Drug Clearance from Dose and AUC: Clinical Guide

Overview

Calculates apparent systemic clearance from dose, bioavailability and area under the concentration–time curve.

Clinical Significance

The equation estimates systemic clearance after a dose when exposure is adequately characterised. It assumes compatible dose and AUC units and usually linear pharmacokinetics.

When to Use

• Estimate clearance from a complete concentration–time exposure estimate.
• Use bioavailability of 1 for an intravenous dose.
• Use the same dosing interval and AUC definition.

How It Is Calculated

• Clearance = dose × bioavailability ÷ AUC.
• The calculator validates the required inputs before applying the equation and rounds only the displayed result.

Interpretation

• The equation estimates systemic clearance after a dose when exposure is adequately characterised. It assumes compatible dose and AUC units and usually linear pharmacokinetics.
• Review the component values and assumptions as well as the final result.

Worked Example

Enter clinically plausible values in the stated units. MedicalC applies: Clearance = dose × bioavailability ÷ AUC. Review the displayed result against the source data and the relevant clinical pathway.

Patient Considerations

• Confirm that the patient and clinical setting match the population or physiologic assumptions behind the equation.
• Consider whether treatment, organ function, pregnancy, body composition, sampling conditions or acute illness materially alter interpretation.
• Use serial calculations only when methods and units remain comparable.

Limitations

• Sparse or inaccurate AUC estimates produce inaccurate clearance.
• The relationship may not be linear at all doses.
• Changing physiology or time-dependent clearance limits extrapolation.

Clinical Pearls

• For oral dosing the result is CL/F unless true bioavailability is known.
• Confirm whether AUC is AUC0–∞ or interval AUC.
• Match hour-based AUC with L/hour clearance.

Common Mistakes

• Assuming oral bioavailability is 1.
• Using an AUC from a different dose interval.
• Mixing mass units.

Evidence Base

The implementation uses the published or established relationship: Clearance = dose × bioavailability ÷ AUC. The cited source should be reviewed alongside current specialty guidance before clinical deployment.

References

1. Rowland M, Tozer TN. Clinical Pharmacokinetics and Pharmacodynamics: Concepts and Applications. — Primary publication, authoritative guideline or recognised clinical source supporting the calculation.