04 - Antagonists and Dose Response Curves (pharmacodynamics) Flashcards
Pure antagonists don’t cause any…
Action by binding to the receptor (they just block it) 🙅♂️
3 Classes of antagonist…
- Chemical
- Physiological
- Pharmacological
Chelating agents are examples of which type of antagonist?
Chemical
Pharmacological (drug) antagonists can be divided into 2 categories based on binding site…
- Active site binding
* Allosteric site binding
Pharmacological (drug) antagonists can be divided into 2 categories based on the nature of the binding…
- Reversible
* Irreversible
Reversible active site antagonists are ( competitive / non-competitive )
Competitive
Irreversible active site antagonists are ( competitive / non-competitive )
Non-competitive
Both reversible and irreversible allosteric site antagonists are ( competitive / non-competitive)
Non-competitive
as they do not bind at the active site
Competitive antagonists will shift the response curve to the…
Right
as it will decrease the response at a given dose or concentration
The effectiveness of a competitive antagonist can be quantified with the…
Dose ratio
Schild equation
r - 1 = [B] / Kb
Where r - 1 is the dose ratio and [B] is concentration of antagonist
The Schild plot only works for…
Competitive active site antagonists (because the slope = 1, linear)
pA2 =
-log Kb
Irreversible antagonists decrease…
EC50
Which type of antagonism is most common, competitive or irreversible?
Competitive
An example of competitive antagonism is…
Tamoxifen at the estrogen receptor
Cimetidine at H2 receptor
An example of irreversible antagonism is…
Phenoxybenzamine at alpha-1 adrenoreceptors
The dose-response curve of a non-competitive antagonist looks like that of…
An irreversible antagonist
The dose-response curve of a partial agonists looks like that of…
A full agonist with an irreversible antagonist
The theraputic index or window the is the area between…
The onset of desired affects and adverse effects
Theraputic index
TD or LD 50 / ED50
