BP 4 – Antagonist and dose-response curves Flashcards
What type of drug is terferadine and at what receptor does it attach?
Antihistamine attaching at a H1 receptor
What is the function of a pure drug antagonist?
No action by binding to the receptor
What is the function of propranolol as an antagonist?
Propranolol attaches to the ß adrenoreceptor, forming a complex and lowers BP
What 3 classes of antagonists are there? and explain them.
Chemical - binding of 2 agents making an active drug inactive
Physiological - 2 agents with opposite effects cancelling each other out
Pharmacological - drugs that bind to a receptor and block action of agonist
What antagonist class are chelating agents?
Chemical
What is the efficacy of an antagonist?
NO efficacy
What happens if a competitive agonist attaches to the active/orthosteric site? and also what happens to the agonist-response curve?
Binds and prevents agonist action, however overcome with increased agonist
Curve shifts right
What happens if a non-competitive (irreversible) agonist attaches to the active/orthosteric site? and also what happens to the agonist-response curve?
Binds to form irreversible covalent bonds with receptors
Curve shifts right and reduced max asymptote
What happens if a non-competitive (irreversible) agonist attaches to the allosteric site? and also what happens to the agonist-response curve?
Signal transduction rather than receptor effects
Downstream responses are blocked
Reduced slope and max asymptote of curve
For an antagonist response curve, an agonist must be present as well, why?
Agonist has to be present with the antagonist to be able to drive the experiment and to see the effect of the antagonist, or else there would be no effect on the curve
How does a dose-response curve show the presence of a competitive antagonist?
- Agonist curves have the same form
- Antagonist curves are displaced to the right
- Agonist curves have the same maximal response
- The linear portion of the curves are parallel
If the Schlid plot is equal to 1, what type of antagonist is it?
Competitive antagonist
What does antagonist inhibition depend on?
Concentration of the competing agonist
Concentration of the antagonists concentration - due to different metabolisms and clearance influence plasma concentrations
What is the difference in dose-response curve of an irreversible antagonist?
Reduced max response
Binds irreversibly with the receptor, giving rise to antagonism which can’t be overcome even when increased concentration of agonist
Increased EC50
Which antagonist is more common: Competitive or irreversible?
Competitive
