[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Osmotic diuretics](https://durgical.com/en/pharmacology/classes/osmotic-diuretics/) › Mannitol

[Pharmacology](https://durgical.com/en/pharmacology/) · [Osmotic diuretics](https://durgical.com/en/pharmacology/classes/osmotic-diuretics/)

# Mannitol

A sugar alcohol given by IV infusion that draws water out of the brain and eye. Used for raised intracranial and intraocular pressure.

Updated 2026-11-01

- Class: [Osmotic diuretics](https://durgical.com/en/pharmacology/classes/osmotic-diuretics/)
- Target: No protein target: osmotic effect in plasma and tubular fluid
- ATC code: B05BC01
- WHO Model List of Essential Medicines

## ⚠ High-alert medication

An error with this medicine can cause serious harm: double checks and protocols are used.

## Mechanism of action

Mannitol stays outside cells and in the blood it raises osmolality, pulling water out of brain tissue and the eye into the plasma. The glomerulus filters it freely and the tubule barely reabsorbs it, so it holds water in the lumen and causes an osmotic diuresis with loss of water and some sodium.

- Mannitol raises plasma osmolality
- Water moves from brain and eye into the blood
- Filtered mannitol holds water in the tubule
- Osmotic diuresis; intracranial and eye pressure fall

## Pharmacokinetics

**Absorption**
Given IV only for these uses (it is not absorbed well by mouth)

**Distribution**
Stays mainly in the extracellular fluid

**Metabolism**
Only a small amount is metabolised

**Elimination**
Filtered by the glomeruli and excreted unchanged in the urine

**Half-life**
About half an hour to 2.5 hours with normal kidneys; around 36 hours in kidney failure

## Indications

- Raised intracranial pressure and cerebral oedema [Traumatic brain injury →](https://durgical.com/en/conditions/traumatic-brain-injury/)
- Raised intraocular pressure, for example before eye surgery or in acute angle-closure glaucoma [Acute angle-closure glaucoma →](https://durgical.com/en/conditions/acute-angle-closure-glaucoma/)

## Adverse effects

### Common

- Fluid and electrolyte imbalance: high or low sodium and potassium
- Headache, nausea, dizziness
- Phlebitis at the infusion site
- Thirst and dehydration

### Serious (rare, important)

- Acute kidney injury (osmotic nephrosis), mainly at high doses or with nephrotoxic drugs
- Pulmonary oedema and worsened heart failure from early volume expansion
- CNS toxicity: confusion, seizures, coma; rebound rise of intracranial pressure
- Compartment syndrome after extravasation
- Hypersensitivity reactions

## Contraindications

- Anuria
- Severe hypovolaemia
- Active intracranial bleeding, except during craniotomy
- Hypersensitivity to mannitol

## Key interactions

**Nephrotoxic drugs or other diuretics**
Higher risk of kidney failure

**Neurotoxic drugs**
More CNS toxicity

**Lithium**
Risk of lithium toxicity; levels need close monitoring

**Drugs sensitive to potassium changes (e.g. digoxin)**
Arrhythmias if potassium shifts

## What is monitored

- Serum osmolality and sodium
- Potassium and kidney function
- Urine output
- Heart and lung status (signs of fluid overload)
- Neurological status and intracranial pressure

## Administration and safety

- IV infusion only, preferably through a central line: the hypertonic solution irritates peripheral veins and extravasation can cause compartment syndrome.
- Use an administration set with an in-line filter, because crystals can form.
- Inspect before use: crystals appear in the cold; follow the product's warming instructions and give only a clear solution.
- Do not give through the same set as blood products, and do not transfer to PVC bags (a precipitate can form).
- Before starting, check kidney, heart and lung status and correct fluid and electrolyte problems.

## Nursing care

- Measure urine output closely (often with a urinary catheter); report low urine output.
- Check serum osmolality, sodium and potassium as ordered during therapy.
- Watch for fluid overload: breathlessness, crackles, rising pressure.
- Monitor neurological status and watch for rebound of intracranial pressure hours later.
- Check the infusion site often for redness, swelling or leakage.

## Pregnancy and breastfeeding

Used only when the benefit clearly outweighs the risk; data in pregnancy are limited.

## Memory aid

Mannitol is a «water magnet»: it pulls water from the brain into the blood and drags it out in the urine; in a weak heart the magnet floods the lungs.

## Test yourself

Think of the answer, then tap the question to see it.

## How does mannitol cause diuresis?

It is filtered by the glomerulus and not reabsorbed, so it holds water in the tubule lumen by osmosis.

## Why is mannitol given with a filter?

Mannitol solutions can form crystals, especially in the cold, and the filter keeps crystals out of the vein.

## What can happen if mannitol leaks out of the vein?

Local irritation and swelling and, in severe cases, compartment syndrome.

## Can you name two contraindications of mannitol?

Anuria and severe hypovolaemia; also active intracranial bleeding outside a craniotomy.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/mannitol/)

## Related drugs

- [Acetazolamide](https://durgical.com/en/pharmacology/acetazolamide/)
- [Furosemide](https://durgical.com/en/pharmacology/furosemide/)

## Related conditions

- [Traumatic brain injury](https://durgical.com/en/conditions/traumatic-brain-injury/)
- [Acute angle-closure glaucoma](https://durgical.com/en/conditions/acute-angle-closure-glaucoma/)

[← Back to the class: Osmotic diuretics](https://durgical.com/en/pharmacology/classes/osmotic-diuretics/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - MANNITOL injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8ad3145e-00e7-4412-b9a5-06f00f264f30) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=B05BC01) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/mannitol/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/mannitol/