Exam 2- Lecture 6 (Dosage Form Design Biopharmaceutical Considerations) Flashcards
The rate at which a drug reaches it site of action depends on what?
Absorption
Distribution
What is absorption?
Passage of drug from its site of administration into the blood without being altered
What is distribution?
Delivery of drug to tissues
What is the passageway of an oral medication?
GI-Circulation
What is the passageway of an IV med?
Circulation- goes directly blood stream so it doesn’t have to get absorbed.
What is the passageway of IM/ SQ?
Tissue-Circulation
What are the three types of physiological factors that affect drug absorption? Give examples
Barriers- biological membranes: several layers of cells, single layer of cells etc.
Absorption passageway- Passive diffusion, and specialized transport.
GI physiology: gastric motility and emptying, influence of food and pH
What are the two examples of passive diffusion? Describe.
Transcellular: particles pass through the cell
Paracellular: particles pass in between cells
What law can describe passive diffusion? What are the variables?
Fink’s law: rate of diffusion A surface area of membrane D diffusion coefficient h thickness of membrane C1 and C2 are the concentrations on each side of membrane
What is meant by sink conditions?
Where you have very high concentration on one side and a small neglectable concentration on the other side.
Sink conditions give you what type of equation?
First order kinetics
Rate of diffusion is directly proportional to the initial concentration
What is partition coefficient?
Concentration dependent but also relative to the affinity for lipid and water.
Diffusion coefficient of a drug depends on the particle size.
What form is absorbed? Unionized or ionized?
Unionized
What drives passive diffusion for weak acids and bases?
Unionized fraction
pH of the surrounding environment dictates _________ while _________ dictates the drug.
% of unionized form
pKa
What is carrier mediated transport and what are the types?
Carrier mediated transport: the passage of molecules of transporter or carrier
Active and facilitated transport
What are the similarities between active transport and facilitated diffusion?
Specific: size and shape
Saturable: too much molecules not enough transporters
Inhibitable: something with similar shape and size can interact with the carrier or transporter inhibiting the molecule from interacting.
What are the differences between active transport and facilitated diffusion? Name examples
Active transport: requires energy, and is against concentration gradient.
Cancer drugs: methyldopa, 5-florouracil
Facilitated diffusion: doesn’t require energy, moves along concentration gradient (high-low). Furosemide, morphine, penicillin
What are the types of transcytosis?
Phagocytosis: “cell eating”
Pinocytosis: “cell drinking”
Receptor mediated endocytosis
