Use this pharmacokinetic calculation when dose, exposure, concentration, time, and route use compatible units and refer to the same analyte and study period.

Starting concentration

Concentration at the start of the interval; must not be negative.

Ending concentration

Concentration at the end of the interval; must not be negative.

Start time

Time at the start of the interval.

End time

Time at the end of the interval; must be later than the start time.

The implementation follows this calculation rule: Compute the trapezoidal area under a concentration-time segment as the average of the two concentrations multiplied by the elapsed time interval.

Area under curve

Trapezoidal area under the concentration-time segment.

AUC segments, clearance, bioavailability, bioequivalence ratios, and concentration–response parameters depend on sampling design and model assumptions. Sparse sampling, extrapolation, nonlinear kinetics, active metabolites, and unaligned doses can invalidate a comparison. Ratios and percentages become unstable when their denominator is small, uncertain, or defined differently between samples.

Inspect the concentration–time data and calculate uncertainty with an appropriate pharmacokinetic model. Peak concentration, time to peak, terminal half-life, and dose-normalized exposure often provide complementary information.

• Bioequivalence Ratio

  Express bioequivalence as the test product area under the curve as a percentage of the reference product area under the curve.

• Steady-State Concentration

  Predict the average plasma concentration at steady state as the infusion rate times bioavailability divided by clearance.

• EC50 From Hill

  Estimate the half-maximal effective concentration by inverting the Hill equation.