What is the administration schedule for Fosfomycin (antibiotic) in a 2-dose regimen?

From the Guidelines

Fosfomycin should be given as a single 3-gram dose for uncomplicated urinary tract infections, as recommended by the IDSA/European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guideline 1. However, for complicated urinary tract infections that require extended treatment, fosfomycin can be given as two 3-gram doses, with the first dose taken immediately and the second dose taken 24-48 hours later. When administering fosfomycin, each sachet should be dissolved in 3-4 ounces of cold water, stirred well until dissolved, and consumed immediately on an empty stomach. For best results, take the medication at least 2-3 hours before or after meals. The two-dose regimen provides extended antimicrobial coverage while maintaining high urinary concentrations of the drug. Fosfomycin works by inhibiting bacterial cell wall synthesis through interference with the enzyme phosphoenolpyruvate transferase. This mechanism allows it to be effective against many multi-drug resistant organisms, including ESBL-producing bacteria. Patients should complete both doses even if symptoms improve after the first dose to ensure complete eradication of the infection and prevent recurrence. Some studies suggest that a single dose of fosfomycin 3g PO is recommended for uncomplicated urinary tract infections due to VRE 2, 3. However, the most recent and highest quality study recommends a single dose of fosfomycin for uncomplicated urinary tract infections 1. It's essential to follow the guidelines and recommendations from reputable sources, such as the IDSA and ESCMID, to ensure the best possible outcomes for patients. Key points to consider when administering fosfomycin include:

• Dissolve the sachet in cold water and consume immediately on an empty stomach
• Take the medication at least 2-3 hours before or after meals
• Complete the full course of treatment, even if symptoms improve after the first dose
• Fosfomycin is effective against many multi-drug resistant organisms, including ESBL-producing bacteria.

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. The FDA drug label does not answer the question.

From the Research

Fosfomycin Dosage

• Fosfomycin is typically administered as a single 3-g dose for the treatment of uncomplicated urinary tract infections (UTIs) 4, 5, 6.
• However, in some cases, a multiple-dose regimen may be recommended, such as two 3-g doses administered 72 hours apart 7.
• This multiple-dose regimen can provide adequate urinary concentrations of fosfomycin for a longer period, making it effective for 7 days 7.

Administration Timing

• The exact timing of the two doses of fosfomycin is crucial to maintain adequate urinary concentrations of the antibiotic 7.
• Administering two 3-g doses of fosfomycin trometamol 72 hours apart can provide urinary concentrations above the critical concentration of sensitivity for Escherichia coli for 161 hours 7.
• This regimen can be effective for the treatment of uncomplicated lower UTIs, especially in cases where a single dose may not be sufficient 7.

Efficacy and Safety

• Fosfomycin has been shown to be effective and safe for the treatment of uncomplicated UTIs, with clinical and bacteriological cure rates comparable to those of other antibiotics, such as nitrofurantoin 4, 5, 6.
• The incidence of adverse events with fosfomycin is generally low, with gastrointestinal adverse events, such as diarrhea and nausea, being the most common 4, 5, 6.