PK Log Concentration Replicate Delta Tool

Description

For positive first and second concentrations return logDifference=ln(second)-ln(first), geometricMean=exp((ln(first)+ln(second))/2), and ratio=second/first.

Pharmacokinetic research describes concentration over time using measurement units and an explicit model. Concentration-time area, its time-weighted moment, inverse-time rate constants, clearance, and volume are related but distinct quantities. A conversion or local model term does not estimate every parameter or validate a complete study.

For positive first and second concentrations return logDifference=ln(second)-ln(first), geometricMean=exp((ln(first)+ln(second))/2), and ratio=second/first.

When to use this tool

Use PK Log Concentration Replicate Delta when you need this concentration-time conversion, sampling check, local integral panel, or explicitly supplied kinetic-model term.

How to use the tool and how it works

Enter first, second. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read logDifference, geometricMean, ratio. Use the output convention below.

For positive first and second concentrations return logDifference=ln(second)-ln(first), geometricMean=exp((ln(first)+ln(second))/2), and ratio=second/first.^[1]

Input field	Meaning and units	Accepted input
first	First	Required. Finite number; strictly above 0.
second	Second	Required. Finite number; strictly above 0.

Output field	Interpretation	Returned shape
logDifference	Log Difference	Required. Finite number.
geometricMean	Geometric Mean	Required. Finite number.
ratio	Ratio in the direction and unit convention stated in the formula.	Required. Finite number.

json

{
  "input": {
    "first": 2,
    "second": 8
  },
  "output": {
    "logDifference": 1.3862943611198904,
    "geometricMean": 4,
    "ratio": 4
  }
}

Limitations and assumptions

Concentrations need the same unit and logDifference is a dimensionless natural log ratio. Two values alone do not establish replicate precision, bioequivalence, or an acceptable assay.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Signed zero is exported as zero.

Alternative or Complementary methods

Use a complete study analysis when a local panel, transformation, or model factor is insufficient. Check sampling times, censoring, assay support, unit conventions, and the validity of the assumed kinetic regime.

References

Calculation and input contract: pharmacokinetics/pk-log-concentration-replicate-delta — tool.io

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