Monuril (Fosfomycin)

Fosfomycin, a phosphonic acid antibiotic, is used to treat infections of the urinary tract.

• Acute uncomplicated cystitis in women: single‑dose therapy that clears infection and relieves symptoms.
• Uncomplicated urinary tract infection: provides bacterial eradication in a single oral administration.
• Susceptible uropathogen infection: effective against strains of Escherichia coli, Enterococcus faecalis and other bacteria that cause urinary infections.

• Fosfomycin inhibits bacterial cell‑wall synthesis by covalently binding to the MurA enzyme (enolpyruvyl transferase), preventing the formation of N‑acetylmuramic acid, an essential precursor of peptidoglycan. This blockade halts peptidoglycan polymerisation, leading to bactericidal activity against a broad range of Gram‑positive and Gram‑negative organisms, including many uropathogens. The drug penetrates urinary tract tissues and achieves high concentrations in urine, sustaining its antibacterial effect throughout the dosing interval.

Fosfomycin may be associated with several adverse reactions, which are generally categorized by frequency and severity.

Common Side Effects

• Diarrhea: loose stools occurring during or after treatment.
• Nausea: feeling of sickness or urge to vomit.
• Abdominal discomfort: mild pain or cramping in the stomach area.
• Vomiting: expulsion of stomach contents.
• Headache: mild to moderate head pain.
• Flatulence: excess gas causing abdominal distension.

Serious or Rare Side Effects

• Allergic reactions: rash, itching, swelling, or anaphylaxis in susceptible individuals.
• Clostridioides difficile‑associated colitis: severe diarrhea due to intestinal flora disruption.
• Hepatic dysfunction: elevated liver enzymes or jaundice indicating liver involvement.

When prescribing Fosfomycin, clinicians should consider several safety aspects.

• Renal impairment: dose adjustment may be required in patients with reduced kidney function.
• Pregnancy: safety not established; use only if clearly needed after risk assessment.
• Breastfeeding: unknown safety; weigh potential benefits against risks.
• Drug interactions: avoid concomitant use with agents that may diminish absorption or increase toxicity.
• Allergy: discontinue immediately if hypersensitivity signs appear.
• Store at ambient temperature: keep below 25 °C, protect from moisture and light.

Fosfomycin can interact with other medicines, requiring attention to avoid reduced efficacy or increased toxicity.

Major Interactions (Avoid)

• Antacids containing aluminum or magnesium: may reduce fosfomycin absorption.
• Probenecid: can increase serum fosfomycin levels, raising risk of adverse effects.

Moderate Interactions (Monitor Closely)

• Warfarin: fosfomycin may potentiate anticoagulant effect; monitor INR.
• Oral contraceptives: possible reduction in hormonal efficacy; consider backup contraception.
• Other antibiotics (e.g., aminoglycosides): may have additive nephrotoxic potential.