Fosfomycin

Indications

Fosfomycin is used for: Uncomplicated urinary tract infections (acute cystitis), Prostatitis

Adult Dose

Oral Urinary Tract Infection (Acute Cystitis) Acute cystitis caused by E. coli, E. faecalis Women >18 years: 1 sachet (3 g) PO once Males >18 years: 1 sachet (3 g) every 2-3 days for 3 doses Prostatitis 3 g PO every 3 days for 21 days

Child Dose

Renal Dose

Renal impairment: No dosage adjustment needed.

Administration

Reconstitution: Oral powd: Dissolve the contents of a single-dose sachet containing 3 g of the drug in 90-120 ml (half cup) of water of water and stir to dissolve. Do not use hot water. This should be taken immediately after dissolving in water. Do not use hot water. Should be taken on an empty stomach. Take on an empty stomach 1 hr before or 2 hr after meals.

Contra Indications

Hypersensitivity to fosfomycin.

Precautions

Patient w/ cardiac insufficiency, HTN, hyperaldosteronism, hypernatraemia or pulmonary oedema. Renal impairment (IV). Pregnancy and lactation. Patient Counseling Certain adverse effects may occur which may impair ability to drive or operate machinery. Monitoring Parameters Monitor serum electrolyte levels and water balance; signs and symptoms of UTI. Do not use more than one single dose to treat a single episode of acute cystitis. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. Lactation: excreted in breast milk; not recommended

Pregnancy-Lactation

Pregnancy Category: B Lactation: excreted in breast milk; not recommended

Interactions

Additive or synergistic effect w/ β-lactam antibiotics (e.g. penicillin, ampicillin, cefazolin, carbapenems) and anti-staphylococcal agents (e.g. linezolid, quinupristin/dalfopristin, moxifloxacin). Reduced serum levels w/ drugs which increase GI motility (e.g. metoclopramide).

Adverse Effects

Side effects of Fosfomycin : 1-10% Anorexia, Diarrhea, Epigastric, Discomfort, Headache, Nausea, Rash, Vomiting <1% Dizziness, Drowsiness, Fatigue, Pruritus Potentially Fatal: Anaphylactic shock, antibiotic-associated colitis and pseudomembranous colitis.

Mechanism of Action

Fosfomycin is a phosphoenolpyruvate (PEP) analogue that irreversibly inhibits enolpyruvate transferase (MurA), which prevents peptidoglycan biosynthesis at an earlier site compared to β-lactams with no cross-resistance with other agents. Thus, it inhibits bacterial cell wall biogenesis & shows bactericidal effects.