sulphonamides Flashcards
where do bacteria get folate in order to make DNA ?
they must make their own folate
what enzyme is inhibited by sulphonamides ?
in the process of folate synthesis , dihydropteroate synthase is inhibited
so no folate for bacteria
no DNA synthesis
which drugs are responsible for the inhibition of dihydrofolate reductase ?
trimethoprim pyrimethamine
what chemical is mimcd by sulphonamides ?
PABA
what are the methods of bacterial resistance against sulphonamide ?
increased PABA
altered dihydropterote synthase
decreased uptake
what drug is very similar to sulphonamide byt not a sulphonamide ?
dapsone
competes for PABA
what are the 2 main uses of dapsone ?
mycobacterium leprae
pneumocystitis jirovecii
what are the common clicnical scenarios associated with sulphonamide use ?
( trimethoprim , sulfamthazole combo ) called bactrim
sulfazidiazine cream used for burns
sulfadiazine and pyrimethamine used together for toxoplasmosis in HIV patients
what are the toxicities of sulphonamide ?
1- hypersensitivity reactions as with penicillin
( usually due to the presence of the N1 and N4 )
2- photosensitivity ( drug interaction with UV light)
3- classic trigger of hemolysis in G6PD because sulphonamides are oxidants
4- kernicterus , due to binding to albumin ( causes neurological involvement)
5- raises warfarin levels
why doesn’t a hypersensitivity reaction happen with other sulpha drugs ?
because you must have both the N1 and N4 groups for a reaction
what drugs are known to induce hemolysis in G6PD patients ?
dapsone
sulfonamides
how do antibiotics increase INR ?
the normal gut bacteria produces vitamin k
antibiotic disrupt the normal gut bacteria which in turn increases the effect of warfarin which then increases the INR
what are the toxicities associated with trimethoprim and pyrimathamine administration ?
1- bone marrow suppression ( pancytopenia)
how can bone marrow suppression induced by trimethoprim/pyrimethamine be treated ?
by using a leucovorin rescue
what type of antibiotic is bactrim ?
TMP-SMX
which is a bactericidal
usually bacteriostatic but become bacteriicidal when mixed with trimethoprim
what are the common uses of bactrim ?
UTI infection
pneumocystis pneumonia in HIV
why isnt bactrim given during pregnancy ?
decreases folic acid
higher risk of kernicterus
what is the treatment of choice in pnemocytis jiroveci ?
bactrims but HIV patients experience a higher chance of hypersensitivity reactions so dapsone is used instead
