Nitrofurantoin Flashcards
What is the indication?
acute, uncomplicated lower UTI
Prevention or recurrent UTI
What is the spectrum of activity?
Active against most organisms that cause uncomplicated UTI
E. coli (g-negative)
S.saprophyticus (g-positve)
What is the mechanism of action?
Nitrofurantoin is metabolised (reduced) in bacterial cells by nitrofuran reductase.
Its active metabolite damages bacterial DNA and causes cell death (bactericidal). Bacteria with lower nitrofuran reductase activity are resistant to nitrofurantoin.
Nitrofurantoin requires concentration in the urine by renal excretion for therapeutic effect against UTIs; for the same reason, it is not useful for infections elsewhere in the body.
What organisms have resistance to Nitrofurantoin?
Some organisms that are less common causes of UTI (such as Klebsiella and Proteus species) have intrinsic resistance to nitrofurantoin.
Nitrofurantoin requires concentration in the urine by renal excretion for therapeutic effect against UTIs; for the same reason, it is not useful for infections elsewhere in the body.
What are important side effects?
-GI upset
-immediate and delayed allergic reaction
-dark yellow or drown urine
-less common but with prolonged use :
-chronic pulmonary reactions (including inflammation (pneumonitis) and fibrosis)
-hepatitis
-peripheral neuropathy
What effect could nitrofurantoin have on neonates and why does it occur?
-Haemolytic anaemia
-immature red blood cells are unable to mop up nitrofurantoin-stimulated superoxides, which damage red blood cells.
Who should NOT be prescribed nitrofurantoin?
-pregnant women towards term
-Babies< 3months
-G6PD deficiency
- renal impairment
Who should be prescribed with caution?
-long term prevention of UTI:
chronic use increases the risk of pulmonary, hepatic and neurological adverse effects
What are important interactions?
Drugs that cause peripheral neuropathy
amiodarone
isonaizid
metronidazole
phenytoin
What are dosages for indications?
Acute UTI - 50mg QDS
-100mg MR BD
Prevention of recurrent UTI- 50mg- 100mg orally nightly regularly or single dose after exposure to known trigger
Max urinary concentrations are achieved 2-4 hours after dosing.
What are patient counselling points and why?
Taken with food or milk to minimise GI effects
(No parenteral formulation)
What are monitoring requirements?
Monitor for safety with long-term
for unexplained/new symptoms that could indicate pulmonary and adverse effects
How long is the treatment for both indications?
3 days for acute
7 days for men and pregnant women
For recurrent review every 6 months
When would you not give nitrofurantoin as first line for UTI?
At term pregnancy
Complicated UTI
Pyelonephritis
What would you give when complicated UTIs?
IV
Penicillin (broad spectrum) with beta lactase inhibitor
Cephalosporins
quinoline with or without amino glycoside.
