and any observations in the experimental log.
If multiple doses are required, maintain a minimum interval of 4–6 hours between injections to avoid cumulative toxicity. Adjust the dose based on the animal’s weight and response, never exceeding 100 mg kg‑1 per administration.