How It Works
Fosfomycin works by disrupting the bacteria’s ability to build and maintain their protective cell walls. Without these walls, the bacteria cannot grow and eventually die.
| Quick Facts | |
|---|---|
| Common Brands | Monurol |
| Drug Class | Antibiotic |
| Generic Status | Generic is available |
| Availability | Prescription only |
Dosing
Fosfomycin is administered as a single oral dose of 3 grams. Mix the contents of one single-dose packet into 3 to 4 ounces of cool or cold water. Stir the solution well and consume it immediately.
To ensure the full 3-gram dose is ingested, add a small amount of water to the glass, swirl gently to capture any remaining powder, and drink the remaining liquid right away.
Note: Dosing information below is educational only. Your prescribing physician will determine your specific dose based on your individual health needs. Always follow your healthcare provider’s instructions for exact dosing.
Uses
FDA-Approved Uses
Fosfomycin is FDA-approved to treat uncomplicated urinary tract infections (UTIs) in women caused by Escherichia coli and Enterococcus faecalis strains of bacteria.
Off-Label Uses
You may see fosfomycin packets prescribed for uses that are not “FDA-approved.” This is a very common and legal practice called “off-label” prescribing, where a doctor uses their clinical judgment to prescribe a drug for a different (but well-researched) purpose.
Fosfomycin may be used off-label for treating uncomplicated UTIs and prostate infections in men.
Side Effects
Like all medications, fosfomycin packets can cause side effects. Some common side effects may improve over time as your body adjusts to the medication. Other side effects may be serious and require medical attention.
Common Side Effects
- Diarrhea
- Nausea
- Headache
- Upset stomach
- Vaginal pain, redness, swelling, or itching
- Dizziness
- Low energy
Serious Side Effects
Serious side effects are rare, but it’s important to know what to look for if they do occur. Stop using fosfomycin packets and call your doctor immediately if you experience:
- Severe allergic reactions: Symptoms include swelling of the face, lips, tongue, or throat (angioedema); difficulty breathing or swallowing; racing heart; severe rash or itching; and/or fever.
- Clostridioides difficile (C. diff) diarrhea: Antibiotics can alter the normal flora, increasing the risk of this severe bacterial infection. Symptoms include persistent or watery diarrhea, fever, blood in the stool, and severe stomach cramping. Symptoms may occur up to 2 months after you take fosfomycin.
Call your doctor immediately if you experience any concerning or prolonged symptoms.
Pharmacist Tips
Prepare Your Dose With Water
Never swallow the dry fosfomycin granules directly. Always mix the full packet with 3 to 4 ounces of cool or cold water.
Don’t Use Hot Water To Dissolve The Powder
Heat can degrade the medication and hinder its effectiveness in treating your infection.
Take Your Dose With Or Without Food
However, taking it with food may help minimize potential stomach-related side effects like nausea or diarrhea.
Wait 2–3 Days
UTI symptoms should generally begin to improve within a few days of taking the dose. If your symptoms persist beyond 3 or 4 days, or if they initially improve and then return, contact your healthcare provider for further evaluation.
Limit Or Avoid Alcohol
While there are no direct interactions between fosfomycin and alcohol, standard guidelines suggest avoiding drinking. Alcohol can suppress your immune response, making it harder for your body to fight the infection.
Store At Room Temperature
Fosfomycin packets should be stored at 68°F to 77°F (20°C to 25°C) in a cool, dry place away from light.
Tell Your Provider If You’re Pregnant Or Breastfeeding
Fosfomycin can be taken during pregnancy, but it is not known if the medication passes into breast milk. Tell your healthcare provider if you are pregnant, breastfeeding, or planning to be so that they can recommend the safest option for you.
Drug Interactions
Certain medications and substances can interact with fosfomycin packets, potentially altering how it works or increasing the risk of side effects. For example:
- Drugs that affect gastrointestinal motility: Fosfomycin can interact with medications that affect how quickly food and medicines move through your digestive system, such as metoclopramide (Reglan). If you are taking metoclopramide, your provider may recommend taking the medications at two different times to ensure the fosfomycin is fully absorbed.
Always give your doctor and pharmacist a complete list of all your medications, vitamins, and supplements to check for potential interactions.
FAQs
Why must fosfomycin granules be dissolved in water rather than swallowed dry?
Fosfomycin is a granulated powder that must be dissolved into a liquid oral solution to be safely ingested and absorbed by the body. Swallowing the medication dry is strictly advised against.
How much cold water is required to dissolve a fosfomycin sachet?
Standard guidelines suggest using approximately 3 to 4 ounces of cool or cold water, or about half a cup.
Should fosfomycin be taken on an empty stomach or with a meal?
Fosfomycin can be taken either on an empty stomach or with food. However, taking it with a meal might help reduce the likelihood of experiencing gastrointestinal-related side effects, such as nausea or diarrhea.
How long does fosfomycin take to relieve urinary tract infection symptoms?
Some people may begin to notice improvement within a few days, though response time can vary.
What is the medical protocol if urinary tract infection symptoms persist three days after taking fosfomycin?
If symptoms fail to improve by the third or fourth day — or if they worsen — contact your healthcare team. They may want to perform further testing to identify the specific bacteria causing the infection and determine whether you need a different type of antibiotic.
Is fosfomycin safe for patients with a penicillin or sulfa allergy?
Yes, fosfomycin is generally safe for individuals with penicillin or sulfa allergies. It is not a sulfa drug, nor is it related to penicillin. It belongs to an entirely different class of antibiotics. However, it’s always a good idea to share any allergies you have with your provider before starting a new medication.
Is fosfomycin approved for treating kidney infections?
No, fosfomycin is only approved for treating uncomplicated urinary tract infections in women. It is not suitable or approved for more severe complications, such as pyelonephritis (kidney infections), and should not be used for infections located outside of the bladder and urinary tract.
Is fosfomycin considered safe to take during pregnancy?
Yes, the American College of Obstetricians and Gynecologists considers fosfomycin a safe treatment option for most urinary tract infections during pregnancy. Pregnant people should still consult their healthcare provider to ensure it is the right choice for their specific situation.
Does the fosfomycin powder formulation contain sucrose or artificial sweeteners?
Yes, fosfomycin powder contains both sucrose and artificial sweeteners like saccharin as inactive ingredients. These are included to improve the taste.
Does fosfomycin interact with the efficacy of oral contraceptives?
Fosfomycin is not known to interact significantly with birth control pills. It is always recommended to share a full list of medications with your healthcare provider so they can check for possible interactions.
Comparable Medications
Fosfomycin packets, nitrofurantoin, Bactrim, ciprofloxacin, cephalexin, amoxicillin, or Macrobid?
There are several medications that your doctor can prescribe instead of fosfomycin packets. Here are a few possible alternatives below.
Nitrofurantoin
From $34.99
An oral antibiotic taken for 3 to 7 days to treat urinary tract infections (UTIs).
Bactrim
An oral antibiotic taken for 5 to 14 days to treat various bacterial infections, including UTIs, ear infections, bronchitis, and traveler’s diarrhea.
Ciprofloxacin UTI
From $39.99
An oral antibiotic taken for several days to treat bacterial infections like a UTI, or exposure to anthrax or plague.
Cephalexin Capsules (UTI)
From $41.99
An oral antibiotic taken for several days to treat various bacterial infections, including UTIs and skin, bone, or ear infections.
Amoxicillin Capsules
From $28.99
An oral penicillin antibiotic taken for several days to treat various bacterial infections, including UTIs, pneumonia, bronchitis, and tonsillitis.
Macrobid
An oral antibiotic taken for 7 days to treat urinary tract infections (UTIs).
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Important: Information on this page is for educational purposes only. Prescribing decisions are made by independent, licensed providers. TelyRx operates technology-enabled pharmacies and a telehealth platform that connects patients with licensed providers. Prescriptions, when provider-approved and issued, are filled and shipped by TelyRx-affiliated pharmacies. We do not employ physicians or make prescribing decisions. Learn more about our editorial standards here.