From the Guidelines
The recommended dose of nitrofurantoin for an uncomplicated urinary tract infection (UTI) is 100 mg taken orally every 12 hours for 5 days, as supported by the American College of Physicians guidelines 1. This recommendation is based on the best practice advice for the treatment of uncomplicated bacterial cystitis, which suggests that clinicians should prescribe short-course antibiotics with either nitrofurantoin for 5 days, trimethoprim–sulfamethoxazole (TMP–SMZ) for 3 days, or fosfomycin as a single dose. Some key points to consider when prescribing nitrofurantoin include:
- The macrocrystal formulation (Macrobid) can be taken as 100 mg twice daily for 5 days.
- For patients with reduced kidney function, dosage adjustment is necessary, and nitrofurantoin should be avoided in those with creatinine clearance below 30 ml/min as it won't achieve effective urinary concentrations.
- Nitrofurantoin works by damaging bacterial DNA and is effective against most common UTI pathogens including E. coli.
- It should be taken with food to minimize gastrointestinal side effects like nausea.
- Patients should complete the full course even if symptoms improve quickly, drink plenty of water during treatment, and be aware that nitrofurantoin may turn urine brown or yellow.
- This antibiotic is not recommended for upper urinary tract infections or systemic infections, as stated in the guidelines 1.
From the Research
Nitrofurantoin Dose for UTI
- The recommended dose of nitrofurantoin for an uncomplicated urinary tract infection (UTI) is not explicitly stated in all studies, but one study 2 used a dose of 100 mg four times daily for three days.
- Another study 3 compared the efficacy and tolerability of a single dose of 3 g fosfomycin trometamol with the conventional treatment of nitrofurantoin 50 mg four times daily for seven days.
- A review of international guidelines 4 found that the evidence base for nitrofurantoin dosing has been interpreted in different ways, and there is little direct evidence to support the recommended 3-day course of 100 mg twice daily in UK guidelines.
- A systematic review and meta-analysis 5 compared the efficacy and safety of fosfomycin versus nitrofurantoin for the treatment of uncomplicated lower urinary tract infection (UTI) in women, but did not specify the optimal dose of nitrofurantoin.
Efficacy of Nitrofurantoin
- A study 2 found that nitrofurantoin was significantly more effective than placebo in achieving bacteriological cure and symptomatic relief in women with uncomplicated UTI.
- Another study 6 found that nitrofurantoin had a high susceptibility rate in common UTI pathogens, with 95.6% of E. coli urine isolates susceptible to nitrofurantoin.
- A review 4 noted that 3 days of nitrofurantoin may be a useful intervention in a large group of patients, but clinical response should be expected to vary widely.