Sulfonamides Flashcards
what is the distribution of sulfonamides?
can penetrate intracellularly
used for systemic effect have wide distribution
can vary by agent
are sulfonamides used orally in ruminants for systemic effects?
yes
sulfonamides compete with ________________________________ for incorporation into the scheme for folic acid synthesis. folic acid is used for ___________________. this biological antagonism leads to decreased RNA, inhibiting protein synthesis
para amino benzoic acid (PABA)
purine synthesis
why are mammalian cells not susceptible to the mechanism of action of sulfonamides?
use preformed folic acid
why does purulent debris decrease sulfonamide activity?
high protein content
perhaps high para amino benzoic acid content
cross-resistance between sulfonamides is considered ________________
complete
what are some intermediate-acting sulfonamide agents?
sulfadimethoxine
sulfamethoxazole
sulfadiazine
what is the clinical relevance of sulfonamides?
too much resistance for empiric use
what are the selected uses for sulfonamides?
coccidiosis
nocardia
bovine foot rot
use in combination with other agents to enhance antimicrobial and antiprotozoal activity
what is a type A (1) adverse effect of sulfonamides?
crystalluria
what are some things seen in type B (2) adverse effects of sulfonamides?
keratoconjunctivitis sicca
IMHA/ITP
polyarthropathy
hepatotoxicity
proteinuria
cutaneous drug eruptions
hypothyroidism
what is the distribution of diaminopyramidines/benzylpyrimidines?
cross barriers well including the blood brain barrier and concentrates in prostate
how are diaminopyramidines/benzylpyrimidines excreted?
renal excretion and concentration for trimethoprim (most commonly used)
what is the mechanism of action of diaminopyramidines/benzylpyrimidines?
inhibit dihydrofolate reductase thereby interfering with purine and pyrimidine synthesis
why are diaminopyrimidines often combined with a sulfonamide to create a potentiated sulfa?
resistance development is often quick when used as a sole agent
what are some common potentiated sulfas?
trimethoprim + sulfadiazine: TMS
trimethoprim + sulfamethoxazole
what is an important type A side effect due to the diaminopyrimidine in potentiated sulfas?
bone marrow suppression
one important type B adverse effect of potentiated suflas due to the diaminopyrimidine: simultaneous injections of _____________________ and injectable TMS has caused death in horses
alpha-2 agonists
which sulfonamides distribute to the CNS at effective concentrations?
sulfadiazine/sulfamethoxazole: sulfas used in TMS
do sulfonamides concentrate in urine?
yes
are sulfonamides bacteriostatic or bacteridicidal?
bacteriostatic
what is the efficacy of sulfonamides dependent upon?
time above MIC
what is an enteric sulfa agent?
sulfazalazine
what are some regulatory issues with sulfonamides?
use of sulfonamides in lactating dairy cattle, other than those medications specifically approved for use, has been labeled as high priority by the food and drug administration
