What is the proper administration of Fosfomycin (Monurol)?

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DS

Dainyal Siddiqui, MD

Internal Medicine

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Manuel Jimenez, MD

Cardiology

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Franz Pierre-Louis, MD

Infectious Disease

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Last updated: April 3, 2025 • View editorial policy

From the Guidelines

Fosfomycin should be taken as a single dose, typically 3 grams of powder dissolved in 3-4 ounces (about half a cup) of cold water, as recommended by the most recent guidelines 1.

Key Points to Consider

  • The single-dose treatment is effective because the medication concentrates in the urinary tract for an extended period (up to 48 hours), allowing it to fight the infection with just one dose.
  • It is essential to stir the mixture well until completely dissolved and drink it immediately, avoiding the use of hot water as it can affect the medication's effectiveness.
  • Taking fosfomycin on an empty stomach, preferably in the evening after emptying your bladder and before going to bed, helps maximize the concentration of the antibiotic in your urinary tract.
  • If you're taking it for a urinary tract infection, complete the entire prescribed dose even if symptoms improve quickly.
  • Avoid taking other medications within 2-3 hours of fosfomycin as they may interfere with its absorption.

Rationale

The recommendation for a single dose of fosfomycin is based on the guidelines for the prevention, diagnosis, and management of urinary tract infections in pediatrics and adults, which provide a clear recommendation for the duration of treatment with fosfomycin (oral) as a single dose for adult cystitis 1.

Additional Considerations

  • Fosfomycin works by inhibiting bacterial cell wall synthesis, specifically targeting the enzyme that helps bacteria form their protective outer layer.
  • The medication is effective against a wide range of bacteria, including those that cause urinary tract infections.
  • It is essential to follow the recommended dosage and administration instructions to ensure the effectiveness of the treatment and minimize the risk of adverse effects.

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 Pour the entire contents of a single-dose sachet of fosfomycin tromethamine into 3 to 4 ounces of water (1/2 cup) and stir to dissolve. Do not use hot water. Fosfomycin tromethamine should be taken immediately after dissolving in water.

To take fosfomycin,

  • Mix one sachet of fosfomycin tromethamine granules for oral solution with 3 to 4 ounces of water (1/2 cup)
  • Stir to dissolve
  • Take immediately after dissolving in water
  • May be taken with or without food
  • Do not take in its dry form
  • Do not use hot water [2] [3]

From the Research

Dosage and Administration

  • Fosfomycin tromethamine is typically administered as a single dose of 3 g for the treatment of uncomplicated urinary tract infections (UTIs) 4, 5, 6.
  • This single-dose regimen has been shown to be as clinically effective as 7- to 10-day treatment regimens of standard agents such as nitrofurantoin, norfloxacin, and trimethoprim/sulfamethoxazole 5.
  • A single oral dose of fosfomycin trometamol 3 g achieves high concentrations in urine, making it an effective treatment option for UTIs 6.

Treatment Options

  • Fosfomycin tromethamine is an important option for the first-line empirical treatment of uncomplicated lower UTIs 6.
  • It is also recommended as a first-line empiric antibiotic therapy for acute uncomplicated bacterial cystitis in otherwise healthy adult nonpregnant females, along with nitrofurantoin and pivmecillinam 7.
  • Fosfomycin has good in vitro activity against common uropathogens, including Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, and Staphylococcus saprophyticus 6.

Safety and Tolerance

  • Fosfomycin tromethamine is well tolerated and appears safe for use during pregnancy 5, 6.
  • Gastrointestinal adverse events, such as diarrhea and nausea, are the most commonly reported side effects 6.
  • The single-dose regimen of fosfomycin tromethamine also offers quality-of-life advantages, such as enhanced compliance and convenience 5.

References

5
Research

Fosfomycin tromethamine: single-dose treatment of acute cystitis.

International journal of fertility and women's medicine, 1999

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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