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Fosfomycin

Pronunciation

Pronunciation

(fos foe MYE sin)

Index Terms

  • Fosfomycin Tromethamine

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Packet, Oral:

Monurol: 3 g (1 ea, 3 ea [DSC]) [orange flavor]

Brand Names: U.S.

  • Monurol

Pharmacologic Category

  • Antibiotic, Miscellaneous

Pharmacology

As a phosphoric 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

Absorption

Rapidly absorbed

Distribution

Vd: 90 to 180 L

Excretion

Urine (38% as unchanged drug); feces (18% as unchanged drug)

Time to Peak

Serum: 2 hours; within 4 hours with high-fat meal

Half-Life Elimination

3 to 8 hours; CrCl <54 mL/minute: 50 hours

Protein Binding

None

Special Populations: Renal Function Impairment

Urinary excretion decreases to 11% in patients with CrCl 7 to 54 mL/minute.

Use: Labeled Indications

Uncomplicated urinary tract infections: Treatment of uncomplicated urinary tract infections (acute cystitis) in women due to susceptible strains of Escherichia coli and Enterococcus faecalis.

Limitations of use: Not indicated for the treatment of pyelonephritis or perinephric abscess. If persistence or reappearance of bacteriuria occurs after treatment with fosfomycin, other therapeutic agents should be selected.

Use: Unlabeled

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

Contraindications

Hypersensitivity to fosfomycin or any component of the formulation

Dosing: Adult

Urinary tract infections, uncomplicated: Oral: Females: Single dose of 3 g in 3 to 4 oz (90 to 120 mL) of water

Complicated UTI (off-label): Males: Oral: 3 g every 2 to 3 days for 3 doses (Neuner 2012; Pullukcu 2007)

Prostatitis (off-label): Males: Oral: 3 g every 3 days for a total of 21 days (Shrestha, 2000)

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Reconstitution

Pour contents of envelope into 3 to 4 oz (90 to 120 mL) of water (not hot), stir to dissolve, and take immediately.

Administration

Always mix with cool water before ingesting; do not administer in its dry form. May be administered without regard to meals.

Storage

Store at 25°C (77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F).

Drug Interactions

BCG (Intravesical): Antibiotics may diminish the therapeutic effect of BCG (Intravesical). Avoid combination

BCG Vaccine (Immunization): Antibiotics may diminish the therapeutic effect of BCG Vaccine (Immunization). Monitor therapy

Cholera Vaccine: Antibiotics may diminish the therapeutic effect of Cholera Vaccine. Avoid combination

Lactobacillus and Estriol: Antibiotics may diminish the therapeutic effect of Lactobacillus and Estriol. Monitor therapy

Sodium Picosulfate: Antibiotics may diminish the therapeutic effect of Sodium Picosulfate. Management: Consider using an alternative product for bowel cleansing prior to a colonoscopy in patients who have recently used or are concurrently using an antibiotic. Consider therapy modification

Typhoid Vaccine: Antibiotics may diminish the therapeutic effect of Typhoid Vaccine. Only the live attenuated Ty21a strain is affected. Management: Vaccination with live attenuated typhoid vaccine (Ty21a) should be avoided in patients being treated with systemic antibacterial agents. Use of this vaccine should be postponed until at least 3 days after cessation of antibacterial agents. Consider therapy modification

Adverse Reactions

1% to 10%:

Central nervous system: Headache (4% to 10%), pain (2%), dizziness (1% to 2%)

Dermatologic: Skin rash (1%)

Gastrointestinal: Diarrhea (9% to 10%), nausea (4% to 5%), abdominal pain (2%), dyspepsia (1% to 2%)

Genitourinary: Vaginitis (6% to 8%), dysmenorrhea (3%)

Neuromuscular & skeletal: Back pain (3%), weakness (1% to 2%)

Respiratory: Rhinitis (5%), pharyngitis (3%)

<1% (Limited to important or life-threatening): Abnormal stools, anaphylaxis, angioedema, anorexia, aplastic anemia, cholestatic jaundice, constipation, dermatological disease, drowsiness, dysuria, ear disease, exacerbation of asthma, fatigue, fever, flatulence, flu-like symptoms, hearing loss, hematuria, hepatic necrosis, increased serum ALT, insomnia, lymphadenopathy, menstrual disease, migraine, myalgia, nervousness, optic neuritis, paresthesia, pruritus, toxic megacolon, vomiting, xerostomia

Warnings/Precautions

Concerns related to adverse effects:

• Superinfection: Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea (CDAD) and pseudomembranous colitis; CDAD has been observed >2 months postantibiotic treatment.

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information

Monitoring Parameters

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

Pregnancy Risk Factor

B

Pregnancy Considerations

Adverse events have not been observed in animal reproduction studies. Fosfomycin crosses the placenta. Several studies have used a single dose therapy with fosfomycin for the treatment of asymptomatic bacteriuria in pregnant women (Reeves, 1992). However, when treatment is needed in pregnant women, an appropriate antibiotic with a 3 to 7 day regimen is currently recommended (Nicolle, 2005).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience headache, vaginitis, nausea, or diarrhea. Have patient report immediately to prescriber signs of Clostridium difficile (C. diff)-associated diarrhea (abdominal pain or cramps, severe diarrhea or watery stools, or bloody stools) (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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