How do you calculate the azithromycin dose for a rat? - briefly
Calculate the required amount by multiplying the animal’s body weight (kg) by the target dosage (mg · kg⁻¹), then convert the product to the appropriate volume using the drug’s concentration. For rats, a common regimen is 10 mg · kg⁻¹ administered orally, so a 0.250‑kg rat needs 2.5 mg, which corresponds to 0.25 ml of a 10 mg/ml azithromycin solution.
How do you calculate the azithromycin dose for a rat? - in detail
To determine an appropriate azithromycin amount for a laboratory rat, follow a systematic conversion from the established human dosage.
First, identify the reference human dose expressed in milligrams per kilogram (mg · kg⁻¹). Common therapeutic regimens cite 10 mg · kg⁻¹ per day for adults.
Second, adjust for interspecies differences using allometric scaling based on body‑surface‑area constants (Km values). The human Km is 37, the rat Km is 6. The conversion factor is therefore 37 ÷ 6 ≈ 6.2.
Apply the formula:
Rat dose (mg · kg⁻¹) = Human dose (mg · kg⁻¹) × 6.2
For a 250‑g rat (0.25 kg) and a human dose of 10 mg · kg⁻¹:
Rat dose = 10 × 6.2 ≈ 62 mg · kg⁻¹
Total amount = 62 mg · kg⁻¹ × 0.25 kg ≈ 15.5 mg
Third, translate the calculated amount into a practical administration volume. If the azithromycin solution contains 200 mg · ml⁻¹, the required volume is:
Volume = 15.5 mg ÷ 200 mg · ml⁻¹ ≈ 0.078 ml (78 µl)
Select the route of delivery—oral gavage, intraperitoneal, or subcutaneous injection—according to experimental requirements. Ensure the final volume does not exceed 10 ml · kg⁻¹ for oral gavage or 5 ml · kg⁻¹ for parenteral routes to avoid distress.
Finally, verify that the administered dose remains within established safety margins for rodents, typically not exceeding 100 mg · kg⁻¹ per day. Adjust the schedule if repeated dosing is planned.