Phosphonic Acid Antibiotic Pregnancy: eMC §4.6: only limited data on fosfomycin treatment during the 1st trimester (n=152) are available; these do not raise any safety signal for teratogenicity so far. Fosfomycin crosses the placenta. Animal studies do not indicate direct or indirect harmful effects with respect to reproductive toxicity. 'Monuril should only be used during pregnancy, if clearly necessary.' Breast-feeding: fosfomycin is excreted in human milk in low quantities; if clearly necessary, a single dose of oral fosfomycin can be used during breast-feeding. Fertility: no human data.

Fosfomycin

Brand names: Monuril

Fosfomycin is a broad-spectrum bactericidal antibiotic given as a single oral sachet of fosfomycin trometamol, used for uncomplicated lower urinary tract infection in women, including some caused by multidrug-resistant organisms such as ESBL-producing coliforms.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Acute, uncomplicated cystitis in women and female adolescents (>12 years of age): 3 g fosfomycin once (single dose)

Route: Oral — dissolve the sachet in a glass of water and take immediately after preparation. For acute uncomplicated cystitis it should be taken on an empty stomach (about 2-3 hours before or 2-3 hours after a meal), preferably before bedtime and after emptying the bladder

Frequency: Single dose

SOURCE: eMC UK SPC 'Monuril 3g granules for oral solution' §4.2, quoted verbatim. SECOND INDICATION (verbatim): 'Perioperative antibiotic prophylaxis for transrectal prostate biopsy: 3 g fosfomycin 3 hours prior to the procedure and 3 g fosfomycin 24 hours after the procedure.' RESTRICTIONS: use is not recommended in renal impairment with creatinine clearance < 10 ml/min. 'In general, urinary tract infections in male patients have to be considered as complicated UTIs for which this medicinal product is not indicated' (§4.4) — the cystitis indication in this SPC is for women and female adolescents over 12 years only. PAEDIATRIC: 'The safety and efficacy of Monuril in children aged below 12 years of age have not been established' and §4.4 states the medicine should not be used in that age group — verify any under-18 use against a children's formulary. PERSISTENT INFECTION: re-examine and re-evaluate the diagnosis, as persistence is often due to complicated UTI or resistant pathogens (e.g. Staphylococcus saprophyticus). EXCIPIENTS: contains sucrose (avoid in hereditary fructose intolerance, glucose-galactose malabsorption, sucrase-isomaltase insufficiency) and sulphites (may rarely cause severe hypersensitivity reactions and bronchospasm); less than 1 mmol sodium per sachet. US CROSS-CHECK: the US label for fosfomycin tromethamine granules gives 'one sachet' for women 18 years of age and older with uncomplicated urinary tract infection (acute cystitis), taken with or without food, mixed with 3 to 4 ounces of water — it does not carry the UK prostate-biopsy prophylaxis regimen. §4.5 of the SPC was truncated at the source-fetch limit.

Dose adjustments

Renal

eMC §4.2: 'Use of Monuril is not recommended in patients with renal impairment (creatinin clearance < 10 ml/min).' No graded dose reduction is given.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Diarrhoea, nausea, dyspepsia and abdominal pain — 'The most common adverse reactions following the single-dose administration of fosfomycin trometamol involve the gastrointestinal tract, mainly diarrhoea', usually self-limited and resolving spontaneously; vomiting also listed
Headache and dizziness
Vulvovaginitis
Rash, urticaria and pruritus; angioedema
Anaphylactic reactions including anaphylactic shock, and hypersensitivity; antibiotic-associated colitis (Clostridioides difficile-associated and pseudomembranous colitis) — NOTE: the §4.8 frequency table was flattened during fetch, so the frequency column for each individual reaction could not be reconstructed reliably; the clinician should read the table in the SPC

Interactions

Metoclopramide — concomitant administration lowers serum and urinary concentrations of fosfomycin and should be avoided; other medicinal products that increase gastrointestinal motility may produce similar effects
Food — may delay absorption with a consequent slight decrease in peak plasma levels and urinary concentrations; preferably take on an empty stomach or about 2-3 hours after meals
Oral anticoagulants — numerous cases of increased oral anticoagulant activity have been reported in patients receiving antibiotic therapy; INR monitoring is advised (SPC text truncated at the source-fetch limit)
Cimetidine — the US label states cimetidine does not affect the pharmacokinetics of fosfomycin when co-administered

Clinical monograph

How it works

It irreversibly inhibits MurA (UDP-N-acetylglucosamine enolpyruvyl transferase), blocking an early step in bacterial cell-wall peptidoglycan synthesis and so killing the organism.

Prescribing in practice

Confirm the diagnosis is uncomplicated lower UTI before use; efficacy depends on adequate urinary concentrations, so it is not appropriate for pyelonephritis or other upper/complicated urinary tract infection unless specifically advised.
Take on an empty stomach, ideally at bedtime after emptying the bladder, dissolved in water; for treatment courses a second sachet may be advised after an interval per the SPC.
Resistance and reduced activity occur with some organisms, so prescribe according to local susceptibility data and resistance patterns.

Monitoring

Routine laboratory monitoring is not required; review clinically and arrange urine culture if symptoms persist or recur.

Counselling the patient

Dissolve the whole sachet in a glass of cold water and drink immediately on an empty stomach, preferably before bed.
Return if symptoms do not settle within a few days or worsen.

Evidence & guidelines

Single-dose fosfomycin trometamol is recommended in NICE and UK antimicrobial guidance as an option for uncomplicated UTI, particularly where resistance limits other agents.

Reference: NICE NG109 (UTI in adults); PHE Antimicrobial Prescribing Guidelines; EUCAST resistance data; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Fosfomycin · Phosphonic acid antibiotic

Pathways