Source: Health Products Regulatory Authority (ZA) Revision Year: 2023 Publisher: PHARMACARE LIMITED, Healthcare Park, Woodlands Drive, Woodmead, 2191
Category and Class: A 20.1.1 Broad & medium spectrum antibiotics
Pharmacotherapeutic group: Antibacterials for systemic use, other antibacterials.
ATC code: J01XX01
Fosfomycin trometamol is a broad-spectrum bactericidal antibiotic, derived from phosphonic acid with activity in the lower urinary tract.
The antibacterial activity of fosfomycin is due to an inhibition of bacterial cell wall synthesis. Its mechanism of action is inhibition of enol pyruvyl transferase, which catalyses the formation of nacetylmuramic acid from n-acetyl aminoglucose and phosphoenolpyruvate. N-acetylmuramic acid is required for the build-up of peptidoglycan, an essential component of the bacterial cell wall. Fosfomycin has a mainly bactericidal action.
Fosfomycin is active in vitro against species of Gram-positive and Gram-negative bacteria most frequently isolated in urinary tract infections (E. Coli, Proteus, Klebsiella, Enterobacter, Staphylococcus, Streptococcus). In vitro sensitivity does not necessarily imply in vivo efficacy.
Fosfomycin trometamol is an orally well-absorbed salt of fosfomycin. It usually provides therapeutic concentrations of the activity moiety in the urine for periods of thirty-six hours or more from a single dose.
These doses give peak plasma concentrations after 2 hours of 20 to 30 mcg/mL, serum half-life is largely independent of dose.
Fosfomycin is eliminated mainly unchanged through the kidneys and this results in very high peak urinary concentrations (approximately 3000 mg/L) within two to four hours. Therapeutic concentrations in urine are usually maintained for at least thirty-six hours. Food delays and reduces absorption of fosfomycin trometamol, resulting in reduced blood and urinary concentrations.
In patients with moderately reduced renal function (creatinine clearance <80 mL/min), including the physiological reduction in the elderly, the half-life of fosfomycin is prolonged but urinary concentration remains therapeutically adequate.
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