Drug-Receptor Interactions Flashcards
What is a drug?
A chemical substance that interacts with a biological system to produce a physiological effect.
What are the different drug target sites?
- Receptors - proteins within cell membranes (usually), activated by NT or hormone, defined by agonists & antagonists, 4 types of receptors
- examples of drugs: acetylcholine (agonist), atropine (antagonist) - Ion channels - selective pores - allow transfer of ions down electrochemical gradients, 2 types ( voltage-sensitive e.g. VSCC and receptor-linked e.g. nAChR)
- examples of drugs : local anaesthetics (VSSC) , calcium channel blockers - Transport systems - transport against concentration gradients (glucose, ions, NTs) specificity for certain species
- examples of drugs : Tricyclic anti- depressants (TCAs), Cardiac glycosides - Enzymes - catalytic proteins (increase rate of reactions)
Drug interactions:-
i) enzyme inhibitors e.g. anticholinesterases (neostigmine)
ii) false substrates e.g. methyldopa
iii) prodrugs
e.g. chloral hydrate -> trichloroethanol
What are agonists and antagonists?
agonist - a drug that stimulates a receptor - usually involves a conformational change in the receptor
e.g ACh
antagonist - blocks receptor e.g atropine
What affects potency?
affinity - avidity of which drug binds to receptor
efficacy - ability of drug to change conformation of receptor once its bound
What are full and partial agonists?
full = produces maximal response
partial = similar but not maximal response
*partial agonist can have some antagonist activity on full agonist (blocks some receptors)
What are the properties for antagonists? What are the two types of antagonists?
affinity but no efficacy ( bind but don’t do anything- block agonist)
2 types of receptor antagonist
- Competitive
-same site as agonist
- surmountable
- shifts D-R curve to right
Examples :atropine, propranolol
2.Irreversible
- binds tightly or at different site
- insurmountable
Example : hexamethonium
