TMP/SMX, Nitrofurantoin, Fosfomycin

Question 1

TMP/SMX
- Resistance Mechanism

Answer 1

• Overproduction of PABA
• Decrease affinity for dihydrofolate synthase for sulfonamide
• Decrease affinity for dihydrofolate reductase for trimethoprim
• Decrease cell permeability

Question 2

TMP/SMX
- Adverse Effects

Answer 2

• GI
• Hematologic
• Photosensitivity
• Maculopapular Rashes
• Hyperkalemia

Question 3

Sulfonamide Cross Reactivity

Answer 3

N4 aromatic amine
N1 substituted ring is the cause for allergic reaction
- Little risk of cross reactivity with Non-Sulfonamide antibiotics

Do not rechallenge a life threatening reaction

Question 4

IgE Antibodies and allergies

Answer 4

Are not indicative of an IgE immediate type reaction

Question 5

TMP/SMX
- Counseling

Answer 5

Inhibits CYP 2C9
- Increases Warfarin, Phenytoin

Question 6

Nitrofurantoin
- Resistance Mechanism

Answer 6

Is reduced by bacteria flavoproteins into reactive intermediates that alter bacteria ribosomes
- Stable to resistance

Question 7

Nitrofurantoin
- Adverse Effects

Answer 7

• GI
• Hepatotoxicity
• Hypersensitivity
• Hematologic
• Neurologic
• Urine Discoluration

Question 8

Nitrofurantoin
- Counseling

Answer 8

Interacts with Uricosuric Agents (Sulfinpyrazone, Probenecid)
- Decrease excretion
- Increase toxicity
- Decreases UTI treatment

Question 9

Fosfomycin
- Resistance Mechanism

Answer 9

• Develops in multiple doses but not often with one dose
• Decreases uptake into bacterial cell (Chromosomal)
• Catalytic conjugation with glutathione

Question 10

Fosfomycin
- Adverse Effects

Answer 10

• GI
• Hypernatremia (IV)

Question 11

Fosfomycin
- Counseling

Answer 11

Is generally well tolerated

Safe in pregnancy