Fosfomycin – Single-dose antibiotic for uncomplicated urinary tract infections.
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What is Fosfomycin?
Fosfomycin is a unique single-dose antibiotic that provides excellent convenience and effectiveness for uncomplicated urinary tract infections. Its distinct mechanism of action makes it particularly valuable for UTIs caused by resistant bacteria and for patients who prefer shorter treatment courses.
Book an online consultation if you’re experiencing UTI symptoms such as burning urination, frequent urination, or pelvic discomfort, especially if you’ve had previous UTIs or antibiotic treatments. Our GPs can assess your symptoms and determine if Fosfomycin or other UTI treatments are appropriate for your specific condition.
What is Fosfomycin used for?
- Uncomplicated urinary tract infections (UTIs)
- Acute cystitis in women
- UTIs caused by multi-drug resistant bacteria
- Recurrent UTI prevention (in some cases)
- UTIs in pregnancy (under specialist supervision)
- Lower urinary tract infections
How does Fosfomycin work?
A unique phosphonic acid antibiotic that inhibits bacterial cell wall synthesis by blocking an early step in peptidoglycan formation, with activity against both gram-positive and gram-negative bacteria.
Dosage and Administration
Adults
Single dose of 3g powder dissolved in water, taken on an empty stomach. Can be repeated once after 2-3 days if symptoms persist.
Children
Not routinely used in children—specialist supervision required.
Important Notes
- Mix powder with half a glass of cold water and drink immediately.
- Take on an empty stomach, preferably before bedtime after emptying bladder.
- Avoid food for 2-3 hours before and after taking.
- Usually only one dose needed for uncomplicated UTIs.
Side Effects
Common Side Effects
- Nausea and vomiting
- Diarrhoea
- Headache
- Dizziness
- Stomach upset
- Vaginal thrush (in women)
Serious Side Effects
Seek immediate medical attention if you experience:
- Severe allergic reactions
- Severe diarrhoea (C. difficile infection)
- Liver problems (rare)
- Blood disorders (very rare)
Important Warnings
- Tell your GP if you have kidney problems—dose adjustment may be needed.
- Not suitable for complicated UTIs or kidney infections.
- Complete emptying of bladder before taking improves effectiveness.
- Contact GP if symptoms don't improve within 2-3 days.
- Generally well tolerated with minimal drug interactions.
Drug Interactions
Tell your GP if you're taking any of the following medications:
- Metoclopramide—may reduce fosfomycin absorption.
- Generally fewer drug interactions than most antibiotics.
- Safe to use with most other medications.
- Does not significantly interact with oral contraceptives.
Frequently Asked Questions
How is a single dose of Fosfomycin as effective as a 3-7 day course of other antibiotics?
Fosfomycin concentrates very highly in urine and maintains effective levels for several days after a single dose, making it as effective as longer courses.
Why do I need to take it on an empty stomach?
Food significantly reduces the absorption of Fosfomycin, so taking it on an empty stomach ensures maximum effectiveness.
Can I take Fosfomycin for kidney infections?
No, it's only for uncomplicated lower urinary tract infections (cystitis). Kidney infections need different antibiotics and longer treatment.
Is Fosfomycin effective against antibiotic-resistant bacteria?
Yes, it has a unique mechanism of action that works against many bacteria resistant to other antibiotics, making it valuable for difficult-to-treat UTIs.
Medically Reviewed by: Mohammed Hassan - Independent Prescriber
Last Updated: 2025-01-14