Clinical data
Trade names Monuril (Zambon SpA)
AHFS/ Monograph
MedlinePlus a697008
  • US: B (No risk in non-human studies)
    Routes of
    ATC code
    Legal status
    Legal status
    Pharmacokinetic data
    Bioavailability 30–37% (oral, fosfomycin tromethamine); varies with food intake
    Protein binding Nil
    Metabolism Nil
    Elimination half-life 5.7 hours (mean)
    Excretion Renal and fecal, unchanged
    CAS Number
    PubChem CID
    ECHA InfoCard 100.041.315
    Chemical and physical data
    Formula C3H7O4P
    Molar mass 138.059 g/mol
    3D model (JSmol)
    Melting point 94 °C (201 °F)

    Fosfomycin (also known as phosphomycin or phosphonomycin and the trade names Monurol and Monuril) is a broad-spectrum antibiotic[1] produced by certain Streptomyces species, although it can now be made by chemical synthesis.

    As a single dose, fosfomycin is more convenient than a multiple-dose therapy norfloxacin, for the same antibacterial efficacy.[2]


    Fosfomycin (originally known as phosphonomycin) was discovered in a joint effort of Merck and Co. and Spain's Compañía Española de Penicilina y Antibióticos (CEPA). It was first isolated by screening broth cultures of Streptomyces fradiae isolated from soil samples for the ability to cause formation of spheroplasts by growing bacteria. The discovery was described in a series of papers published in 1969.[3] CEPA began producing fosfomycin on an industrial scale in 1971 at its Aranjuez facility.[4]


    Fosfomycin is indicated in the treatment of urinary tract infections (UTIs), where it is usually administered as a single oral megadose.[5] Its use in combination with tobramycin to treat lung infections in patients with cystic fibrosis was also explored.[6][7]

    The drug is well tolerated and has a low incidence of harmful side effects.[5] However, development of bacterial resistance under therapy is a frequent occurrence and makes fosfomycin unsuitable for sustained therapy of severe infections. It is not recommended for children and those over 75 years old.[8]

    Additional uses have been proposed.[9] The global problem of advancing antimicrobial resistance has led to a renewed interest in its use more recently.[10]

    Mechanism of action

    Fosfomycin is bactericidal and inhibits bacterial cell wall biogenesis by inactivating the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase, also known as MurA.[11] This enzyme catalyzes the committed step in peptidoglycan biosynthesis, namely the ligation of phosphoenolpyruvate (PEP) to the 3'-hydroxyl group of UDP-N-acetylglucosamine. This pyruvate moiety provides the linker that bridges the glycan and peptide portion of peptidoglycan. Fosfomycin is a PEP analog that inhibits MurA by alkylating an active site cysteine residue (Cys 115 in the Escherichia coli enzyme).[12][13]

    Fosfomycin enters the bacterial cell through the glycerophosphate transporter.[14]

    Antibacterial spectrum and susceptibility

    The fosfomycin molecule has an epoxide or oxirane ring, which is highly strained and thus very reactive.

    Fosfomycin has broad antibacterial activity against both Gram-positive and Gram-negative pathogens, with useful activity against E. faecalis, E. coli, and various Gram-negatives such as Citrobacter and Proteus. Given a greater activity in a low-pH milieu, and predominant excretion in active form into the urine, fosfomycin has found use for the prophylaxis and treatment of UTIs caused by these uropathogens. Of note, activity against S. saprophyticus, Klebsiella, and Enterobacter is variable and should be confirmed by minimum inhibitory concentration testing. Activity against extended-spectrum β-lactamase-producing pathogens, notably ESBL-producing E. coli, is good to excellent, because the drug is not affected by cross-resistance issues. Existing clinical data support use in uncomplicated UTIs, caused by susceptible organisms. However, susceptibility break-points of 64 mg/l should not be applied for systemic infections.

    Biosynthetic gene cluster

    The complete fosfomycin biosynthetic gene cluster from Streptomyces fradiae has been cloned and sequenced and the heterologous production of fosfomycin in S. lividans has been achieved by Ryan Woodyer of the Huimin Zhao and Wilfred van der Donk research groups.[15]


    Mutations that inactivate the nonessential glycerophosphate transporter render bacteria resistant to fosfomycin.[16][17][18]

    Fosfomycin resistance enzymes

    Enzymes conferring resistance to fosfomycin have also been identified and are encoded both chromosomally and on plasmids.[19]

    Three related fosfomycin resistance enzymes (named FosA, FosB, and FosX) are members of the glyoxalase superfamily. These enzymes function by nucleophilic attack on carbon 1 of fosfomycin, which opens the epoxide ring and renders the drug ineffective. The enzymes differ by the identity of the nucleophile used in the reaction: glutathione for FosA, bacillithiol for FosB,[20][21] and water for FosX.[19] In general, FosA and FosX enzymes are produced by Gram-negative bacteria, whereas FosB is produced by Gram-positive bacteria.[19]

    FosC uses ATP and adds a phosphate group to fosfomycin, thus altering its properties and making the drug ineffective.[22]


    1. Grif K, Dierich MP, Pfaller K, Miglioli PA, Allerberger F (Aug 2001). "In vitro activity of fosfomycin in combination with various antistaphylococcal substances". The Journal of Antimicrobial Chemotherapy. 48 (2): 209–17. doi:10.1093/jac/48.2.209. PMID 11481290.
    2. de Jong Z, Pontonnier F, Plante P (1991). "Single-dose fosfomycin trometamol (Monuril) versus multiple-dose norfloxacin: results of a multicenter study in females with uncomplicated lower urinary tract infections". Urol. Int. 46 (4): 344–8. doi:10.1159/000282164. PMID 1926651.
    3. Silver, L.L. Rational approaches to antibiotic discovery: pre-genomic directed and phenotypic screening, 2.4.2 Screens for spheroplast formation. In: Thomas Dougherty, Michael J. Pucci, Antibiotic Discovery and Development. Chap. 2, p. 46.
    4. Encros About us: Our history. Archived 2011-09-14 at the Wayback Machine.
    5. 1 2 Patel SS, Balfour JA, Bryson HM (Apr 1997). "Fosfomycin tromethamine. A review of its antibacterial activity, pharmacokinetic properties and therapeutic efficacy as a single-dose oral treatment for acute uncomplicated lower urinary tract infections". Drugs. 53 (4): 637–656. doi:10.2165/00003495-199753040-00007. PMID 9098664.
    6. Trapnell BC, McColley SA, Kissner DG, Rolfe MW, Rosen JM, McKevitt M, Moorehead L, Montgomery AB, Geller DE (2012). "Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection". American Journal of Respiratory and Critical Care Medicine. 185 (2): 171–8. doi:10.1164/rccm.201105-0924OC. PMC 3361752. PMID 22095545.
    7. Clinical trial number NCT00794586 for "Study Evaluating Fosfomycin/Tobramycin for Inhalation in Cystic Fibrosis Patients With Pseudomonas Aeruginosa Lung Infection" at
    8. "MONURIL SACHETS 3G". Retrieved May 26, 2014.
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    12. Zhu, Jin-Yi; Yang, Yan; Han, Huijong; Betzi, Stephane; Olesen, Sanne H.; Marsilio, Frank; Schönbrunn, Ernst (2012-04-13). "Functional Consequence of Covalent Reaction of Phosphoenolpyruvate with UDP-N-acetylglucosamine 1-Carboxyvinyltransferase (MurA)". Journal of Biological Chemistry. 287 (16): 12657–12667. doi:10.1074/jbc.M112.342725. ISSN 0021-9258. PMC 3339971. PMID 22378791.
    13. Krekel, Florian; Samland, Anne K.; Macheroux, Peter; Amrhein, Nikolaus; Evans, Jeremy N. S. (October 2000). "Determination of the pKaValue of C115 in MurA (UDP-N-Acetylglucosamine Enolpyruvyltransferase) fromEnterobacter cloacae†". Biochemistry. 39 (41): 12671–12677. doi:10.1021/bi001310x. ISSN 0006-2960.
    14. Santoro A, Cappello AR, Madeo M, Martello E, Iacopetta D, Dolce V (Jul 2011). "Interaction of fosfomycin with the glycerol 3-phosphate transporter of Escherichia coli". Biochimica et Biophysica Acta. 1810 (12): 1323–1329. doi:10.1016/j.bbagen.2011.07.006. PMID 21791237.
    15. Woodyer RD, Shao Z, Thomas PM, Kelleher NL, Blodgett JA, Metcalf WW, van der Donk WA, Zhao H (Nov 2006). "Heterologous production of fosfomycin and identification of the minimal biosynthetic gene cluster". Chemistry & Biology. 13 (11): 1171–82. doi:10.1016/j.chembiol.2006.09.007. PMID 17113999.
    16. Navas J, León J, Arroyo M, García Lobo JM (1990). "Nucleotide sequence and intracellular location of the product of the fosfomycin resistance gene from transposon Tn2921". Antimicrobial Agents and Chemotherapy. 34 (10): 2016–8. doi:10.1128/AAC.34.10.2016. PMC 171982. PMID 1963292.
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    19. 1 2 3 Rigsby RE, Fillgrove KL, Beihoffer LA, Armstrong RN (2005). "Fosfomycin resistance proteins: a nexus of glutathione transferases and epoxide hydrolases in a metalloenzyme superfamily". Methods in Enzymology. Methods in Enzymology. 401: 367–379. doi:10.1016/S0076-6879(05)01023-2. ISBN 9780121828066. PMID 16399398.
    20. Sharma SV, Jothivasan VK, Newton GL, Upton H, Wakabayashi JI, Kane MG, Roberts AA, Rawat M, La Clair JJ, Hamilton CJ (Jul 2011). "Chemical and Chemoenzymatic syntheses of bacillithiol: a unique low-molecular-weight thiol amongst low G + C Gram-positive bacteria". Angewandte Chemie. 50 (31): 7101–7104. doi:10.1002/anie.201100196. PMID 21751306.
    21. Roberts AA, Sharma SV, Strankman AW, Duran SR, Rawat M, Hamilton CJ (Apr 2013). "Mechanistic studies of FosB: a divalent-metal-dependent bacillithiol-S-transferase that mediates fosfomycin resistance in Staphylococcus aureus". The Biochemical Journal. 451 (1): 69–79. doi:10.1042/BJ20121541. PMC 3960972. PMID 23256780.
    22. García P, Arca P, Evaristo Suárez J (Jul 1995). "Product of fosC, a gene from Pseudomonas syringae, mediates fosfomycin resistance by using ATP as cosubstrate". Antimicrobial Agents and Chemotherapy. 39 (7): 1569–73. doi:10.1128/aac.39.7.1569. PMC 162783. PMID 7492106.
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