Clinical Pharmacokinetics: Bioavailability and Oral Dosing

BIOPHARMACEUTICS

is a field of study that focuses on understanding how different factors affect the nature and strength of a drug's effect

BIOAVAILABILITY

refers to the rate and extent at which a drug reaches the bloodstream and becomes available for its intended action in the body

ABSOLUTE BIOAVAILABILITY

bioavailability (F) is often determined by comparing the area under the curve of a drug when taken orally with the AUC when the same dose is administered intravenously

POOR BIOAVAILABILITY

when a drug has a _, it means that it is not fully absorbed into the bloodstream or is eliminated by the liver before it reaches systemic circulation (lower than expected drug concentrations in the blood)

RELATIVE BIOAVAILABILITY

• differences in bioavailability can be observed between two products (A and B) that contain the same active drug
• these differences occur because the formulations of the products are different
• different plasma concentrations of the drug (varying absorption characteristics)

AREA UNDER THE CURVE

represents the total amount of drug that reaches the systemic circulation (the bloodstream)

ORAL DOSING MODEL

used to understand how drugs are absorbed into the body; use K and Ka

ABSORPTION RATE CONSTANT (Ka0

tells us the fraction of the drug present at the absorption site, which is typically the gastrointestinal (GI0 tract, that gets absorbed per unit of time

PERCENTAGE

we measure Ka as a _, representing the amount of drug absorbed over a specific time period

GREATER THAN 1

If Ka is _ within a given time unit, it means that almost all of the drug will be absorbed during that time interval (absorbed quickly into the bloodstream from the GI tract)