Absolute bioavailability

Absolute Bioavailability is a concept in pharmacokinetics that refers to the amount of a drug that reaches the systemic circulation after administration, compared to the amount that would reach the circulation if the drug were given intravenously. It is a measure of the efficiency of drug absorption and first-pass metabolism.

Definition

The absolute bioavailability of a drug is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation. It is typically expressed as a percentage. The absolute bioavailability is calculated by comparing the area under the plasma concentration-time curve (AUC) after non-intravenous administration, to the AUC after intravenous administration.

Factors Influencing Absolute Bioavailability

Several factors can influence the absolute bioavailability of a drug. These include the drug formulation, the route of administration, the rate and extent of drug absorption, and the extent of first-pass metabolism in the liver and gut wall.

Importance in Drug Development

Understanding the absolute bioavailability of a drug is crucial in drug development. It helps in determining the correct dosage and route of administration for a new drug. It also aids in predicting the drug's pharmacodynamics and pharmacokinetics.

See Also

• Bioavailability
• Pharmacokinetics
• Drug absorption
• First-pass metabolism