Fosfomycin

Fosfomycin 3 g Sachet (Granules for Oral Solution)

Fosfomycin (fosfomycin tromethamine) is a single-dose oral antibiotic supplied as granules for oral solution. In Canadian product information, it is indicated only for uncomplicated urinary tract infection (acute cystitis) in women caused by susceptible strains of Escherichia coli and Enterococcus faecalis. It is not indicated for pyelonephritis (kidney infection) or perinephric abscess.

Dosage and Directions

Adults (women 18 years of age and older): one sachet (3 g) taken as a single dose. It can be taken with or without food.

How to take: Pour the entire contents of the sachet into 3 to 4 ounces of water (1/2 cup) and stir until dissolved. Do not use hot water. Take it right away after dissolving. Do not take it dry.

Your symptoms should improve within about 2 to 3 days. If they do not, contact your health care provider.

Precautions

• Do not use more than one single dose to treat one episode of acute cystitis. Repeated daily doses did not improve outcomes and increased side effects.
• Antibiotic-associated diarrhea: diarrhea can happen with antibiotics. Get medical advice right away if you develop watery or bloody stools, with or without stomach cramps and fever, even up to 2 months after taking the dose.
• Pregnancy: use during pregnancy only if clearly needed. Breastfeeding: it is not known whether fosfomycin tromethamine passes into human milk; discuss feeding options with your provider.
• Pediatrics: safety and effectiveness in children 12 years and under have not been established.

Contraindications

Do not use if you have a known hypersensitivity to fosfomycin.

Drug Interactions

• Metoclopramide (and other drugs that increase gastrointestinal motility) may lower serum concentrations and urinary excretion of fosfomycin.
• Cimetidine does not affect fosfomycin pharmacokinetics when taken at the same time.

Possible Side Effects

In clinical studies, the most common drug-related side effects (>1%) were diarrhea, vaginitis, nausea, headache, dizziness, asthenia, and dyspepsia. Other events reported in clinical trials included rhinitis, back pain, dysmenorrhea, pharyngitis, abdominal pain, rash, and temporary lab changes.

Rare serious side effects have been reported after marketing (mostly outside the United States), including angioedema, aplastic anemia, worsening asthma, cholestatic jaundice, hepatic necrosis, and toxic megacolon; during post-marketing surveillance, anaphylaxis and hearing loss have also occurred.

Missed Dose

This product is taken as a single dose. If you forget to take it, take it as soon as you remember on the same day. Do not take an extra sachet to make up for a missed dose; contact your prescriber for advice.

Overdose

Events seen in patients who took too much fosfomycin include vestibular loss, impaired hearing, metallic taste, and a general decline in taste perception. In the event of an overdose, treatment should be symptomatic and supportive. Seek urgent medical help if an overdose is suspected.

Storage

Store at 25°C (77°F); excursions permitted to 15-30°C (59-86°F). Keep out of reach of children.