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.
How do pH and drug pKa influence drug absorption?
They determine the drug’s ionization state, which significantly affects its transport across membranes.
Which equation is used to determine the ionization state of a drug?
The Henderson-Hasselbalch equation.
How do water-soluble drugs penetrate the cell membrane?
They penetrate through aqueous channels.
What is Facilitated Diffusion?
- Involves Carrier protein and is a saturable process
- No extra energy needed
E.g Large water soluble/ Polar compound
What is Active Transport?
- Requires Energy
- Transport is against the concentration gradient
Why is Active transport important?
Important mechanism for passage of larger drug molecules
-carriers involved
What is Endocytosis and Exocytosis
They mediate the entry into cells by very large substances
-e.g movement across Intestinal wall into blood of vitamin B12 complexed with its binding protein
-e.g solid particles/ Oil Particles, 1-100nm
What is Bioavailability
It’s the measure of the mount of drug from the formulation appears in the plasma (systemic circulation)
I.e measure the rate and extent of absorption
What does a therapeutic response on a drug depend on
Adequate concentration at site of action
How is Bioavailability calculated?
It’s calculated by determining the AUC from a blood plasma drug concentration V.S. time plot
- Non I.V.: Ranges from 0 to 100%
- IV : 100%
What does MEC mean?
Minimum Effective Concentration
-Required for the desired Pharmacological effect
What does MSC mean?
Maximum Safe Concentration - above which toxic effect occur
What does the Therapeutic Window mean?
Desired response with no toxic effects
What does Bioequivalence mean?
Comparing two dosage forms containing same drug are equivalent in terms of rate and extent of absorption
What does bioequivalence use?
Uses AUC, Cmax, tmax
