Fosfomycin

MONUROL

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Pronunciation: fos-foe-MYE-sin

Fosfomycin ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Fosfomycin ballicule

What it isInhibitor of an early step in cell wall synthesis; uncomplicated cystitis.

Why this oneSingle oral dose treats cystitis, and it retains activity against many multidrug-resistant organisms.

What limits itConcentrates only in urine, so it is useless for pyelonephritis or systemic infection.

Pearls

First-line cystitis option alongside nitrofurantoin and TMP/SMX.
One 3 g sachet dissolved in water.

Fosfomycin molecular structure (skeletal formula) — Molecular structure: Fosfomycin

Fosfomycin prescription history

Animated chart of estimated U.S. prescriptions per year, Antibacterials (systemic) (1938–2026). Fosfomycin enters in 1997 (estimated).

FDA-approved for

uncomplicated urinary tract infection (1996)

Principal riskUrine only, so useless in pyelonephritis

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryUnknown / historical label unavailable

Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.

FDA label

Read the full label on DailyMed ↗

NO BOXED WARNINGS

FDA dosing	Population	Start	Target	Max
Uncomplicated UTI (acute cystitis)	Women ≥18 y	One 3 g sachet single dose	One 3 g sachet single dose	One 3 g sachet single dose

Renal Undefined

Hepatic Undefined

Single-dose therapy; do not use multiple doses to treat a single episode of acute cystitis.

Instructions

Take with or without food
Mix granules with water (about 3-4 oz) before ingesting; do not take dry

Available strengths

sol 3 g/packet
granules 3000 mg
powder 3000 mg
inj 6 g

Cautions

Single-dose therapy only; multiple doses not more effective
Diarrhea/Clostridioides difficile-associated diarrhea
Hypersensitivity reactions

Adverse reactions

Diarrhea
Vaginitis
Nausea
Headache
Dizziness
Asthenia
Dyspepsia

Pregnancy Crosses the placental barrier; not teratogenic in animal studies.

Lactation Undefined

Cost

Fosfomycin (MONUROL)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $/unit	CostPlus
3 g/packet	sol	per unit	$26.22/ea	offered

Generic entry2020

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Self-check

How many oral fosfomycin doses treat uncomplicated cystitis here?
One.
Why is oral fosfomycin unsuitable for pyelonephritis?
It concentrates only in urine.