Inhibitors of DNA Function Flashcards
what are the 3 inhibitors of DNA function
- fluoroquinolones
- nitrofurantoin
- metronidazole
which fluoroquinolone has good pseudomonal coverage
cipro
which fluoroquinolone has good urinary and respiratory coverage
levo
what fluoroquinolone has good gram (+) coverage
moxi
what part of bacteria do fluoroquinolones target
bacterial DNA gyrase and topoisomerase IV
what is the fxn of bacterial DNA gyrase
required for normal DNA replication → transcription and some aspects of DNA repair and recombination
DNA inhibitors inhibit DNA __
precursors
what is fluoroquinolones MOA
bactericidal → rapid w.in 2 hr
how does strep pneumo develop resistance against fluoroquinolones
point mutations in DNA gyrase/topoisomerase
strep pneumo resistance to fluoroquinolones is a __ process
step wise
strep pneumo prevents drug-target against fluoroquinolones via ___
and ___ gene
drug efflux
MDR
what is the holy trinity of URI infxn
strep pneumo
m. cat
h. flu
what are the respiratory quinolones
levo
moxi
which quinolone covers bacillus anthracis
cipro
quinolones should only be used in
very serious infxns
→ ex don’t use levo for m.cat for sinusitis or bronchitis
cipro and levo should be used for pseudo and e.coli only in
complicated UTIs
which quinolone has good coverage against atypical organisms (chlamydia, mycoplasma pneumoniae, rickettsia)
moxi
fluoroquinolones are well absorbed __
and also available __
orally
IV
fluoroquinolones have good penetration into most tissues, including high __
urinary levels
fluoroquinolones are primarily excreted by the __,
except for __
kidneys
moxi
renal dosing is needed for levo and cipro, but not for __
moxi
fluoroquinolones are generally well tolerated, the most two common adverse rxns are mild
- GI tract
- CNS (HA, dizzy, insomnia)
what are the 2 box warnings for quinolones
- 3-4 fold risk of tendon rupture → rare
- potential for athropathies → limits use in pregnancy and children <12 yo
what cardiac adverse effect do quinolones have
prolonged QT interval
what are the 3 drug-drug interactions w. quinolones
- antacids
- theophylline and caffeine
which quinolone are drug-drug interactions most associated with
cipro
theophylline rxn w. cipro is of less importance now bc
theophylline is hardly ever used
nitrofurantoin is most commonly used for
urinary tract antiseptic
nitrofurantoin is not used for __ infxns
bc __ can not be obtained w. safe doses
systemic
effective Cp
nitrofurantoins are ___
by __
to intermediates that
___
reduced
bacterial enzymes
damage bacterial DNA
nitrofurantoins are generally (cidal or static)
bactericidal
why is nitrofurantoin selectively toxic
bc mammalian enzymes don’t reduce nitrofurantoin as rapidly
nitrofurantoin is used for what class of bacteria
gram negative rods
nitrofurantoin is used for what type of infxn
uncomplicated UTIs
nitrofurantoin works well against __
but __
and __ are resistant
e.coli
pseudomonas and proteus
nitrofurantoin has rapid and complete __ absorption
oral
nitrofurantoin is excreted into the ___
and requires __ dosing
urine
renal
use of nitrofurantoin is contraindicated in
renal insufficiency
mabrobid is
bid nitrofurantoin
macrodantin is
qid nitrofurantoin
most common adverse rxns of nitrofurantoin occur in the
GI tract
___ forms of nitrofurantoin are better tolerated
macrocrystalline
what are 3 serious adverse rxns of nitrofurantoin
- hemolytic anemia
- neuropathies → chronic use
- category B for pregnancy → but should NOT be given in 3rd trimester dt hemolytic anemia
metronidazole is a __ transformed to reactive radicale in organisms
with __
prodrug
negative redox potential
metronidazole is effective against what 2 bacteria
- anaerobic
- protozoa
metronidazole kills via
DNA strand breaks
inhibition of replication
metronidazole is (static or cidal)
cidal
resistance to metronidazole is via __
which ___
expression of nitroimidazole reductase
stops formation of nitroso-group
metronidazole has esecially good activity against which anaerobes
- bacteroides
- c.diff
the bioavailability of metronidazole is __
and absorption is not __
80%
affected by food
metronidazole has good distribution, including __
and __
CSF
bone
metronidazole is primarily metabolized via __ metabolism,
and __ dosing is required
hepatic
liver
what is a concern for nursing moms with metronidazole
it is excreted in breast milk
drug interactions w. metronidazole are possible w.
CYP450 inhibitors
the most common adverse rxns with metronidazole are (4)
nausea
HA
dry mouth
metallic taste
metronidazole is contraindicated in pregnancy during the __
1st trimester
metronidazole can have a drug-drug interaction w.
etoh
what are the 2 inhibitors of intermediary metabolism
- sulfonamides
- trimethroprim/sulfamethoxazole
resistance to sulfonamides is widespread and persistent in vivo in
meningococci
gonococci
b-hemolytic strep
enteric gram-negative rods
what are the 2 mechanisms of acquired resistance to sulfonamides
- increased production of PABA
- altered DHPS
resistance to sulfonamides occurs in a __ fashion,
not during __
stepwise
therapy
bacteria obtain DNA precursors from __,
which is why ___ is important
pus
surgical drainage
organisms with no __ requirement are not susceptible to sulfonamides
folic acid
sulfonamides are synergistic w. ___
trimethoprim
sulfonamides are (cidal vs static)
cidal
is trimethoprim a sulfonamide
no!
trimethoprim is __ more potent
than __
5-20%
sulfonamides
resistance to sulfonamides is via
altered DHFR
what is DHFR
dihydrofolate reductase
pyrimethamine inhibits __ DHFR
which is __
protozoal
malaria
methotrexate inhibits ___ DHFR
which is ___
mammalian
neoplasms
the target of sulfonamides is
the enzyme that makes folic acid
trimethoprim targets
another step of folic acid formation
does TMP/SMX cover MRSA
yes
sulfonamides plus trimethoprim work well for what types of gram negative infxns
uncomplicated UTI → e. coli
burn infxns → pseudomonas
sulfonamides are ___ that are well absorbed
from the ___
weak acids
GI tract
sulfacetamide is
topical sulfonamide + trimethoprim
sulfacetamide is used for
conjunctivitis
sulfonanides should be taken
on an empty stomach
sulfonamides have good distribution in body water, including (4)
- pleural
- ocular
- synovial fluids
- CSF
sulfonamides can cause displacement of ___
in ___,
predisposing them to ___
bilirubin
neonates
kernicterus
what can be a source of drug-drug interactions with sulfonamides
displacement of protein-bound drugs
sulfonamides are not used in what pt population
neonates
pregnant women
the major metabolic pathway for sulfonaides is __,
which may be toxic dt ___
n-acetylation
low solubility in urine
do sulfonanides require renal dosing
yes
sulfonamides should be taken with
lots of fluids
sulfonamides are the worst drug for what type of rxn
hypersensitivity rxns
what is a severe adverse rxn with sulfonamides
stevens-johnson