Nitrofurans

Question 1

Nitrofurans and Fosfomycin

Answer 1

Nitrofurantoin
Fosfomycin

Both drugs have different structures and MOAs but similar uses

Retain >90% activity against E. coli and adequate coverage against other common community acquired urinary tract pathogens

Only for lower urinary tract infections (due to pharmacokinetic limitations)
Do not use for more severe infections (pyelonephritis and urosepsis)

IV Fosfomycin used in other countries for more severe GNR infections

Question 2

Nitrofurans and Fosfomycin MOA

Answer 2

Fosfomycin inhibits bacterial cell wall synthesis differently than beta lactams and glycopeptides preventing the production of the building blocks of peptidoglycan

MOA of nitrofurantoin not characterized

Question 3

Nitrofurans and Fosfomycin Spectrum

Answer 3

Good
E. coli
Staph saprophyticus

Moderate
Citrobacter
Klebsiella
Proteus
Enterococci
Pseudomonas and Serratia (Fosfomycin)

Poor
Acinetobacter

Question 4

Nitrofurans and Fosfomycin Adverse Effects

Answer 4

GI
Occasional N/V
Taking with food may decrease effect

Pulmonary
Nitro may cause one of two forms of serious pulmonary toxicity (very rare)
1. Acute pneumonitis manifesting as cough, fever, and dyspnea (resolved soon after discontinuation)
2. Chronic pulmonary fibrosis most commonly with prolonged therapy (recovery of lung function is limited after drug discontinuation)

Question 5

Nitrofurans and Fosfomycin Important Facts

Answer 5

Drugs require high concentrations for antimicrobial activity (only happens in lower urinary tract)
If CrCL <50, there may be insufficient accumulation in urine; avoid Nitro in these patients

Nitro comes in 2 forms
Macrodantin (crystalline form)- QID
Macrobid (crystalline/monohydrate)- BID

Fosfomycin- only available as powder that patient add to water before taking

Nitro- one study showed that can be used for 5 days instead of traditional 7 days
Fosfomycin- approved regimen for treatment of uncomplicated cystitis is a single dose

Question 6

Nitrofurans and Fosfomycin Good For

Answer 6

Treatment of uncomplicated cystitis in patients with adequate renal function (both drugs)

Prophylaxis against recurrent uncomplicated lower UTIs (Nitro)

Do not use in anything but cystitis