MANNITOL 5%
Clinical safety rating
safeOther diuretics may have additive effects Can cause fluid and electrolyte imbalances and pulmonary congestion.
Mannitol is an osmotic diuretic that increases plasma osmolality, drawing water from intracellular spaces into the extracellular fluid and vasculature, thereby reducing intracranial and intraocular pressure. It also increases renal tubular osmotic pressure, inhibiting water reabsorption and promoting diuresis.
| Metabolism | Mannitol is not metabolized in the body; it is excreted unchanged in the urine via glomerular filtration. A small amount may be reabsorbed in the proximal tubule. |
| Excretion | Renal: 90% unchanged; biliary/fecal: negligible (<2%) |
| Half-life | Terminal: 0.25–1.5 h (prolonged in renal impairment); clinical context: accumulates in renal failure, monitor serum osmolarity and renal function |
| Protein binding | <0.1% (albumin; clinically negligible) |
| Volume of Distribution | 0.3–0.6 L/kg (confined to extracellular fluid; does not cross cell membranes readily) |
| Bioavailability | IV: 100%; oral: poorly absorbed (≈5%) |
| Onset of Action | IV: diuresis within 1–3 h; infusion: osmotic effect within 15–30 minutes |
| Duration of Action | IV: 2–6 h (diuresis); clinical notes: effect terminates upon infusion cessation; longer duration in renal impairment |
| Molecular Weight | 182.17 |
Intravenous infusion of 50-100 g (as a 5% solution) over 2-6 hours, typically 500-1000 mL, for osmotic diuresis; or for reduction of intracranial pressure, 1-2 g/kg IV over 30-60 minutes as a 15-25% solution.
| Dosage form | INJECTABLE |
| Renal impairment | Contraindicated in anuria, severe renal impairment (GFR < 20 mL/min). For GFR 20-50 mL/min, reduce dose by 50% and monitor serum osmolality. |
| Liver impairment | No specific Child-Pugh based adjustments; use with caution in hepatic failure due to potential fluid overload and encephalopathy. |
| Pediatric use | For osmotic diuresis, 2 g/kg or 60 g/m² IV over 2-6 hours as a 5-10% solution; for intracranial pressure reduction, 0.25-1 g/kg IV over 30-60 minutes as a 15-25% solution. |
| Geriatric use | Start at lower end of dosing range due to increased risk of volume overload, electrolyte disturbances, and renal impairment; monitor fluid status and renal function closely. |
| 1st trimester | Mannitol is a category C drug. It should be used only if clearly needed. Limited data; risks cannot be ruled out. |
| 2nd trimester | Mannitol is a category C drug. It should be used only if clearly needed. Limited data; risks cannot be ruled out. |
| 3rd trimester | Mannitol can cause fetal fluid and electrolyte disturbances. Use only if potential benefit justifies potential risk. |
Clinical note
Other diuretics may have additive effects Can cause fluid and electrolyte imbalances and pulmonary congestion.
| FDA category | Animal |
| Placental transfer | Mannitol crosses the placenta. It is distributed in fetal tissues and amniotic fluid. Used to assess placental function. |
| Breastfeeding | Mannitol is poorly absorbed orally. It is unlikely to enter breast milk in significant amounts. However, caution is advised due to potential osmotic effects in the infant. Manufacturer recommends caution. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Mannitol 5% is not known to be teratogenic in humans. Animal studies have not shown fetal harm, but adequate human studies in pregnant women are lacking. Use during pregnancy only if clearly needed. |
| Fetal Monitoring | Monitor serum electrolytes, renal function, urine output, and signs of fluid overload (e.g., pulmonary congestion) in the mother. Fetal heart rate monitoring may be considered during administration for acute indications. |
| Fertility Effects | No data available on effects of mannitol on human fertility. Animal studies have not reported adverse fertility effects. |
■ FDA Black Box Warning
None
| Common Effects | edema |
| Serious Effects |
Anuria due to severe renal diseaseSevere pulmonary congestion or edemaActive intracranial bleeding (except during craniotomy)Severe dehydrationHypersensitivity to mannitolSevere congestive heart failure
| Precautions | Monitor serum electrolytes and renal function; osmotic nephrosis may occur with high doses or prolonged use., Use cautiously in patients with congestive heart failure, pulmonary edema, or severe dehydration due to risk of circulatory overload., May cause electrolyte imbalances (hyponatremia, hyperkalemia) and fluid shifts leading to pulmonary edema., Extravasation risk - avoid infiltration during IV administration., Not recommended for active intracranial hemorrhage (unless during craniotomy) due to risk of rebleeding. |
| Food/Dietary | No specific food interactions. Maintain adequate hydration unless contraindicated (e.g., in cases of fluid overload). |
| Clinical Pearls | Mannitol 5% is an osmotic diuretic used to reduce intracranial pressure and cerebral edema. Administer via IV infusion using an in-line filter due to risk of crystallization. Monitor serum osmolarity closely; avoid if >320 mOsm/L. Ensure adequate urine output to prevent acute kidney injury. Do NOT co-administer with blood products due to risk of red cell agglutination. |
| Patient Advice | This medication increases urination; you may need to use the bathroom frequently. · Report any signs of allergic reaction, such as rash, itching, or difficulty breathing. · Tell your healthcare provider if you have heart or kidney problems before receiving this drug. · You may experience headache, nausea, or blurred vision during infusion. · Do not stop this medication abruptly without consulting your doctor. |
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