Fosfomycin

Fosfomycin is a broad-spectrum antibiotic used specifically as a single-dose treatment for uncomplicated urinary tract infections (bladder infections). A single dose of 3 grams is enough to fight the infection.

The medication becomes highly concentrated in the urine, where it reaches bactericidal concentrations for several days.

Well-known brand names are Monuril® and generics.

Fosfomycin has a bactericidal effect through a unique mechanism:

Mechanism of action: Fosfomycin inhibits the enzyme MurA (pyruvyl transferase), which is required for the first step of bacterial cell wall synthesis. Without a functional cell wall, the bacteria burst.

Special features:

• Unique mechanism of action – cross-resistance with other antibiotic classes is not known
• Very good urine concentrations (bactericidal for up to 48-72 hours)
• Effective against the most common pathogens that cause urinary tract infections
• Low development of resistance

Spectrum of activity:

• Escherichia coli (most common pathogen causing bladder infections)
• Enterobacter
• Klebsiella
• Enterococci
• Proteus

Fosfomycin is suitable for:

• Women with uncomplicated acute cystitis (bladder infection)
• As a single-dose treatment for typical symptoms
• For a first or infrequent occurrence

Typical symptoms:

• Burning when urinating
• Frequent urge to urinate
• Little urine despite the urge
• Lower abdominal pain

Not suitable for:

• Complicated urinary tract infection
• Kidney infection (pyelonephritis)
• Men (different treatment needed)
• Children under 12 years of age
• Severe renal impairment

Standard dosage:

• 3 g fosfomycin trometamol as a single dose

Dosage form:

• Granules for oral solution
• Sachet containing 3 g fosfomycin

For recurrent infections: A repeat dose is not intended, as fosfomycin is used as a single dose. If the infection persists, a thorough medical examination and re-evaluation of the diagnosis are recommended.

Preparation: 1. Dissolve the contents of the sachet in a glass of water (not hot) 2. Stir until dissolved 3. Drink immediately

Timing:

• Ideally in the evening before going to bed
• On an empty stomach (2-3 hours after eating)
• Or in the morning after getting up (2-3 hours before breakfast)

Why on an empty stomach? Food slows absorption and can reduce the concentration in the urine.

After taking it:

• Drink plenty of fluids to flush the bladder
• Symptoms may persist for another 2-3 days
• See a doctor if your condition worsens or you develop a fever

Fosfomycin must not be taken in cases of:

• Hypersensitivity to fosfomycin
• Severe renal impairment (creatinine clearance <10 ml/min)
• Hemodialysis

Not suitable for treatment in:

• Complicated urinary tract infection
• Kidney infection
• Men
• Children under 12 years of age

Pregnancy: Can be used if there is an appropriate indication. There is no evidence of harm. Decision on a case-by-case basis.

Breastfeeding: Fosfomycin passes into breast milk. With a single dose, consider a short break from breastfeeding.

Common (1-10%):

• Diarrhea
• Nausea
• Headache
• Dizziness

Uncommon (0.1-1%):

• Vomiting
• Abdominal pain
• Vaginal yeast infection
• Skin rash

Rare:

• Allergic reactions
• Elevated liver enzymes

Note: The side effects are usually mild and temporary. Diarrhea is the most common side effect.

Absorption reduced by:

• Metoclopramide – can speed up gastric emptying
• Food – so take it on an empty stomach

No clinically relevant interactions with:

• Hormonal contraception
• Most other medications

Caution: Regular monitoring of kidney function when other nephrotoxic medications are taken at the same time.