Mannitol & Osmotic Agents for IOP Reduction – Mechanism & Dosing Guide

👁 Mannitol & Osmotic Agents for IOP Reduction – Mechanism & Dosing Guide

Osmotic agents reduce intraocular pressure (IOP) by drawing water out of the eye via osmotic gradients.
Mannitol, given intravenously, is the most widely used agent in acute settings.

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💊 Mechanism Overview

1. Diuretic effect
   • Mannitol is filtered by the kidney
   • Causes fluid shift from blood to urine → strong diuresis
2. IOP-lowering effect
   • Mannitol raises serum osmolality
   • Pulls fluid from the vitreous and aqueous into the blood
   • ↓ Vitreous volume → ↓ IOP

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📐 Dosing Table

Weight (kg)Max Dose 15% Mannitol (ml)Max Dose 20% Mannitol (ml)

50	650	500
75	1000	750
100	1300	1000

• Max: 2 g/kg IV infusion
• Caution in cardiac & renal impairment

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🥄 Oral Osmotic Agents

DrugConc.DoseNote

Glycerol	50%	1.5 g/kg	High-calorie – use caution in diabetes
Isosorbide	50%	1.5 g/kg	No calorie concern – but very sweet

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✅ Summary

• Mannitol is used in emergency IOP control, especially
  for acute angle-closure attacks and preoperative IOP reduction
• Proper dosing & patient selection are crucial