Folic Acid Synthesis Inhibitors/Fluorquinolones

Question 1

the combination of these two drugs causes a sequential blockade of folic acid synthesis.

Answer 1

sulfonamide with trimethoprim (both antifolate drugs)

Question 2

what is the mechanism of action of fluoroquinolones?

Answer 2

to selectively inhibit microbial nucleic acid metabolism

Question 3

how does sulfonamide differ from trimethoprim in MOA?

Answer 3

sulfonamides inhibit microbial enzymes involved in folic acid synthesis (compete with PABA and inhibit dihydropteroate synthase) while trimethoprim is a selective inhibitor of dihydrofolate reductase

Question 4

what is the purpose of using a combination of 3 separate sulfonamides (triple sulfa)?

Answer 4

to reduce the likelihood that any one drug will precipitate (this due to the fact that solubility may be decreased in acidic urine)

Question 5

place the sulfonamides in order from longest to shortest acting: sulfamethoxazole, sulfisoxazole, and sulfadoxine.

Answer 5

sulfadoxine, sulfamethoxazole, and sulfisoxazole.

Question 6

what is the reason why trimethoprim reaches high concentrations in prostatic and vaginal fluids?

Answer 6

b/c it is a weak base that gets trapped in acidic environments

Question 7

by blocking dihydrofolate reductase, what exactly is trimethoprim doing?

Answer 7

preventing the formation of tetrahydrofolic acid (active tetrahedron form of folic acid)

Question 8

true or false: sulfonamides are active against only gram + bacteria

Answer 8

false; both gram - and gram + bacteria

Question 9

for UTIts what is the preferred route of administration of sulfonamides?

Answer 9

oral

Question 10

for ocular infections what is the preferred route of administration of sulfonamides?

Answer 10

topical

Question 11

for burns, what is the preferred route of administration of sulfonamides?

Answer 11

topical

Question 12

for ulcerative colitis or RA what is the preferred route of administration of sulfonamides?

Answer 12

oral

Question 13

what is the 3 agent regimen for the treatment of toxoplasmosis involving sulfonamides?

Answer 13

sulfadizine, pyrimethamine (dihydrofolate reductase inhibitor) and folinic acid

Question 14

what is the DOC for the prevention and tx of pneumocystis pneumonia?

Answer 14

TMP-SMZ -Trimethoprim/sulfamethoxazole

Question 15

what is the reason why sulfonamides can cause crystalluria and hematuria?

Answer 15

precipitation in the urine at acidic pH

Question 16

what are two common drug interactions that are known to occur with sulfonamides due to competition for plasma protein binding?

Answer 16

warfarin and methotrexate - the result is an increase in plasma levels for both drugs

Question 17

how are fluoroquinolones classified?

Answer 17

by generation

Question 18

as fluoroquinolones increase in generation number, what happens to their coverage against gram + bacteria?

Answer 18

increases

Question 19

third gen fluoroquinolones are commonly referred to as what?

Answer 19

respiratory fluoroquinolones

Question 20

this is a 1st generation fluoroquinolone derived from nalidixic acid and has activity against common pathogens that cause UTIs

Answer 20

Norfloxacin

Question 21

to which generation do the following drugs belong? levofloxacin, gemifloxacin, and moxifloxacin

Answer 21

3rd

Question 22

to which generation do the following drugs belong? ciprofloxacin and ofloxacin

Answer 22

2nd

Question 23

what is the MOA used by fluoroquinolones to interfere with bacterial DNA synthesis? (in both gram - and gram + bacteria)

Answer 23

inhibit topoisomerase II (DNA gyrase) in gram - and topoisomerase IV in gram +
IOW they block the relaxation of supercoiled DNA which is necessary for transcription and translation

Question 24

true or false: fluoroquinolones exhibit a postantibiotic effect much like amino glycosides.

Answer 24

true

Question 25

which two fluoroquinolones have the widest spectrum of activity?

Answer 25

gemifloxacin and moxifloxacin

Question 26

what is the most common adverse effect of the use of fluoroquinolones?

Answer 26

GI distress

Question 27

the use of fluoroquinolones is prohibited in which two patient populations? why?

Answer 27

pregnant women and children due to its ability to damage growing cartilage and cause arthropathy

Question 28

newer fluoroquinolones have what manifestations on the EKG?

Answer 28

prnlonged QTc