Merck Manual

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Brian J. Werth

, PharmD,

  • University of Washington School of Pharmacy

Last full review/revision Jul 2020| Content last modified Jul 2020
Click here for the Professional Version
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Fosfomycin is an antibiotic that has a unique chemical structure. It is used mainly to treat bladder infections caused by Escherichia coli (E. coli) or Enterococcus faecalis. It is sometimes used to treat other infections when they are caused by bacteria resistant to other antibiotics.

Some bacteria have an outer covering (cell wall) that protects them. Fosfomycin works by preventing bacteria from forming this wall, resulting in death of the bacteria.



Common Uses

Some Side Effects

Bladder infections caused by Escherichia coli (E. coli) or Enterococcus faecalis

Infections caused by fosfomycin-susceptible bacteria that are resistant to other antibiotics, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci*

Nausea and diarrhea

* These infections require intravenous fosfomycin (not yet available in the United States).

Fosfomycin is usually well-tolerated but may cause nausea and diarrhea.

Use of Fosfomycin During Pregnancy and Breastfeeding

Fosfomycin should be used during pregnancy only when the benefits of treatment outweigh the risks. (See also Drug Use During Pregnancy.)

Whether use of fosfomycin during breastfeeding is safe is not known. (See also Drug Use During Breastfeeding.)

Drugs Mentioned In This Article

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