Fosfomycin Tromethamine

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Cat Number

API0231625

CAS Number

78964-85-9

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Product Detail Description Scientific Support Customer Q&A

CAS Number

78964-85-9

EINECS

279-018-8

Storage

Store at 2-8℃

Synonyms

Fosfomycin trometamol salt; 7FXW6U30GY; Z 1282; Fosfomycin compound with Trometamol; (1R,2S)-(1,2-Epoxypropyl)phosphonic Acid, compound with 2-Amino-2-(hydroxymethyl)-1,3-propanediol(1:1)

Molecular Formula

C7H18NO7P

Molecular Weight

259.19

Smiles

C[C@H]1[C@H](O1)P(=O)(O)O.C(C(CO)(CO)N)O

Appearance

White to off-white hygroscopic powder

General Description

Fosfomycin tromethamine is a broad-spectrum phosphonic acid antibiotic administered as a single oral dose for uncomplicated urinary tract infections. The tromethamine salt enhances water solubility and gastrointestinal absorption.

Mechanism of Action

Fosfomycin irreversibly inhibits the bacterial enzyme MurA (UDP-N-acetylglucosamine enolpyruvyl transferase), blocking the first step of peptidoglycan synthesis. This disrupts cell wall formation, leading to bacterial lysis. The drug penetrates well into the urinary tract and has activity against many multidrug-resistant organisms, including extended-spectrum beta-lactamase (ESBL)-producing E. coli and vancomycin-resistant enterococci (VRE). Resistance is rare due to the unique mechanism.

Application

Fosfomycin tromethamine is indicated for uncomplicated lower urinary tract infections (acute cystitis) in women caused by Escherichia coli and Enterococcus faecalis. A single 3-gram dose achieves therapeutic urinary concentrations for 48-72 hours. It is particularly useful for patients with frequent recurrences, antibiotic allergies, or infections with resistant strains.

In a pragmatic open‑label trial (143 patients with bacteremic urinary tract infection from multidrug‑resistant E. coli), intravenous fosfomycin (4 g q6h) was compared with ceftriaxone or meropenem. Clinical and microbiological cure at 5–7 days post‑treatment was 68.6% for fosfomycin versus 78.1% for comparators (risk difference –9.4%, 1‑sided 95% CI –21.5 to ∞; P=0.10 for noninferiority). Adverse event‑related discontinuations were more frequent with fosfomycin (8.5% vs. 0%, P=0.006). Fosfomycin did not meet noninferiority, primarily due to tolerability issues, though it may have utility in selected patients.

Fig. 1 Patient Recruitment and Flow Through Study. (Sojo-Dorado J, et al., 2022)

References

Sojo-Dorado J, et al. Effectiveness of Fosfomycin for the Treatment of Multidrug-Resistant Escherichia coli Bacteremic Urinary Tract Infections: A Randomized Clinical Trial. JAMA Netw Open. 2022;5(1):e2137277.

Does Fosfomycin Tromethamine require refrigerated storage as an epoxide antibiotic?

Yes, it should be stored at 2-8°C. The epoxide ring is thermally labile; at room temperature, ring-opening degradation occurs, leading to loss of antibacterial activity.

Is Fosfomycin Tromethamine sensitive to moisture, and how is this prevented?

It is hygroscopic and readily absorbs moisture, which can promote epoxide hydrolysis. Our packaging includes moisture-barrier aluminum foil bags with desiccant.

What is the stability of Fosfomycin Tromethamine after reconstitution for oral solution?

Reconstituted solutions are stable for up to 7 days under refrigeration. We provide detailed in-use stability data for various diluents and storage conditions.

How is the impurity 1,2-propanediol (from epoxide opening) monitored?

This degradation product is quantified using a validated GC method, ensuring it remains within ICH limits throughout shelf life.