Safe and effective drug dosing is necessary, regardless of its purpose of administration. Allometric scaling is an empirical approach where the exchange of drug dose is based on normalization of dose to body surface area. This approach assumes that there are some unique characteristics on anatomical, physiological, and biochemical process among species, and the possible difference in pharmacokinetics/physiological time is accounted by allometric scaling. This method is frequently used in research for experimental purpose to predict an approximate dose on the basis of data existing in other species. The US Food and Drug Administration's current guidance is based on dose by factor approach where the NOAEL of drug is scaled by making use of allometry to derive the maximum recommended starting dose (MRSD) for clinical studies.
Usually the correction factor (Km) is used to estimate the animal equivalent dose (AED) for different animal species. Km is estimated by dividing the average body weight (kg) of species to its body surface area (m2). For example, the average human body weight is 60 kg, and the body surface area is 1.62 m2. Therefore, the Km factor for human is calculated by dividing 60 by 1.62, which is 37. As the Km factor for each species is constant, the Km ratio is used to simplify calculations. AED can be estimated as: AED1 (mg/kg) = AED2 (mg/kg) × Km ratio (Km2/Km1) Eq.1; or AED1 (mg/kg) = AED2 (mg/kg) × Weight2 (kg) × BSA ratio (BSA1/BSA2) Eq.2.
|Species||Reference body weight (kg)||To convert dose in mg/kg to dose in mg/m2, divide by km||To convert human dose in mg/kg to AED in mg/kg，either|
|Multiply human dose by||Divide human dose by|