Allometric Scaling Dose

Scale total dose with a supplied mass exponent and recover mass-normalized target dose; species kinetics and human dosing suitability are not inferred.

Description

Scale a total dose by a supplied body-mass exponent and recover the target dose in mg/kg.

Allometric scaling describes a quantity as a power of body mass. Scaling a total dose and scaling a dose per kilogram are different operations: dividing the scaled total by target mass changes the effective exponent. Species extrapolation additionally requires biological and assessment evidence.^[1]

This calculator multiplies the source mg/kg dose by source kg to get total mg, scales that total by the target-to-source mass ratio raised to your exponent, then divides by target kg. It supplies no default species conversion or clinical starting-dose decision.

When to use Allometric Scaling Dose

Use it to reproduce an explicitly chosen mass-scaling scenario or compare the arithmetic for different total-dose exponents.

How to use Allometric Scaling Dose and understand its results

Enter positive sourceDoseMgPerKg, sourceMassKg, and targetMassKg in the stated units.
Enter totalDoseMassExponent between zero and one inclusive, chosen for the intended scaling model, then run the calculation.
Read targetTotalDoseMg and targetDoseMgPerKg together and retain the exponent and biological rationale with the scenario.

target total = source dose × source mass × (target mass/source mass)^b; target mg/kg = source mg/kg × (target mass/source mass)^(b − 1)

b applies to total dose, not directly to dose per kilogram.

json

{
  "input": {
    "sourceDoseMgPerKg": 10,
    "sourceMassKg": 1,
    "targetMassKg": 16,
    "totalDoseMassExponent": 0.75
  },
  "output": {
    "targetDoseMgPerKg": 5,
    "targetTotalDoseMg": 80
  }
}

Exponent one preserves the mg/kg dose; exponent zero preserves total mg. Equal masses preserve both measures. Zero or negative source dose or mass, and exponents outside [0, 1], are rejected.

Limitations and assumptions

Body mass and an exponent do not establish comparable kinetics, bioavailability, target-organ sensitivity, or safety across species. No safety factor or endpoint adjustment is included.

The tool does not implement a complete human-equivalent-dose or maximum-starting-dose assessment. The synthetic example is arithmetic, not a recommended dose.

Alternative or Complementary methods

Use a mechanism-specific clearance calculation when suitable input evidence is available. A separately justified point-of-departure and exposure comparison can show a margin after the dose bases have been reconciled.

References

Estimating the Maximum Safe Starting Dose in Initial Clinical Trials for Therapeutics in Adult Healthy Volunteers (2005) — U.S. Food and Drug Administration

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