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Calculate the absolute bioavailability F of an extravascular (typically oral) dose: F = (AUC_po · Dose_iv) / (AUC_iv · Dose_po), where AUC_po and AUC_iv are the areas under the concentration-time curve after oral and IV dosing, and the doses correct for any difference in amount administered. F is dimensionless and lies in [0, 1]; IV bioavailability is by definition 1, while oral F < 1 reflects incomplete absorption and/or first-pass metabolism. AUC can be in any consistent unit (e.g. mg·h/L) since it cancels out of the ratio. Valid only for linear pharmacokinetics, the same drug molecule, and doses within the linear range. Not medical advice.
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Tool usage guide
Calculate absolute bioavailability (F) for an oral or other extravascular dose using dose-corrected oral and IV AUC values: F = (AUC_po × Dose_iv) / (AUC_iv × Dose_po). The result is dimensionless and shown as a fraction and percentage.
Background
A study reports an oral AUC of 100 mg·h/L and an IV AUC of 120 mg·h/L after equal 200 mg doses.
Problem
Calculate absolute bioavailability when the oral and IV doses are the same.
How to use
Enter aucPo = 100, aucIv = 120, dosePo = 200, and doseIv = 200.
Decimal places: 4Outcome
The calculator returns F = 0.8333, or 83.33%. With equal doses, this equals 100 ÷ 120.
Background
An oral study uses a 300 mg dose and produces an AUC of 90 mg·h/L. The IV reference uses 100 mg and produces an AUC of 150 mg·h/L.
Problem
Account for the unequal doses when estimating absolute bioavailability.
How to use
Enter aucPo = 90, aucIv = 150, dosePo = 300, and doseIv = 100.
Decimal places: 4It represents absolute bioavailability, or the fraction of an extravascular dose reaching systemic circulation relative to an IV dose.
You need the oral AUC, IV AUC, oral dose, and IV dose. All four values must be positive.
No. The formula adjusts for different doses. If the doses are equal, F simplifies to AUC_po divided by AUC_iv.
Use any consistent AUC unit for both measurements, such as mg·h/L. The AUC units cancel in the ratio.
It is intended for the same drug molecule, linear pharmacokinetics, and doses within the linear range. It is not medical advice.
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Outcome
The dose-corrected result is F = 0.2, or 20%.