How do you calculate the doxycycline dose for a rat?

How do you calculate the doxycycline dose for a rat? - briefly

Multiply the target milligrams per kilogram by the rat’s weight in kilograms to obtain the total amount needed; for example, a 0.25 kg rat receiving 5 mg/kg requires 1.25 mg of doxycycline. Adjust the concentration of the administered solution accordingly to deliver this exact dose.

How do you calculate the doxycycline dose for a rat? - in detail

Determining the appropriate amount of doxycycline for a laboratory rat requires conversion of the target dose (expressed in mg per kilogram of body weight) into a measurable volume of the preparation being administered.

1. Identify the intended dose.
   Typical therapeutic regimens for rodents range from 5 mg kg⁻¹ to 20 mg kg⁻¹ per day, depending on the experimental model and route of administration. Choose the specific value required for the study.

2. Measure the animal’s weight.
   Weigh the rat on a calibrated balance; record the mass in kilograms (e.g., a 250‑g rat = 0.250 kg).

3. Calculate the absolute quantity of drug.
   [ \text{Dose (mg)} = \text{Target dose (mg kg⁻¹)} \times \text{Weight (kg)} ]
   Example: 10 mg kg⁻¹ × 0.250 kg = 2.5 mg doxycycline.

4. Select the formulation.
   Doxycycline is commonly supplied as a powder for reconstitution (e.g., 100 mg mL⁻¹) or as a tablet (e.g., 100 mg per tablet). Use the concentration of the solution you will administer.

5. Convert the required mass to volume.
   [ \text{Volume (mL)} = \frac{\text{Dose (mg)}}{\text{Solution concentration (mg mL⁻¹)}} ]
   Example: 2.5 mg ÷ 100 mg mL⁻¹ = 0.025 mL (25 µL).

6. Adjust for administration route.

   • Oral gavage: dissolve the calculated volume in a suitable vehicle (e.g., sterile water) and deliver the exact amount using a calibrated gavage needle.
   • Intraperitoneal injection: ensure the final concentration does not exceed 10 mg mL⁻¹ to avoid irritation; dilute if necessary.
   • Drinking water: calculate daily water intake (≈30 mL kg⁻¹ for rats) and add doxycycline to achieve the desired mg kg⁻¹ dose over 24 h.

7. Verify stability.
   Doxycycline degrades in light and at high pH; prepare solutions fresh or store protected from light at 4 °C for no longer than 24 h.

8. Document the calculation.
   Record weight, target dose, solution concentration, and administered volume for each animal to ensure reproducibility and compliance with ethical guidelines.

By following these steps, the exact amount of doxycycline required for a rat of any given weight can be accurately determined and administered.