No

Antibiotic, Miscellaneous

A single oral dose in the treatment of uncomplicated urinary tract infections in women due to susceptible strains of E. coli and Enterococcus; multiple doses have been investigated for complicated urinary tract infections in men; may have an advantage over other agents since it maintains high concentration in the urine for up to 48 hours

B

Breast-feeding/lactation: Milk concentration approximates 10% of plasma

>1%:

Central nervous system: Headache

Dermatologic: Rash

Gastrointestinal: Diarrhea (2% to 8%), nausea, vomiting, epigastric discomfort, anorexia

<1%: Dizziness, drowsiness, fatigue, pruritus

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

Decreased effect: 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.

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

Protein binding: Minimal (<3%)

Metabolism: None

Bioavailability: 34% to 58%

Half-life: 4-8 hours; prolonged in renal failure (50 hours with Cl_cr <10 mL/minute)

Time to peak serum concentration: 2 hours

Elimination: High urinary levels persist for >48 hours (100 mcg/mL); excreted unchanged

Adults: Urinary tract infections: Oral:

Male: 3 g once daily for 2-3 days for complicated urinary tract infections

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 give in its dry form; pour contents of envelope into 90-120 mL of water (not hot), stir to dissolve. Drink immediately after dissolving.

Signs and symptoms of urinary tract infection

May cause drowsiness

None reported

No information available to require special precautions

No effects or complications reported

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 physician if signs of allergy develop; if symptoms do not improve after 2-3 days, contact your healthcare provider

Powder, as tromethamine: 3 g, to be mixed in 4 oz of water

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.