Intro to pharmacology Flashcards
How does a drug work
By binding to something (e.g. receptors, enzymes, ion channels or transporters)
Define pharmacodynamics
The study of how drugs act on the living body
Define agonist
A ligand that binds and induces a response
Define full agonist
An agonist that produces a maximal effect. It has high efficacy
Define partial agonist
An agonist that produces a submaximal effect. It has an intermediate efficacy
What is the difference between a full and partial agonist
A full agonist produces a maximal effect, whilst a partial agonist produces a submaximal effect
What shaped dose-response curve does a full agonist give
Sigmoidal (S shaped)
What shaped dose-response curve does a partial agonist give
Sigmoidal (S shaped), but more shallow than a full agonist
Define a competitive antagonist
A ligand that competes with the agonist to bind to the receptor
Define a non-competitive antagonist
A ligand that binds to a site that is not the active site and alters the receptor such that the agonist cannot bind
Define a reversible antagonist
An antagonist that can be washed out. Binding is not permanent
Define an irreversible antagonist
An antagonist that cannot be washed out. Binding is permanent.
What is the dose-response curve for a reversible competitive antagonist
Parallel shift to the right. No change in maximal response
What is the dose-response curve for an irreversible competitive antagonist
No shift. Maximal response reduced
What is the dose-response curve for a reversible non-competitive antagonist
No shift. Maximal response reduced. No change in EC50 value
What is the dose-response curve for an irreversible non-competitive antagonist
No shift. Maximal response reduced. No change in EC50 value. Maintains sigmoidal shape.
Define physiological antagonism
A ligand that acts in a different place. Causes a different bodily function to counteract the undesirable one
Define chemical antagonism
An antagonist that reduces the concentration of an agonist by forming a chemical complex with it
Define pharmacokinetic antagonism
An antagonist that affects absorption, distribution, metabolism or elimination
Define affinity
The ability of the drug to bind to the target
Define efficacy
The ability of the drug to induce a conformational change (activation)
What is the affinity and efficacy of an agonist
Full agonists have high efficacy. Partial agonists have intermediate efficacy
What is the affinity and efficacy of an antagonist
They have no efficacy because no response is induced.
How does a ligand gated ion channel initiate a biological response
Agonist binding causes a conformational change which causes the ion channel to open
Give an example of a ligand gated ion channel
Nicotinic acetylcholine receptor
How does a GPCR initiate a biological response
Agonist binding causes stimulation of a secondary messenger signalling cascade
How does a receptor tyrosine kinase initiate a biological response
Similar to a GPCR. Except the intracellular domain contains tyrosine kinase
How does an intracellular hormone receptor initiate a biological response
Ligand activates transcription factors. Factors regulate gene expression by interacting with specific DNA sequences
What are the four key stages of pharmacokinetics
Absorption, Distribution, Metabolism, Excretion
Define drug absorption
How a drug enters the blood stream
What does drug distribution depend on
Physical and chemical properties of the drug. The drugs ability to penetrate cell membranes
Define the first pass effect and its importance
When drugs pass through the liver they tend to be converted to less active alternatives. Most drugs need to be able to be active after the first pass
Define EC50 value
The concentration of agonist needed to produce 50% of the maximal response
Define IC50 value
The concentration of antagonist needed to inhibit 50% of maximal response
Define ED50 value
Minimum dose required to show desired activity in half of the tested population after a specific duration of time
Define LD50 value
The dose required to kill half of the members of the tested population (LD = lethal dose)
Define therapeutic index
The ratio of ED and LC.
What is the importance of the therapeutic index
Defines a useable drug dose which will show activity, but not kill.
What are the four stages of a clinical trial
1 - check for safety2 - check for efficacy3 - confirm findings in a larger population group4 - test long-term safety in diverse patient population
Define ‘drug’
A substance of known chemical structure, which when administered to a living organism produces a biological effect
