9.1 Sulfa

Question 1

Broadly speaking, what is the mechanism of sulfa drugs?

Answer 1

Prevent folate synthesis- which is necessary for nuclei acid production

Question 2

What are the 2 mechanisms sulfa drugs use?

Answer 2

Sulfamethoxazole mimic PABA –> competitively inhibits DHT synthetase

Trimethoprim (TMP) – analog of dihydrofolate –> DHF reductase

Question 3

What is the IV sulfa drug?

Answer 3

Trimethroprim – sulfamethoxazole

Question 4

What are the PO sulfa drugs?

Answer 4

Trimethroprim – sulfamethoxazole (TMP-SMZ)/Bactrim/Septra
Dapsone
Sulfisoxazole/erythromycin (Pediazole)

Question 5

What G+ coverage do Sulfa drugs have?

Answer 5

Strep
Staph
Listeria

Question 6

What G+ are NOT covered by Sulfa? Why?

Answer 6

Enterococcus- Can bring in folate from host

Question 7

What G- coverage do sulfa drugs have?

Answer 7

H. flu

Enterobacteriaceae

Question 8

What is Dapsone used for?

Answer 8

Leprosy/ mycobacterium leprae

Question 9

What are the common side effects of Sulfa?

Answer 9

GI effects
Fever
Rash (including Stevens-Johnson syndrome)
Leukopenia
Thrombocytopenia
Hepatitis
Hyperkalemia

Question 10

What are special risks with Dapsone?

Answer 10

Hemolysis

Methemoglobinemia = decreased ability of RBC to carry O2

Question 11

What was the first Quinilone?

Answer 11

Nalidixic acid

Question 12

What G+ coverage does Nalidixic acid have?

Answer 12

Staph aureus

Strep

Question 13

What G- coverage does Nalidixic acid have?

Answer 13

E. coli

Question 14

What is the mechanism of Nalidixic acid against G+/G-?

Answer 14

G+: Topoisomerase
G-: DNA gyrase
= both interfere with unwinding of DNA

Question 15

What are the IV quinolones?

Answer 15

-oxacin
Ciprofloxacin
Levofloxacin
Moxifloxacin

Question 16

What are the PO quinolones?

Answer 16

-oxacin
Ciprofloxacin 
Levofloxacin 
Moxifloxacin 
Gemifloxacin 
Ofloxacin

Question 17

How do bacteria become immune to quinilones?

Answer 17

Mutation of topoisomerase IV/gyrase

Overexpression of reflux pumps

Question 18

What is the spectrum for Quinilones?

Answer 18

G+ = strep, staph
G- = H. Flu, Enterobacteriacea, Neisseria
Anaerobic = Clostridia, Bacteroids
Atypical = Chlamydia, Mycoplasma, Legionella
Mycobacteria = TB, MAC, Mycobacterium leprae

Question 19

What does Cipro cover?

Answer 19

R1 = piperazine – enhance G- activity (similar to PCN)
Covers Pseudomonas
Weak G+ activity – Not to treat Strep Pneumo infection
Many atypical
Some mycobacteria

Question 20

What does Levofloxacine cover?

Answer 20

2x more potent than ofloxacin
Less active against G- than Cipro
Covers Pseudomonas
More active against G+ than Cipro
Ok for strep pneumo including PCN resistant

Question 21

What is the difference between cipro/levo?

Answer 21

Cipro- more G-, weaker G+, pseudomonas

Levo- More G+, weaker G-

Question 22

What do Moxifloxin and Gemifloxacin cover?

Answer 22

Enhance activity against strep pneumo including PCN resistant
Atypical
Less active against G- (i.e. pseudomonas)
Good coverage for anaerobes

Question 23

What populations are quinilones contraindicated with?

Answer 23

Peds

Pregnancy

Question 24

What are the SA of quinilones?

Answer 24

QT prolongation
Achilles rupture
\+ risk for C Diff
N/V/D, abd pain
Headache/dizzy
Rash