Fosfomycin Trometamol Powder for Oral Solution
Composition
Each sachet contains Fosfomycin Trometamol BP equivalent to Fosfomycin 3.0 g, with excipients q.s.
Pharmacology
Drug Class: Antibiotic (phosphonic acid derivative).
Fosfomycin exerts a bactericidal effect on proliferating pathogens by preventing enzymatic synthesis of the bacterial cell wall. It inhibits the first stage of intracellular bacterial cell wall synthesis by blocking peptidoglycan synthesis:
- Inhibition of cell wall synthesis: the bacterial cell wall, composed of peptidoglycan, provides structural support and maintains cell integrity.
- Inhibition of enzymes: fosfomycin enters bacterial cells and inhibits the enzyme MurA, essential for early peptidoglycan formation.
- Weakening of the cell wall: without proper peptidoglycan formation, the cell wall becomes structurally unstable.
- Cell lysis and death: the resulting internal pressure imbalance causes the bacterial cell to rupture.
Pharmacodynamics
- Broad antimicrobial spectrum, active against both Gram-positive and Gram-negative pathogens.
- Activity against problem organisms including MRSA, VRE, ESBL- and carbapenemase-producing Enterobacterales, and multidrug-resistant Pseudomonas aeruginosa.
- High activity against biofilms; synergistic or additive effects with other antibiotic classes.
- Reno-protective effect when combined with nephrotoxic drugs; clinical resistance to fosfomycin remains low.
Pharmacokinetics
- Absorption: rapid oral absorption of the trometamol salt with high bioavailability relative to fosfomycin calcium; achieves high urinary concentrations.
- Distribution: volume of distribution ~0.30 L/kg; negligible plasma protein binding; crosses the placenta with low levels in breast milk.
- Metabolism: not metabolised; no hepatic metabolism or enterohepatic circulation — considered safe in hepatic impairment.
- Elimination: primarily renal (glomerular filtration); 80–90% excreted unchanged in urine within 12 hours; ~50–60% cleared in the first 3–4 hours (if CrCl ≥40 mL/min); high urinary concentrations are achieved and sustained.
- Half-life: ~2 hours in healthy adults.
Indications
MultiBac Sachet is indicated for the treatment of acute uncomplicated lower urinary tract infections (acute cystitis) in women aged 18 years and older caused by susceptible Escherichia coli and Enterococcus faecalis.
MultiBac Sachet is not indicated for the treatment of pyelonephritis or perinephric abscess.
To reduce the development of drug-resistant bacteria and maintain effectiveness, MultiBac Sachet should be used only to treat infections proven or strongly suspected to be caused by susceptible bacteria. Culture and susceptibility information should guide therapy where available; in its absence, local epidemiology and susceptibility patterns may inform empiric selection.
Contraindications
Known hypersensitivity to fosfomycin or any excipient.
Precautions
- Patients with severe kidney disease may require dose adjustment.
- Contains sucrose — a consideration for diabetic patients.
- Only a single dose should be used to treat an episode of acute cystitis.
- Elderly patients may require dose adjustment based on kidney function; paediatric dosing depends on body weight and infection type.
- May be used in pregnant women under medical supervision, where considered safer than some alternative antibiotics.
- No dosage adjustment required in hepatic impairment.
Adverse Effects
- Common: mild gastrointestinal upset (nausea or diarrhoea), headache or dizziness, temporary changes in taste, vulvovaginal candidiasis in women.
Drug Interactions
Patients should avoid taking calcium supplements, antacids, or dairy products within 2–3 hours of the dose, as these may interfere with absorption.
Overdosage
There is no specific antidote for fosfomycin overdosage. Management is supportive; fosfomycin is dialysable, and haemodialysis may be considered in cases of significant overdose in patients with renal impairment.
Dosage and Administration
Dosage form: Powder for oral solution. Route: Oral, mixed with water.
- Standard adult dosing: one 3 g sachet dissolved in 3–4 ounces (approx. 90–120 ml) of cool water, taken as a single dose on an empty stomach, preferably at bedtime after emptying the bladder. Do not use hot water.
- Taking the medication on an empty stomach enhances absorption; dosing before sleep allows maximum bladder concentration overnight.
- Should be taken orally immediately after dissolution.
Storage
Store below 25°C and protect from light. Keep out of reach of children.
Presentation
1 × 8 g sachet (equivalent to 3 g fosfomycin). For single use only.