Intro Pharmacokinetics vs Dynamics Flashcards
(36 cards)
Define a ‘Dose-Response Curve’
Curve which represents the dosage over which the drug is effective and peak effect/response that can be expected
Define ‘Threshold dose’
Where response begins and increases in magnitude until a response plateau is reached
Define ‘Ceiling effect (maximal efficacy)’
The point at which there is no further response even if dosage continues to increase
Define ‘efficacy’
Dosage ranges over which the drug has desired effect
Define ‘potency’
Threshold dose that produces a given response
The more potency a drug has the more it shifts to the left/right
LEFT
The taller the curve gets, the greater the potency/efficacy
EFFICACY
Define ‘median effective dose (ED50)’
The dose at which 50% of the population response to a drug in a specified manner
Define ‘median toxic dose (TD50)’
The dose at which 50% of the population exhibit adverse effects
Define ‘median lethal dose (LD50)’
The dose that causes death in 50% of the animals studied
Define ‘therapeutic index (TI)’
TD50/ED50; the higher the safer
Define ‘first pass effect’
When a drug is given orally, a significant portion is metabolized and destroyed in the liver, before it reaches the target tissues. A sufficient dosage must be given taking this destruction into account.
Define ‘bioavailability’
% of drug administered that reaches the bloodstream
What 4 factors affect bioavailability?
1) Tissue permeability (highly lipid molecules cross membranes more easily)
2) Blood flow (carries drug to highly perfused organs)
3) Plasma protein binding (bound portion of drug does NOT have a therapeutic effect and is NOT eliminated)
4) Subcellular protein binding (drug gets trapped within the cell
Define ‘volume of distribution’
Vd = amount of drug administered / concentration of drug in plasma
If Vd = total amount of body water?
Uniform body distribution
If Vd > total amount of body water
Drug is being concentrated in the tissues
If Vd
Drug is being retained in the bloodstream (i.e. due to plasma binding proteins)
What does activated charcoal do for overdose cases?
It creates a decreased concentration of the drug in the blood, so it has a negative concentration relative to the tissues and leaches the drug out and into the blood stream for excretion
Define ‘biotransformation’
Chemical altering of a drug to metabolite via enzymes to deactivate that drug
What is the primary site of drug metabolism?
Liver (also in the lungs, kidneys, GI, skin)
What factors affect biotransformation?
Tissue/ organ damage, metabolic inhibitors, enzyme induction
What are 4 biotransformation mechanisms?
Oxidation, Reduction ,Hydrolysis, Conjugation
How can herbs and supplements affect drug metabolism
They can inhibit the enzyme that metabolizes the drug
