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Calcimator

Toxicology Dose Back-Calculator

Back-calculate an ingested dose from blood concentration using volume of distribution and elimination kinetics. Estimate peak concentration and elimination time.

Inputs

mg/L
lb
L/kg
/hr

Results

Estimated Ingested Dose

24.5 mg

Time to Eliminate

39.1 hrs

Est. Peak Concentration0.65 mg/L
Half-Life6.9 hrs
How to Use This Calculator
  1. Enter Blood Concentration, Body Weight, and Volume of Distribution (Vd).
  2. Set Elimination Rate (ke).
  3. Review Estimated Ingested Dose (mg) and Time to Eliminate (hrs).
  4. Use Est. Peak Concentration (mg/L) and Half-Life (hrs) to inform your decision.
  5. Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Blood Concentration

Blood ConcentrationEstimated Ingested DoseTime to Eliminate
502,450 mg85.2 hrs
1758,575 mg97.7 hrs
32515,925 mg103.9 hrs
45022,050 mg107.1 hrs

What each input means

Blood Concentration
Measured blood/plasma drug concentration at time of sampling.
Body Weight
Deceased's body weight in kilograms.
Volume of Distribution (Vd)
Drug-specific Vd (e.g., ethanol 0.7, diazepam 1.1, fentanyl 4.0).
Elimination Rate (ke)
First-order elimination rate constant (ke = 0.693 / half-life).

What each result means

Estimated Ingested Dose
Minimum dose that could produce the measured concentration.
Est. Peak Concentration
Estimated peak blood level (approximate).
Time to Eliminate
Hours until blood level drops below 0.01 mg/L.
Half-Life
Drug elimination half-life from the given rate constant.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Blood Concentration = 0.5, Body Weight = 70, Volume of Distribution (Vd) = 0.7, Elimination Rate (ke) = 0.1 = 4 input(s) provided
  2. Calculate Estimated Ingested Dose
    Estimated Ingested Dose
    24.5 = 24.5
  3. Calculate Time to Eliminate
    Time to Eliminate
    39.1 = 39.1
  4. Calculate Est. Peak Concentration
    Est. Peak Concentration
    0.65 = 0.65

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