non competitve antagonist??? - stranger016

[ArchivalUser]

Can non-competitive antagonist behave as competitive antagonist at low dose????
anyone please explain the concept
thanks

[ArchivalUser]

Anyone has any idea about it guys???

[ArchivalUser]

they are noncompetitive always at any dose, they bind to a different site than the substrate site but the bond can be covalent(reversible) or noncovalent(irreversible)

http://www.usmleforum.com/showthread.php?tid=759513
NONCOMPETITIVE INHIBITORS
a. reversible (allosteric)binding
-The drug binds to an allosteric site(regulatory site)
-many feedback inhibition by allostric regulators in biochem reactions

b. irreversible binding
-Organophosphates (insecticides used by farmers) causes noncompetitive irreversible inhibition of acetylcholinesterase

-ASPIRIN is the only NSAID that is noncompetitive irreversible inhibitor of COX. The other NSAIDs are competitive inhibitors of COX
-Penicillin acts by covalently modifying the enzyme transpeptidase, thereby preventing the synthesis of bacterial cell walls and thus killing the bacteria

[ArchivalUser]

thanks for that miracoli..
have u done NBME 11,if yes the can u please explain this question from NBME 11 Block 2 Q 20


http://www.usmleforum.com/showthread.php?tid=762275