Biopharmaceutics Flashcards
What is the focus of biopharmaceutics?
The study of how the physicochemical properties of a drug, its dosage form, and route of administration affect the rate and extent of drug absorption.
What is pharmacokinetics?
The study and characterization of the time course of drug absorption, distribution, metabolism, and elimination.
What is pharmacodynamics?
The study of the biochemical and physiological effects of the drug on the body.
List the four main processes involved in pharmacokinetics.
Absorption, Distribution, Metabolism, and Excretion (usually by the kidney).
What happens to polar drugs in the body?
They are usually excreted in urine; if needed, the liver metabolizes them to make them more polar.
What factors govern drug distribution in the body?
Affinity for various tissues, aqueous or lipid solubility, binding to extracellular substances (e.g., proteins), and intracellular uptake.
What is passive diffusion?
The movement of molecules via a concentration gradient across a membrane, without a carrier, non-saturable, and with low structural specificity.
How do most drugs gain access to the body?
Through passive diffusion.
What is the composition of cell membranes in living organisms?
They are composed of a lipid bilayer, which also applies to sub-cellular structures.
What function does the lipid bilayer serve in cell membranes?
It acts as a barrier, preventing ions, proteins, and other molecules from diffusing in or out of cells.
Why are most water-soluble molecules unable to pass directly through the lipid bilayer?
The bilayer is impermeable to them, so cells use ion pumps to regulate salt concentrations and pH by moving ions across the membrane.
What are natural bilayers primarily made of?
Phospholipids with a hydrophilic head and two hydrophobic tails.
Why do polar molecules have low permeability across the lipid bilayer?
They have low solubility in the hydrocarbon core of the lipid bilayer, resulting in low permeability coefficients.
What does the lipid:aqueous drug partition coefficient describe?
It describes the ease with which a drug moves between aqueous and lipid environments
Why is the ionization state of a drug important?
It determines how well the drug will move across a lipid membrane; charged drugs have difficulty diffusing through lipid environments.
