2 Absorption and Distribution Free Online FlashCards

What is drug absorption?

Absorption is the movement of a drug from its administration site into systemic circulation.

What is drug distribution?

Distribution is the reversible movement of a drug between the blood and body tissues.

Why do IV drugs bypass absorption?

IV drugs enter systemic circulation directly, so they bypass absorption as a pharmacokinetic step.

How do bioavailability and absorption rate differ?

Bioavailability describes the extent of systemic availability; the rate of absorption affects how quickly drug concentrations rise.

Which drug properties can affect absorption?

Solubility, particle size, formulation, and ability to cross membranes can affect how readily a drug becomes available for absorption.

Which tissues generally receive a drug sooner?

Well-perfused tissues generally receive a drug sooner than tissues with lower blood flow.

What do small and large apparent volumes of distribution suggest?

A small apparent volume of distribution is consistent with more drug remaining in blood; a large value suggests extensive distribution into tissues.

Why can oral drugs have reduced bioavailability?

Oral drugs may be incompletely absorbed, and some may be metabolized in the intestinal wall or liver before reaching systemic circulation.

How can sublingual and buccal routes limit first-pass metabolism?

Sublingual and buccal drugs are absorbed through tissues under the tongue or in the cheek, avoiding much of gastrointestinal absorption and hepatic first pass.

What determines how much rectal absorption avoids first-pass metabolism?

The extent to which rectal absorption avoids first-pass metabolism varies with the site of absorption.

What influences absorption after IM or SC injection?

Absorption from IM and SC injection sites is influenced by local blood flow and the drug formulation.

How can absolute bioavailability be estimated?

Compare dose-normalized AUC after the non-IV route with dose-normalized AUC after IV administration. Half the IV exposure corresponds to approximately 50% absolute bioavailability.