Pharmacokinetics Flashcards
What does ADME stand for
Absorption
Distribution
Metabolism
Excretion
Drug definition
A chemical substance of known structure (non nutritional) which produces a biological effect when administered
How are drugs categorised (Anatomical classification system)
Physiological system (target area eg - blood, respiratory system)
Therapeutic group (effect eg - stimulants, contraceptives)
Chemical properties (structure)
Most common/successful drugs
Lisoprinal (ACE inhibitor)
Atorvastatin’s (for high cholesterol)
Penicillin (200mil lives saved)
Major drug failure examples
Thalidomide (treated morning sickness but caused serious birth defects & maternal death
Relentlessly incurable diseases
the Cold, Alzheimer’s, Diabetes I
Common drug administration methods
Oral, Rectal, Intravenous, Nasal, Sublingual, intramuscular, inhalation, Transdermal, intrathecal
How are most small molecule drugs delivered, where is absorption & contributing physiological factors
Orally - absorbed in SI
Gut content, GI motility
How do drugs move across membranes
Simple diffusion (through lipids)
Facilitated diffusion (through aqueous channels)
Carrier protein transport (ATP dependant or independent)
Which conditions aid the movement of drugs
- high conc grad
- low molecular weight
- low degree of ionisation
What is the first pass effect
a large reduction in concentration of orally taken drugs before reaching systemic circulation (reduces bioavailability)
Where does the first pass effect take place and how
The gut or liver - following absorption the drugs maybe travel through the portal vin to the liver where they are metabolised
Bioavailability definition
How much of a orally given drug makes into circulation in is active form
IV vs oral administration (bioavailability)
IV reaches blood much quicker and at greater concentrations (but is also undergoes a rapid elimination process)
Oral bioavailability equation
AUC = area under curve
Oral bioavailability = AUC oral
/ AUC iv
what does Oral bioavailability calculation show (eg for a 50% result)
for a 50% result the dose must be doubled when converting from intravenous to oral route
Oral administration pros/cons
pros - easy to administer
cons - subject to first pass effect
Rectal administration pros/cons
pros - can be used for vomiting patients
cons - bioavailability varies depending on blood supply
Inhalation administration pros/cons
pros - local effect, very fast
cons - not suitable for large molecules (can leak into systemic blood)
Intravenous administration pros/cons
pros - 100% bioavailability
cons - enters tissue rich in blood vessels first
Intrathecal administration pros/cons
pros - cross the blood-brain barrier
cons - difficult to administer
Transdermal administration pros/cons
pros - not subject to first pass effect
cons - bioavailability depends on the subcutaneous muscle/fat
Alcohol absorption (empty stomach)
- Some absorbed in stomach most moves into SI where it is rapidly absorbed
Alcohol absorption (after a meal)
- Pyloric sphincter is closed so alcohol is kept in stomach longer where is it slowly absorbed
