What is the recommended dosage administration for Fosfomycin (Phosphomycin)?

From the Guidelines

Fosfomycin is recommended to be administered as a single 3-gram oral dose for uncomplicated urinary tract infections in adults, as supported by the American College of Physicians and the IDSA/European Society of Clinical Microbiology and Infectious Diseases guidelines 1. The medication should be taken with water on an empty stomach, preferably before bedtime and after emptying the bladder.

• The powder formulation should be dissolved completely in 3-4 ounces (90-120 mL) of cold water, stirred well, and consumed immediately.
• For complicated UTIs or certain resistant infections, some clinicians may recommend a second 3-gram dose taken 2-3 days after the first dose, though this is an off-label use. Fosfomycin achieves high urinary concentrations quickly and maintains therapeutic levels for 24-48 hours, which allows for the convenient single-dose regimen.
• The medication works by inhibiting bacterial cell wall synthesis through a unique mechanism different from other antibiotics, making it effective against many resistant organisms. Patients should be advised that fosfomycin may cause mild gastrointestinal side effects like diarrhea, nausea, or headache, but these are typically transient.
• Patients with severe renal impairment (creatinine clearance <10 mL/min) may require dosage adjustment, as noted in various guidelines and studies 1. However, the most recent and highest quality study, which is from 2021, recommends a single dose of fosfomycin 3g PO for uncomplicated urinary tract infections 1. This recommendation is also supported by other studies, including one from 2022, which recommends a single dose of fosfomycin 3g PO for uncomplicated urinary tract infections due to multidrug-resistant organisms 1. Therefore, based on the strongest and most recent evidence, a single 3-gram oral dose of fosfomycin is the recommended dosage administration for uncomplicated urinary tract infections in adults.

From the FDA Drug Label

The recommended dosage for women 18 years of age and older for uncomplicated urinary tract infection (acute cystitis) is one sachet of fosfomycin tromethamine granules for oral solution. Fosfomycin tromethamine granules for oral solution may be taken with or without food. Fosfomycin tromethamine granules for oral solution should not be taken in its dry form. Always mix fosfomycin tromethamine granules for oral solution with water before ingesting

The recommended dosage administration for Fosfomycin is:

• One sachet of fosfomycin tromethamine granules for oral solution for women 18 years of age and older with uncomplicated urinary tract infection (acute cystitis)
• May be taken with or without food
• Should be mixed with water before ingesting, and not taken in its dry form 2

From the Research

Dosage Administration for Fosfomycin

• The recommended dosage administration for Fosfomycin (Phosphomycin) is a single oral dose of 3g, as indicated in studies 3, 4, 5, 6, 7.
• This single-dose regimen has been shown to be effective in treating acute uncomplicated lower urinary tract infections, with high clinical and bacteriological cure rates 3, 4, 6, 7.
• The single-dose administration of Fosfomycin tromethamine achieves high concentrations in urine, with peak urinary concentrations occurring within 4 hours and remaining high for 24 to 48 hours 3.
• Fosfomycin tromethamine is well tolerated, with a low incidence of adverse events, mainly gastrointestinal symptoms that are transient, mild, and self-limiting 3, 4, 7.

Efficacy of Fosfomycin

• Fosfomycin has been shown to be effective against common uropathogens, including Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, and Staphylococcus saprophyticus 4, 5, 6.
• Comparative clinical trials have demonstrated that a single 3g dose of Fosfomycin tromethamine is as clinically effective as 7- to 10-day treatment regimens of standard agents such as nitrofurantoin, norfloxacin, and trimethoprim/sulfamethoxazole 3, 4, 6.
• Fosfomycin tromethamine has also been shown to be effective in pregnant women with asymptomatic bacteriuria and lower urinary tract infections 4.