Pharmacology of Osmotic Diuretics

Mechanism of Action:

Osmotic diuretics work by increasing the osmolarity of the filtrate in the renal tubules. The glomerulus filters them but does not reabsorb them, creating an osmotic gradient that draws water into the nephron. This results in increased urine output and decreased intracranial and intraocular pressure.

Pharmacokinetics:

• Absorption: Not applicable as they are often administered intravenously.
• Distribution: Limited distribution; mainly stays in the vascular and extracellular space.
• Metabolism: No metabolism; excreted unchanged.
• Excretion: Primarily renal excretion.

Drug Examples:

• Mannitol: Most commonly used; administered intravenously.
• Isosorbide: Less commonly used; oral administration.

Clinical Use:

1. Acute Kidney Injury: To improve renal blood flow and filtration.
2. Cerebral Edema: To reduce intracranial pressure.
3. Glaucoma: To reduce intraocular pressure.
4. Drug Overdose: To increase the excretion of certain substances.

Side Effects:

• Dehydration: Due to increased urine output.
• Electrolyte Imbalance: Such as hyponatremia or hypernatremia.
• Pulmonary Edema: If used inappropriately in heart failure patients.

Drug Interactions:

• Diuretics: Increased risk of dehydration and electrolyte imbalance.
• Antihypertensives: Increased risk of hypotension.

Contraindications:

• Anuria (absence of urine production).
• Severe dehydration.
• Congestive heart failure (risk of pulmonary edema).

Understanding the pharmacology of osmotic diuretics is crucial for healthcare providers to effectively treat conditions like acute kidney injury and cerebral edema while minimizing side effects.