Pharmacology: Principles Flashcards
(35 cards)
What is pharmacodynamics?
What the drug does to the body
What is pharmacokinetics?
What the body does to the drug
What can drugs target?
Enzymes (e.g. ACE inhibitors, aspirin, neostigmine)
Carrier Molecules (e.g. flavonoid – Pgp antagonist, digoxin)
Ion channels (e.g. verapamil - L-type calcium channel antagonist)
Receptors (e.g. benzodiazepine – GABA receptor agonist, adrenoceptor agonists and antagonists )
Structural proteins (e.g. Taxol – Tubulin “agonist”)
DNA (e.g. anti cancer agents like Doxorubicin)
What are receptors?
Receptors are Protein molecules whose function is to recognise and respond to endogenous chemical signals.
Chemicals which mimic the endogenous signals (i.e. drugs) will also elicit an effect.
What us an agonist?
molecule/drug that binds and activates the receptor
What is affinity?
the tendency of a drug to bind to the receptor
What is efficacy?
the tendency of a drug to activate the receptor once bound
If the activation is 100%, namely each time a drug interacts with its target there is a response then the agonist is said to be a “full agonist”, If the activation is <100%, the agonist is said to be a ….
Partial agonists, which have lower efficacy than full agonists – even with maximal occupancy of receptors.
What is EC50?
Effective concentration. The dose required for an individual to experience 50% of the maximal effect.
What is ED50?
Effective dose. The dose for 50% of the population to obtain the therapeutic effect.
What is the therapeutic index?
Therapeutic index = toxic dose (TD50)/ Effective dose (ED50)
What therapeutic index does the ideal drug have?
A high one
What is potency?
The amount of drug required to produce 50% of its maximal effects. Used to compare drugs within a chemical class (usually expressed in milligrams/kg).
What is efficacy?
The maximum therapeutic response that a drug can produce (example: morphine vs buprenorphine)
What is specificity?
Describes the capacity of a drug to cause a particular action in a population (for example, a drug of absolute specificity of action might decrease or increase, a specific function of a given gene or protein or cell type, but it must do either, not both).
What is selectivity?
Relates to a drugs ability to target only a selective population i.e. a cell/tissue/ signalling pathway, protein etc in preference to others
Do antagonists have efficacy and affinity?
Antagonist have affinity but zero efficacy (as they block the target activity)
What are the two main types of antagonism?
Competitive, Non-competitive and Irreversible
How does competitive antagonism work?
Competitive agonists compete with agonists for the receptor binding site.
The chemical structure of the agonist and competitive antagonist are often similar (lock and key hypothesis).
Antagonist binds to receptor in such a way as to prevent agonist binding
Competitive antagonism is surmountable – additional agonist can overcome the receptor blockade.
How does non-competitive antagonism work?
Non-competitive antagonists either bind to a different receptor site OR block the chain of events “post” binding - acting “downstream” of the receptor.
How does irreversible antagonism work?
Antagonist dissociates from the receptor only very slowly or not at all.
The antagonist forms covalent bonds with the receptor.
Irreversible antagonism is insurmountable – additional agonist cannot overcome the receptor blockade
What is IC50?
Concentration of antagonist to inhibit 50% of the agonist maximal
What is inverse agonism?
An agent that binds to the same receptor as an agonist but induces a pharmacological response opposite to that agonist.
What is tachyphylaxis?
(“rapid protection”): Reduction in drug tolerance which develops after a short period of repeated dosing (decrease in response). Not common. Often due to a lack of a co-factor.
