(fos foe MYE sin)

U.S. Brand Names



Fosfomycin Tromethamine

Generic Available


Canadian Brand Names



Single oral dose in the treatment of uncomplicated urinary tract infections in women due to susceptible strains of and ; may have an advantage over other agents since it maintains high concentration in the urine for up to 48 hours

E. coliEnterococcus

Use - Unlabeled/Investigational

Multiple doses have been investigated for complicated urinary tract infections in men

Pregnancy Risk Factor



Enters breast milk/not recommended

Adverse Reactions

1% to 10%:

Central nervous system: Headache (47%), dizziness (1%)

Dermatologic: Rash (1%)

Gastrointestinal: Diarrhea (2% to 10%), nausea (4%), epigastric discomfort (1%), abdominal pain

Genitourinary: Vaginitis

Neuromuscular & skeletal: Weakness (1%)

<1%: Anorexia, drowsiness, fatigue, paresthesia, pruritus, somnolence, vomiting

Postmarketing and/or case reports: Angioedema, aplastic anemia, cholestasis, hepatic necrosis, jaundice, optic neuritis, toxic megacolon


Symptomatic and supportive treatment is recommended in the event of an overdose.

Drug Interactions

Antacids or calcium salts may cause precipitate formation and decrease fosfomycin absorption

Metoclopramide: Increased gastrointestinal motility may lower fosfomycin tromethamine serum concentrations and urinary excretion. This drug interaction possibly could be extrapolated to other medications which increase gastrointestinal motility.


Store at 15°C to 30°C (59°F to 86°F)

Mechanism of Action

As a phosphonic acid derivative, fosfomycin inhibits bacterial wall synthesis (bactericidal) by inactivating the enzyme, pyruvyl transferase, which is critical in the synthesis of cell walls by bacteria; the tromethamine salt is preferable to the calcium salt due to its superior absorption


Absorption: Well absorbed

Distribution: Vd: 2 L/kg; high concentrations in urine; well into other tissues; crosses maximally into CSF with inflamed meninges

Protein binding: <3%

Bioavailability: 34% to 58%

Half-life elimination: 4-8 hours; Clcr<10 mL/minute: 50 hours

Time to peak, serum: 2 hours

Excretion: Urine (as unchanged drug); high urinary levels (100 mcg/mL) persist for >48 hours


Adults: Oral:

Female: Uncomplicated UTI: Single dose of 3 g in 4 oz of water


Complicated UTI (unlabeled): 3 g every 2-3 days for 3 doses

Prostatitis (unlabeled): 3 g every 3 days for a total of 21 days

Dosing adjustment in renal impairment: Decrease dose; 80% removed by dialysis, repeat dose after dialysis

Dosing adjustment in hepatic impairment: No dosage decrease needed


Always mix with water before ingesting; do not administer in its dry form; pour contents of envelope into 90-120 mL of water (not hot), stir to dissolve and take immediately

Monitoring Parameters

Signs and symptoms of urinary tract infection; urine culture plus sensitivity

Patient Education

May be taken with or without food; avoid use of antacids or calcium salts within 4 hours before or 2 hours after taking fosfomycin; contact your prescriber if signs of allergy develop; if symptoms do not improve after 2-3 days, contact your prescriber

Additional Information

Many gram-positive and gram-negative organisms such as staphylococci, pneumococci, , , , , spp, and some strains of , indole-negative , and are inhibited. , and anaerobic gram-negative cocci are resistant.

E. coliSalmonellaShigellaH. influenzaeNeisseriaP. aeruginosaProteusProvidenciaB. fragilis

Dental Health: Effects on Dental Treatment

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

No information available to require special precautions

Mental Health: Effects on Mental Status

May cause drowsiness

Mental Health: Effects on Psychiatric Treatment

None reported

Dosage Forms

Powder, as tromethamine: 3 g


Patel SS, Balfour JA, and Bryson HM, "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, 1997, 53(4):637-56.

Shrestha N, Amuh D, Goldman MP, et al, "Treatment of a Complicated Vancomycin-Resistant Enterococcal Urinary Tract Infection With Fosfomycin,"Infectious Diseases in Clinical Practice, 2000, 9:368-71.

International Brand Names

Afos® (RO); Faremicin® (IT); Fosfocil® (DO, GT, HN, MX, PA, SV); Fosfocil® [inj.] (DO, GT, HN, MX, PA, SV); Fosfocina® [caps./liqu.oral] (ES); Fosfocina® (EC); Fosfocina® [inj.] (ES); Fosfocine® (FR); Fosfocin® [inj.] (IT); Fosfocin® (IT); Fosfomycin Biochemie® (AT); Fosmicin® (ID, TH); Fosmicin-S® (JP); Francital® (IT); Infectofos® (DE); Ipamicina® (IT); Monural® (HU, RO, RU, YU); Monuril® (AT, BE, BR, CH, CO, DE, FR, GB, IT, LU, NL, PT); Monurol® (AR); Monurol™ (CA); Monurol® (CL, ES, FI, IL, MX); Solufos® [caps./liqu.oral] (ES); Solufos® [inj.] (ES); Ultramicina® (IT); Uniryle® (RO); Uridoz® (FR); Urizone® (ZA); Veramina® (AR)

Review Date: 1969-12-31 Reviewed By: Keywords: ,
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