Calculating Human Equivalent Dosages from Animal Studies

𝗖𝗮𝗹𝗰𝘂𝗹𝗮𝘁𝗶𝗻𝗴 𝗛𝘂𝗺𝗮𝗻 𝗘𝗾𝘂𝗶𝘃𝗮𝗹𝗲𝗻𝘁 𝗗𝗼𝘀𝗮𝗴𝗲𝘀 𝗳𝗿𝗼𝗺 𝗔𝗻𝗶𝗺𝗮𝗹 𝗦𝘁𝘂𝗱𝗶𝗲𝘀
A common mistake in translating animal study dosages to humans is using body weight scaling (mg/kg). This ignores critical differences in metabolism and physiology across species. Instead, allometric scaling—which accounts for body surface area and species-specific metabolic rates—should be used.

Nair and Jacob (2016) have previously calculated conversion factors (Km ratios) for the most commonly used animals in research. The formula for Human Equivalent Dose (HED) is:

HED (mg/kg) = Animal dose (mg/kg) × Kₘ ratio

𝗘𝘅𝗮𝗺𝗽𝗹𝗲 𝗖𝗮𝗹𝗰𝘂𝗹𝗮𝘁𝗶𝗼𝗻
If a 200g mouse is given 10 mg of a compound:

HED (mg/kg) = (10 mg/ 0.2 kg) × 0.081 = 4.05 mg/kg for humans.

𝗞𝗲𝘆 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆
Body weight alone is misleading – Smaller animals have faster metabolisms, so humans need proportionally lower doses.

𝗥𝗲𝗳𝗲𝗿𝗲𝗻𝗰𝗲:
Nair, A. B., & Jacob, S. (2016). A simple practice guide for dose conversion between animals and humans. Journal of Basic and Clinical Pharmacy, 7(2), 27–31.