BIO122 WK1 Pharmacokinetics

Pharmacokinetics

The study of how the body affects a drug, including absorption, distribution, metabolism, and elimination.

Absorption

The process by which a drug passes from its site of administration into the bloodstream.

Route of Administration

The method by which a drug is delivered, affecting the speed of absorption (e.g., IV, oral, transdermal).

IV Administration

A method that delivers drugs directly into the bloodstream for the fastest absorption.

Lipid Solubility

The ability of a drug to diffuse across cell membranes; lipid-soluble drugs diffuse easily, while water-soluble drugs require transport mechanisms.

Membrane Thickness

Thinner membranes (e.g., GI tract) allow for faster drug absorption compared to thicker membranes (e.g., skin).

Blood Supply

Areas with greater blood supply (e.g., lungs) facilitate faster drug absorption.

Drug Chemical Structure

Smaller, lipid-soluble molecules are absorbed more quickly than larger, water-soluble ones.

pH

The acidity or alkalinity of the environment affects drug ionization and absorption; for example, aspirin is better absorbed in an acidic environment.

Plasma Protein Binding

The binding of drugs to plasma proteins like albumin, affecting their availability and potential for drug interactions.

Distribution

The process by which unmetabolized drugs move from the bloodstream into tissues.

Organ-Specific Distribution

Certain organs preferentially uptake specific drugs; for example, the thyroid takes up iodine.

Blood-Brain Barrier

A selective barrier that restricts the entry of water-soluble drugs into the central nervous system (CNS).

Bioavailability

The proportion of a drug that reaches systemic circulation; IV administration has 100% bioavailability, while oral drugs typically have lower due to first-pass metabolism.

First-Pass Metabolism

The metabolism of a drug in the liver before it enters systemic circulation, reducing its bioavailability.

Elimination

The irreversible loss of a drug from the body, which can occur through various routes such as urine, feces, and lungs.

Urine Excretion

The process where most drugs are made more water-soluble for filtration, with possibilities for reabsorption and secretion.

Liver Excretion

Some drugs are excreted through the liver, attached to bile, which can prolong their action and clearance.

Calculating Bioavailability

Bioavailability can be expressed as a decimal or percentage, calculated by multiplying the administered dose by the bioavailability fraction.

Conceptual Understanding

Emphasizing the understanding of absorption, metabolism, and excretion processes rather than just calculations.