Exam 1 - Drug Absorption Flashcards
hydrophilic
compatible with water
* water loving molecules
* carbohydrates and many proteins
hydrophobic (lipophilic)
not compatible with water
* water-fearing / fat-loving molecules
* lipids and some proteins
passive diffusion
process by which molecules move across a cell membrane from an area of high to low concentration
* lipid soluble
* hydrophobic
* small, uncharged molecules
carrier transport
process which specific proteins facilitate the movement of substances across the cell membrane, passively or actively, typically against the concentration gradient
Aqueous diffusion
the process by which water-soluble molecules passively move between cells through channels or pores in cell membranes
weak organic acid
compound that partially releases H+
weak organic base
compound that partially accepts H+
HA
non-ionized weak organic acid
H+ + A-
ionized anion
HB+
ionized cation
H+ + B
nonionized weak organic base
pH
measure of the amount of hydrogen ions [H+] in a liquid
low pH
signifies high acidity
high pH
signifies basic
Which substituents make drugs behave like weak organic acids?
- -COOH
- -OH
Which substituent makes drugs behave like weak organic bases?
- -NH2
drug ionization
process by which a drug gains or loses hydrogen ions in solution
pH partition hypothesis
- the ionization of a drug is influenced by the pH of the environment it is in
- this affects the drug’s absorption and distribution across biological membranes
influx transporters
only transport drugs INTO cells
* OATs (11 distinct proteins)
* OCTs (5 distinct proteins)
OATs
organic anion influx transporters
* transport a wide variety of organic acids
OCTs
organic cation influx transporters
* transport wide variety of organic bases
What are OATs and OCTs are typically called?
- drug influx pumps
- influx pumps
efflux transporters
only transport drugs out of cells
* MRPs (7 distinct proteins)
Where are transporters distributed?
intestinal cells, kidney cells, liver cells, brain blood vessels
What are drug transporters involved in?
- drug absorption
- drug excretion
- drug uptake and efflux by various cells and tissues
What factors affect drug absorption rate from all sites?
- blood flow
- surface area of administration site
- number of cell layer
- drug concentration gradient
What are factors affecting drug absorption rates from GI tract?
- gastric emptying time
- intestinal transit time
- binding to mucus and food – inhibits absorption
- first pass effect
In passive diffusion, which form of organic molecules can easily move across the cell membrane?
non-ionized drugs
In carrier transport, which form of organic molecules move through carrier proteins?
ionized forms
