Bioavailability Calculator

Absolute bioavailability is the fraction of an orally administered drug that reaches systemic circulation unchanged, expressed as a percentage. It compares the AUC after oral administration to the AUC after intravenous administration, adjusted for dose differences.

Bioavailability (F%) is calculated using the formula: F = (AUC_oral × Dose_IV) / (AUC_IV × Dose_oral) × 100. This accounts for differences in both systemic exposure (AUC) and administered doses between routes.

100% bioavailability means that the entire administered oral dose reaches systemic circulation. Only intravenous administration typically achieves 100% bioavailability, while oral bioavailability is usually lower due to first-pass metabolism and incomplete absorption.

Bioavailability is crucial for determining appropriate dosing, comparing different formulations, and understanding how much active drug reaches the target site. It helps predict therapeutic efficacy and guides dosage adjustments between different routes of administration.

Oral bioavailability is affected by drug absorption in the gastrointestinal tract, first-pass metabolism in the liver, drug solubility, formulation properties, and individual patient factors like gastric pH and intestinal transit time.

Absolute bioavailability compares oral administration to intravenous administration (the gold standard). Relative bioavailability compares two different oral formulations or routes of the same drug, typically expressed as a ratio or percentage.

AUC units must be consistent between oral and intravenous measurements for accurate calculation. The calculator handles unit conversions automatically, but using the same units for both measurements ensures the most reliable results.