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Mannitol (ATC A06AD16) is an osmotic laxative and diuretic sugar alcohol used orally to treat constipation and parenterally to reduce intracranial and intraocular pressure and promote forced diuresis, and its use in breastfeeding is generally regarded as low risk when clinically necessary, although formal data on milk transfer are limited.medpedia.framar+7

Pharmacology and clinical use

Mannitol is a polyhydric alcohol (sugar alcohol) that acts as an osmotic agent in the gastrointestinal tract and renal tubules.wikipedia+1
Oral mannitol retains water in the intestinal lumen, softens stool, and accelerates bowel transit, while intravenous mannitol increases plasma osmolality, mobilises water from intracellular to extracellular compartments, and enhances urine flow.straightanursingstudent+3
Parenteral indications include reduction of intracranial pressure and brain mass, management of acute cerebral oedema, reduction of elevated intraocular pressure when other measures are ineffective, and promotion of diuresis in acute renal failure or toxic exposures.accessdata.fda+4

The ATC class A06AD16 groups mannitol preparations used primarily as osmotic laxatives within the broader category of drugs for constipation.bbfarma+1
Typical adult parenteral doses are in the range 0.25–2 g/kg per dose (up to around 50–100 g over 24 hours), with daily totals not exceeding approximately 2.9 g/kg, while oral doses in laxative products are lower and titrated to effect.medsafe+2

Toxicology and safety profile

Clinically important adverse effects of mannitol arise from rapid fluid shifts and osmotic diuresis and include nausea, vomiting, headache, confusion, tachycardia, electrolyte disturbances, and acute kidney injury.clevelandclinic+2
Excessive plasma osmolality or accumulation in renal failure may precipitate or worsen heart failure, pulmonary oedema, or intracranial complications, particularly if used in patients with pre‑existing cardiac disease.medpedia.framar+3
Serious toxic reactions comprise acute renal failure, hyper‑ or hyponatraemia, hypotension or shock from hypovolaemia, rebound increases in intracranial pressure, and hypersensitivity reactions including rash.cbg-meb+4

Mannitol is contraindicated in anuric acute renal failure, severe dehydration or hyperhydration, active intracranial haemorrhage (except during craniotomy), pulmonary oedema or severe heart failure, and in patients with known hypersensitivity to mannitol.straightanursingstudent+4
Obstruction of the urinary tract may predispose to retention and further renal damage and is therefore listed among contraindications in prescribing information.accessdata.fda+2
Careful monitoring of urine output, serum electrolytes, and serum osmolality is required during repeated intravenous dosing to avoid cumulative toxicity.clevelandclinic+2

Pharmacokinetics relevant to lactation

After intravenous administration, mannitol is distributed predominantly to extracellular fluid, is minimally metabolised, and is eliminated by glomerular filtration with a plasma half‑life of a few hours in patients with normal renal function.ncbi.nlm.nih+2
Oral bioavailability of mannitol is low (approximately 17%), and non‑absorbed fractions act locally in the gut to exert the laxative effect.breastfeeding-and-medication+1
Because mannitol is highly water‑soluble and of relatively low molecular weight, passage into breast milk is theoretically possible, but available guidance states that there are no direct quantitative human milk data.drugs+2

Regulatory documents for injectable mannitol consistently note that it is not known whether mannitol is excreted in human milk and recommend that caution be exercised when administering the drug to nursing mothers.g-standaard+3
Given its short half‑life and renal elimination, clinically significant accumulation in breast milk is unlikely after single or short‑term dosing in women with normal renal function.ncbi.nlm.nih+2

Lactation risk assessment

Evidence specific to mannitol during breastfeeding is sparse, and product labelling generally advises use only when clearly needed, with caution.drugs+3
Expert lactation resources dealing with imaging procedures note that mannitol used as an adjunct (e.g. for MRI or CT) has low oral bioavailability, with any milk transfer expected to be small and exposure to the infant further limited by poor gastrointestinal absorption.breastfeedingnetwork+1
On this basis, authoritative breastfeeding organisations consider a single intravenous dose of mannitol compatible with continued breastfeeding, and they do not recommend routine interruption of lactation.breastfeedingnetwork+1

For mothers receiving repeated high‑dose parenteral mannitol (e.g. intensive care for cerebral oedema), the theoretical infant risk stems more from maternal haemodynamic instability and the infant’s overall clinical context than from direct mannitol exposure via milk.ncbi.nlm.nih+2
If there is concern in complex cases, individual risk–benefit assessment—including the importance of breastfeeding, maternal renal function, and alternative therapies—is appropriate, and short, temporary milk expression and discarding for 12–24 hours may be considered, although routine cessation is not supported by current evidence.breastfeeding-and-medication+1

For oral mannitol used as an osmotic laxative in otherwise healthy lactating women, systemic absorption in the mother is low, and significant infant exposure through milk is unlikely; clinically relevant adverse effects in breastfed infants have not been reported.wikipedia+1
Maternal gastrointestinal side effects (abdominal discomfort, diarrhoea) may occur but do not in themselves represent a risk to the nursing infant.straightanursingstudent+1

Recommendations for use in breastfeeding

When mannitol is clearly indicated for life‑ or organ‑saving indications (e.g. intracranial hypertension, acute angle‑closure glaucoma, severe toxic ingestion requiring forced diuresis), maternal treatment should not be withheld on the basis of breastfeeding alone.drugbank+3
After a single intravenous dose, breastfeeding can usually continue without interruption, as infant exposure via milk is expected to be very low and oral absorption from the infant gut is limited.breastfeedingnetwork+1

In settings requiring repeated or high‑dose parenteral mannitol, breastfeeding decisions should be individualised, particularly in preterm or medically fragile infants, and may include monitoring for changes in feeding, stool pattern, or hydration, although clinically meaningful mannitol toxicity in this context has not been documented.accessdata.fda+3
For oral mannitol laxatives, use at the lowest effective dose and shortest duration is advised, with preference for agents with more robust lactation data when several options are clinically equivalent.bbfarma+2

Clinicians should pay special attention to maternal contraindications—such as renal failure, heart failure, pulmonary oedema, uncontrolled electrolyte disturbances, and intracranial haemorrhage—and avoid mannitol in these circumstances irrespective of lactation status.cbg-meb+4
Because mannitol may enhance urinary excretion of lithium, additional caution is warranted in nursing women treated with lithium, both for maternal stability and for established infant monitoring protocols.drugbank+1

Interaction summary (clinically relevant points)

Mannitol increases renal excretion of certain solutes; enhanced elimination of lithium has been specifically noted and may reduce serum lithium concentrations and destabilise mood control.medpedia.framar+1
Combination with other diuretics, nephrotoxic agents, or drugs that significantly affect electrolyte balance (e.g. loop diuretics, amphotericin B) can increase the risk of renal dysfunction and dysnatraemia, which indirectly may affect lactation by compromising maternal health.clevelandclinic+2
Concomitant use with agents that impair cardiac function or predispose to volume overload may increase the likelihood of pulmonary oedema and heart failure when mannitol induces rapid fluid shifts.medpedia.framar+3