Drug Absorption Flashcards
What are the 4 jobs of a doctor?
Curing patients
Harming patients
Hospitalization
Death
What is pharmaceutical process?
Getting the drug into the patient.
What is the pharmacokinetic process?
Getting the drug to the site of action.
What is the pharmacodynamic process?
Producing the correct pharmacological effect.
What is the therapeutic process?
Producing the correct therapeutic effect.
What are the 4 basic factors that determine drug pharmacokinetics? ADME
Absorption
Distribution
Metabolism
Elimination
What 5 things does ADME help us understand?
Dosage Drug administration Drug handling Patient variability Potential for harm
Define absorption.
The process of movement of unchanged drug from the site of administration to the systemic circulation.
What is there always a correlation between plasma concentration and?
Therapeutic Response
What are the 2 important issues of oral absorption?
Amount of drug which enters the systemic circulation.
Speed at which this happens.
The more rapid the rate of absorption, the ______ the drug concentration peak.
Earlier
Increasing dose does/does not affect the time at which peak concentration is reached but does/ does not increase the peak concentration.
Does not
Does
The area under the drug concentration-time curve represents the amount of drug which reaches the ______ circulation.
Systemic
What is therapeutic range?
The range of concentrations a drug is active at.
What happens if the concentration of drug is greater than the therapeutic range?
Toxicity
What happens if the concentration of drug is lower than the therapeutic range?
Insufficient or no pharmacological action.
What is the therapeutic index?
Measure of the range at which a drug is safe and active.
What does AUC allow to be measured?
Estimate the amount of drug which reaches the circulation and which is available for action.
A drug given intravenously has ___% bioavailability.
100
What are the 4 factors affecting bioavailability?
Formulation
Ability to pass physiological barriers
GI effects
First pass metabolism
What are the different types of physiological barriers?
Passive diffusion
Filtration
Bulk flow
Active transport
Are drugs mainly strong or weak acids/bases?
Weak
Does ionised or unionised drug pass through the membrane?
Unionised
An acidic drug will be more concentrated in the compartment with high pH. What is this called?
Ion trapping
The relationship between the local pH and the degree of ionisation is described by?
Henderson-Hasselbalch equation.
Where SHOULD aspirin be more easily absorbed?
The stomach
Where is aspirin more easily absorbed and why?
Small intestine due to the available gut surface.
What 2 things must a drug be to pass across a lipid layer?
In solution
Lipid soluble
What is the lipid-water partition coefficient?
Ratio of the amount of a drug which dissolves in the lipid and water phase when they are in contact.
A drug that is highly lipid soluble will diffuse slowly/rapidly across a cell membrane.
Rapidly
Which of these are true: Passive diffusion: Is common Occurs along conc. gradient Selective Saturable Requires energy No carrier
Common
Occurs along concentration gradient
No carrier
Which of these are true: Active absorption: Is common Occurs against concentration gradient Requires carrier Doesn't require energy Not specific Saturable
Occurs against concentration gradient
Requires carrier
Saturable
What 4 elements are associated with active absorption?
Iron
Potassium
Sodium
Calcium
What must drugs resemble to undergo active transport?
Naturally occurring compounds.
Which of these are true: Facilitated diffusion: Occurs against the concentration gradient Requires carriers Saturable Not specific No energy required
Requires carriers
Saturable
No energy required
What size and weight must molecules be to undergo filtration?
Smaller than the diameter of the pore with a molecular weight of 100 or less.
What drives filtration?
Hydrostatic/Osmotic pressure
What are the 3 GI factors?
Motility
Food
Illness
What is first pass metabolism?
Metabolism of drug prior to reaching systemic circulation.
Where are 3 examples of places where first pass metabolism occurs?
Gut lumen
Gut wall
Liver
What can intramuscular routes change?
Rate of absorption with different physical properties of formulation.
What does intramuscular route avoid?
First pass metabolism
How do sublingual/buccal drugs get given?
Straight into the circulation.
Why are rectum drugs often given?
To stop irritation of stomach.
What type of process is best for volatile agents?
Inhalation/nasal
What do transdermal drugs need to be?
Non-irritant.
What are the 5 considerations for mode of administration?
Site of drug Disease affects Patients ability Speed of action Reliability of absorption
