Manitol: spelling variant of the osmotic diuretic mannitol
Manitol is a common spelling variant of the correct name mannitol. Both terms refer to the same sugar alcohol used medically as an osmotic diuretic, intracranial pressure agent and in inhaled cystic fibrosis therapy. Mannitol is naturally found in many plants, algae and fungi.
In clinical practice mannitol is mainly available as 10 % or 20 % intravenous solution. Use occurs in emergency medicine, neurosurgery, ophthalmology and anaesthesia. An inhaled formulation (Bronchitol) is used in CF therapy.
Mechanism of action
Mannitol is an osmotically active sugar alcohol that is barely metabolised, freely filtered renally and not reabsorbed in the tubule. From this arise the following effects:
- Osmotic diuresis: increased osmolarity in the tubule draws water into the lumen, leading to increased excretion of water, sodium and chloride
- Reduction of intracranial pressure: increased plasma osmolarity draws fluid out of brain tissue into vessels, intracranial pressure falls
- Reduction of intraocular pressure: similar to the brain, especially in acute glaucoma attack
- Inhalation in CF: osmotic effect draws water into bronchial secretion, improves mucociliary clearance
The effect appears within 15 to 30 minutes of intravenous administration and lasts 2 to 6 hours.
Indications
- Cerebral oedema and raised intracranial pressure: after stroke, traumatic brain injury, intracranial tumours
- Acute glaucoma attack: rapid lowering of intraocular pressure before surgical management
- Acute renal insufficiency: in some protocols as forced diuresis; clinical relevance now controversial, mainly historical
- Poisoning: forcing renal excretion of water-soluble toxins
- Cystic fibrosis: inhalation to improve mucociliary clearance (Bronchitol)
- Preparation for urological procedures: as irrigation solution in transurethral resection of the prostate (TURP); largely replaced by alternative fluids today
Dosing and administration
Cerebral oedema or raised intracranial pressure: 0.25 to 1 g per kg body weight intravenously as bolus or short infusion over 15 to 30 minutes. Repeat every 4 to 6 hours if clinically required.
Acute glaucoma attack: 1.5 to 2 g per kg intravenously over 30 minutes as emergency therapy.
Bronchitol inhalation in CF: 400 mg twice daily via a special dry powder inhaler, after prior tolerance test.
Use: via central venous or large-bore peripheral access, since the hyperosmolar solution can cause vein irritation. Close monitoring of electrolytes, volume status, renal function and osmolality.
Side effects
Common: polyuria, thirst, dry mouth, nausea, vomiting, headache, local irritation at injection site.
Uncommon: electrolyte disturbances (hyponatraemia or hypernatraemia, hypokalaemia), hypotension or hypertension, tachycardia, visual disturbance, dizziness.
Rare and very rare: acute renal failure with high-dose therapy, hypervolaemia up to pulmonary oedema, intracranial rebound hypertension after discontinuation, anaphylactoid reactions, seizures, crystallisation in solution from too cold storage.
Bronchitol inhalation: cough, bronchospasm, sore throat, rarely haemoptysis. Tolerance test with spirometry before first use.
Important points:
- Close monitoring of volume, electrolytes, renal function
- Contraindicated in anuria or severe decompensated heart failure
- Rebound cerebral oedema possible after discontinuation, especially with prolonged use
Interactions
- Other diuretics: additive effect on water and electrolytes
- Nephrotoxic substances (aminoglycosides, cisplatin, ciclosporin): increased risk of renal damage
- Lithium: accelerated lithium excretion, level fall
- Anticoagulants and diuretics: potentiated diuresis and hypotension
- Glycosides (digoxin): increased risk of toxicity with hypokalaemia
Special considerations
Pregnancy: possible with clear indication and under strict medical supervision. Data limited.
Breastfeeding: usually unproblematic with short-term use.
Contraindications: anuria not from reversible causes, severe heart failure with pulmonary oedema, intracranial bleeding except in surgical preparation, severe dehydration.
Storage: mannitol solutions can crystallise on cooling. Inspect visually before use, warm and filter if needed. Never infuse solutions with visible crystals.
Inhalation: Bronchitol requires a tolerance test with spirometry before first use, since some patients develop bronchospasm.
Patient communication: intravenous use is usually in a clinical setting under close monitoring. Patients on Bronchitol inhalation should be counselled on inhaler technique, possible irritation and inhaler hygiene.
Related substances
- Mannitol, correct spelling of the same substance
- Aztreonam, inhaled antibiotic in CF
- Etomidate, hypnotic in emergency medicine
- Sevoflurane, volatile anaesthetic
Frequently asked questions
Manitol or mannitol?
The correct name is mannitol with two n's. Manitol is a common spelling variant. Both refer to the same sugar alcohol with identical pharmacological properties.
How quickly does mannitol lower intracranial pressure?
Within 15 to 30 minutes of intravenous administration the intracranial pressure falls markedly. The effect lasts about 2 to 6 hours. Close monitoring of pressure, volume and electrolytes is mandatory.
What is rebound cerebral oedema?
With prolonged use mannitol can cross the blood-brain barrier into brain tissue and induce reverse osmosis after end of therapy, leading to recurrent cerebral oedema. This risk is clinically relevant and influences therapy duration.
How does mannitol help in cystic fibrosis?
Inhaled mannitol creates an osmotic gradient in the bronchi. Water is drawn into the viscous mucus secretion, which becomes thinner and easier to cough up. Mucociliary clearance improves, which can stabilise lung function long term.
Sources
- EMA European Medicines Agency
- BfArM Federal Institute for Drugs and Medical Devices
- AWMF guidelines traumatic brain injury and CF
- Gelbe Liste mannitol monograph
Legal notice and disclaimer
The information on this page is provided for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. Medicines should only be used after a doctor's prescription or pharmacy supply. All information is based on summaries of product characteristics and accepted scientific sources at the time of writing; the current SmPC of the manufacturer is always decisive. Sanoliste accepts no liability for completeness, timeliness or accuracy. In a medical emergency, dial the emergency number 112.