Drug Absorption Flashcards
What are the 4 factors that influence drug membrane passage?
- Size
- Lipid Solubility
- Concentration Gradient
- Degree of ionization (pH effects)
Generally, which transports larger drugs, Passive lipid diffusion or passive aqueous diffusion?
Lipid
aqueous diffusion relies on protein channels
Which does is rate of absorption most important for?
The First dose. All other doses just maintain a therapeutic level.
What is/are the optimum characteristic(s) of drugs with high oral bioavailability?
Hydrophobic yet soluble in aqueous solutions
Describe the onset of action and bioavailability for Oral Administration of a drug.
Slow onset Variable bioavailability (0-100%)
Describe the onset of action and bioavailability for Rectal Administration of a drug.
Not rapid
Variable Bioavailability but usually better than oral
Describe the onset of action and bioavailability for Sublingual Administration of a drug.
Minutes
Availability near 100% (high)
Describe the onset of action and bioavailability for IV Administration of a drug.
Immediate
100% by definition
Describe the onset of action and bioavailability for IM Administration of a drug.
Rapid (5-10 min for aqueous solutions)
Approaches 100%
Describe the onset of action and bioavailability for Subcutaneous Administration of a drug.
Slower, constant rate of absorption (birth control)
Approaches 100%
Describe the onset of action and bioavailability for Inhalation/Nasal Administration of a drug.
Rapid
approaches 100%
What is the optimum sized particle for inhalation drugs?
1-5 uM.
Smaller has no effect, larger has side effects.
What is the 1st pass effect?
Metabolism of drugs by liver or acidic parts of the stomach. Ect.
Which absorbs drugs faster, stomach or small intestine?
SI because of surface area.
Steady state is reached
4-5 times of half life
