Modifications of the Method for Calculating Absolute Drug Bioavailability

Area of Science:

• Pharmacokinetics
• Drug Development
• Bioavailability Studies

Background:

• Absolute bioavailability (F) is crucial for drug efficacy.
• Standard calculation relies on Area Under the Curve (AUC) from extravascular and intravenous administration.
• The distribution phase after IV injection can lead to inaccurate AUC measurements.

Purpose of the Study:

• To analyze the limitations of the current absolute bioavailability calculation method.
• To propose a modification for improved accuracy in bioavailability assessment.
• To address the underestimation of drug bioavailability.

Main Methods:

• Literature search for absolute bioavailability studies (1983-2014).
• Calculation of plasma drug concentrations during the distribution phase.
• Utilized plasma drug concentration-time data from the elimination phase for calculations.

Main Results:

• AUC values based on distribution equilibrium were 75%±11% of measured values.
• Calculated absolute bioavailability was 76%±12% of actual bioavailability.
• The standard method shows a consistent underestimation of bioavailability.

Conclusions:

• The existing method for absolute bioavailability calculation underestimates drug levels.
• A modification is necessary for more accurate bioavailability data.
• Accurate bioavailability assessment is vital for effective drug development and dosing.