Drug class: Kidney Function

Medically reviewed by Drugs.com on Apr 10, 2024. Written by ASHP.

Introduction

Mannitol is a diagnostic agent used to measure the glomerular filtration rate (GFR).

Uses for Mannitol (Diagnostic)

Mannitol has been used to measure the glomerular filtration rate (GFR), which is an index of renal function. Because mannitol undergoes some tubular reabsorption, the usefulness of the drug in measuring GFR is limited and inulin has generally replaced mannitol for determination of GFR.

Mannitol (Diagnostic) Dosage and Administration

Mannitol is administered by IV infusion. To measure glomerular filtration rate (GFR), one manufacturer recommends that 100 mL of a 20% solution (20 g) of mannitol be diluted with 180 mL of 0.9% sodium chloride injection, and the resulting 280 mL of solution infused at a rate of 20 mL/minute. Another source suggests that 200 mg/kg, in a 15–25% solution, be administered in 3–5 minutes.

Mannitol clearance is determined by simultaneously measuring plasma mannitol concentrations and the quantity of mannitol excreted in urine in a given time and calculating the ratio of the amount of mannitol excreted to the plasma mannitol concentration. Catheterization is performed to facilitate complete urine collection. Mannitol clearance, and therefore GFR, is calculated using the formula:

mannitol clearance = (U × V) / P

where U is the average concentration of mannitol in the urine in mg/dL, V is the average volume of urine collected per minute in mL, and P is the average concentration of mannitol in plasma in mg/dL. Normal values for mannitol clearance (and consequently GFR), corrected to a standard 1.73 m² of body surface area, average 125 mL for men and 116 mL for women.

Cautions for Mannitol (Diagnostic)

Adverse Effects

Mannitol appears to have a low incidence of adverse effects when administered in small doses as a single test dose or as a diagnostic agent.

The most serious adverse effects of mannitol when used therapeutically are fluid and electrolyte imbalance. Accumulation of mannitol resulting from inadequate urinary output or rapid administration of large doses may result in overexpansion of extracellular fluid and circulatory overload.

In a patient with a history of allergies, mannitol caused a severe allergic reaction and anaphylaxis which responded to treatment with epinephrine hydrochloride.

Precautions and Contraindications

Before mannitol is administered, the cardiovascular status of the patient should be carefully evaluated. The infusion should be stopped or slowed if central venous pressure rises or there is any other evidence of circulatory overload. Extravasation should be avoided because local edema or skin necrosis may occur.

Mannitol is contraindicated in patients with well established anuria caused by severe renal disease. The drug is also contraindicated in patients with severe pulmonary congestion, frank pulmonary edema, severe congestive heart disease, severe dehydration, metabolic edema associated with capillary fragility or membrane permeability and not caused by renal, cardiac, or hepatic disease, or active intracranial bleeding. Electrolyte-free mannitol solutions should not be given concomitantly with blood. If blood must be given simultaneously with mannitol, at least 20 mEq of sodium chloride should be added to each liter of mannitol solution to avoid pseudoagglutination.

Pregnancy and Fertility

Pregnancy

Animal reproduction studies have not been performed with mannitol. It is also not known whether mannitol can cause fetal harm when administered to pregnant women. Mannitol should be used during pregnancy only when clearly needed.

Fertility

It is not known whether mannitol affects fertility in humans.

Pharmacology

The use of mannitol in measuring glomerular filtration rate (GFR) is not based on its pharmacologic effects, but on its elimination from the body. Mannitol has an osmotic diuretic effect and is used therapeutically for that purpose.

Mannitol (Diagnostic) Pharmacokinetics

When administered IV, mannitol remains confined to the extracellular compartment and is metabolized only very slightly, if at all, to glycogen in the liver. The drug is freely filtered by the glomeruli, with less than 10% tubular reabsorption; it is not secreted by tubular cells. Renal clearance of mannitol is slightly less than that of inulin. The elimination half-life of mannitol in adults is about 100 minutes. Approximately 80% of a 100-g dose of mannitol is excreted unchanged in urine within 3 hours.

In the presence of renal disease in which glomerular function is impaired or in conditions which impair small vessel circulation, such as congestive heart failure, cirrhosis with ascitic accumulation, shock, or dehydration, the glomerular filtration rate (GFR) and mannitol clearance values are lower than normal.

Chemistry and Stability

Chemistry

Mannitol is a hexahydroxy alcohol chemically related to mannose. Mannitol occurs as a white, crystalline powder or free-flowing granules with a sweet taste. The drug is very slightly soluble in alcohol and has a solubility of approximately 182 mg/mL in water at 25°C. Commercially available mannitol injections have a pH of 4.5–7.

Stability

Mannitol solutions should be stored at 15–30°C, and protected from freezing.

Solutions of mannitol are chemically stable but, in concentrations of 15% and more, mannitol may crystallize when exposed to low temperatures. If crystallization occurs, the mannitol solution should be autoclaved or warmed by immersing the container in hot water (approximately 60°C) and periodically shaking vigorously. The solution should be cooled to body temperature before administration. If all crystals cannot be completely dissolved, the solution should not be used. The addition of potassium or sodium chloride to mannitol solutions of 20% concentration or greater may cause precipitation of mannitol.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Medical Disclaimer