This editorial discusses fosfomycin trometamol, a newly available antibiotic in the UK for single-dose treatment of uncomplicated cystitis. Fosfomycin is a naturally occurring antibiotic discovered in 1969 that inhibits bacterial cell wall synthesis by blocking an early enzymatic step. The trometamol formulation offers improved water solubility and bioavailability compared to previous calcium salt versions. After oral administration of 3 grams, the drug achieves peak bladder urine concentrations around 2000 mg/L with a half-life of approximately 4 hours, maintaining inhibitory levels for about 48 hours against most urinary pathogens. The author reviews evidence that single high-dose therapy is effective for uncomplicated lower urinary tract infections, comparable to traditional multi-day courses. However, potential concerns include variable in vitro susceptibility depending on culture media composition, and documented plasmid-mediated resistance involving enzymic inactivation, particularly in Spain and other countries with extensive fosfomycin use. While single-dose therapy offers convenience, cost-effectiveness, and safety advantages, the author cautions against viewing it as a universal treatment approach, noting that three-day regimens with conventional doses offer similar benefits with additional assurance of continued therapy during symptom resolution.

Key findings

• Fosfomycin trometamol achieves sustained inhibitory bladder urine concentrations (≥2000 mg/L) for approximately 48 hours following a single 3-gram oral dose, making it suitable for single-dose cystitis treatment.
• In vitro susceptibility testing of fosfomycin is highly dependent on culture media composition, glucose-6-phosphate, pH, and other conditions, making standardization difficult.
• Plasmid-mediated fosfomycin resistance involving enzymic modification has been documented and is circulating in countries with extensive drug use, though chromosomal resistance mechanisms also exist.
• Single high-dose therapy for uncomplicated cystitis is effective and offers advantages in cost, convenience, and identifying patients requiring further investigation, but should not be considered universally applicable to all lower urinary tract infections.