Inhibitors of Nucleic Acid Function or Synthesis

Question 1

What do topoisomerases do?? how do they act?

Answer 1

Topoisomerase: A class ofenzymes that alter the supercoiling of double-stranded DNA. 
The topoisomerases act by transiently cutting one or both strands of the DNA.

Question 2

name the four generations of fluoroquinolones

Answer 2

1st gen - nalidixic acid, neggram
2nd gen -
 ciprofloxacin (cipro), norfloxacin (noroxin), ofloxacin (floxin)
3rd gen - levofloxacin (levaquin)
4th gen - moxifloxacin (avelox)

Question 3

what is the MOA if fluoroquinolones

Answer 3

they enter by passive diffusion through porins. inhibit replication of bacterial DNA by interferring with bacterial DNA gyrase (topoisomerase 2) during replication. they bind to both enzyme and DNA forming a complex leading to cell death by DNA cleavage.

Question 4

fluoroquinolones are bacteriostatic. t/f?

Answer 4

false. they are bactericidal.

Question 5

which gram - organims are fluoroquinolones effective against?

Answer 5

enterobacteria, moraxella cattrhalis, pseudomonas, legionella, haemophilus influenzae, chlamydia, mycobacteria

Question 6

fluoroquinolones are effctive in ___________ but not __________.

Answer 6

gonorrhoea but not syphilis

Question 7

which fluoroquinolones has activity against streptococcus pneumoniae

Answer 7

levofloxacin

Question 8

which fluoroquinolone is used to reduce the incidence of post surgical UTI

Answer 8

levofloxacin

Question 9

2nd gen fluoroquinolones are addtionally active against which atypical organisms?

Answer 9

chlamydia/mycoplasma pneumoniae

Question 10

1st gen fluoroquinolones use is restricted to ttt of?

Answer 10

uncomplicated UTI

Question 11

what are the therapeutic indications of ciprofloxacin

Answer 11

prophylaxis against G- in nuetropenic patients
w aminoglycosides for ttt of febrile neutropenia
meningitis prophylaxis and carrier (hajj season)
for multi drug resistant TB

Question 12

name the most commonly used fluoroquinolone

Answer 12

ciprofloxacin

Question 13

typical therapeutic applications of ciprofloxacin

Answer 13

respiratory infections, UTI, gastric infections, anthrax, gonorrhea

Question 14

norfloxacin is used to treat?

Answer 14

complicated and uncomplicated UTI and prostatitis

Question 15

is norfloxacin used to treat systemic infections. why?

Answer 15

No because it is only concentrated in the urine

Question 16

uses of levofloxacin

Answer 16

prostatitis due to ecoli and STD

Question 17

which STD is levofloxacin not effective against

Answer 17

syphilis

Question 18

levofloxacin has excellent activity against

a. respiratory infections
b. syphilis
c. diarhhea

Answer 18

respiratory infections due to streptoccocus penumoniae

Question 19

what are the reasons for resistance of fluoroquinolones

Answer 19

altered target : mutations in DNa gyrase and topoisomerase IV
decreased accumulation : decreased porins and decreased drug (efflux pump)

Question 20

the absoprtion of fluoroquinolones is decreased by

Answer 20

antacids al3+ and mg2+

diet containing calcium and zinc

Question 21

fluoroquinolones accumulate in __________ and __________.

Answer 21

macrophages and leukocytes.

Question 22

the following is NOT an adverse reaction of fluoroquinolones

a. nephrotoxicity
b. phototoxicity
c. ototoxicty
d. CNS problems

Answer 22

c. ototoxicity

Question 23

caution must be taken with fluoroquinolones in CNS problems such as __________.

Answer 23

epilepsy

Question 24

name a drug that inteferes with th metabolism of fluoroquinolones

Answer 24

cimetidine

Question 25

ciprofloxacin and ofloxacin inhibit the metabolism of which 2 drugs

Answer 25

theophylline and warfarin

Question 26

Microorganisms commonly complicating UTI include:

Answer 26

E. coli (80% of cases)
Staphylococcus saprophyticus
Klebsiella pneumoniae
Proteus mirabilis

Question 27

urinary tract antiseptics achieve concentrated levels in the systemic circulation. t/f

Answer 27

false. they concentrate only in the urine

Question 28

in methenamine decomposition to __________ occurs at ____ pH.

Answer 28

formaldehyde, low pH

Question 29

methenamine is used to treat _______ but not _______.

Answer 29

lower UTI but not upper UTI

Question 30

methenamine is

a. bacteriostatic
b. bactericidal

Answer 30

a. bacteriostatic

Question 31

how can the effect of methenamine be increased

Answer 31

Higher activity in acidic urine, ascorobic acid and cranberry can be given to lower urine pH

Question 32

methenamine is contraindicated in

Answer 32

renal insufficiency

Question 33

what is the MOA of nitrofurantoin

Answer 33

susceptible bacteria reduce it to an acive agent that inhibits enzymes and damages DNA

Question 34

nitrofurantoin is
methenamine is
a. bacteriostatic
b. bactericidal

Answer 34

a. bacteriostatic

Question 35

adverse effects of nitrofurantoin and methenamine

Answer 35

nitrofurantoin 
GI disturbances 
hemolytic anemia in G6PD 
neurological problems 
methenamine : albuminuria, hematuria, GI disturbances