MANNITOL 20%
Clinical safety rating
safeAnimal studies have demonstrated safety
Increases plasma osmolality, drawing water from intracellular and interstitial spaces into the extracellular fluid, thereby reducing intracranial pressure and promoting diuresis.
| Metabolism | Minimal hepatic metabolism; primarily excreted unchanged by the kidneys. |
| Excretion | Renal, >90% unchanged by glomerular filtration; negligible biliary (<2%) or fecal elimination. |
| Half-life | Terminal elimination half-life 1.1–1.6 hours in normal renal function; prolonged to 18–36 hours in anuria/end-stage renal disease. |
| Protein binding | Negligible (<0.1%); does not bind significantly to plasma proteins. |
| Volume of Distribution | 0.25–0.4 L/kg; corresponds to extracellular fluid volume; increased in dehydration, decreased in hypervolemia. |
| Bioavailability | Intravenous: 100%; oral: <10% (non-absorbed, acts as osmotic laxative). |
| Onset of Action | Intravenous: 30–60 minutes for diuresis; 15–30 minutes for reduction of intracranial pressure. |
| Duration of Action | Diuresis: 2–4 hours; reduction of intracranial pressure: 4–6 hours. |
| Molecular Weight | 182.17 |
Adult: 50-100 g intravenously as a 20% solution over 30-60 minutes. For cerebral edema: 0.25-1 g/kg IV over 30-60 minutes. For oliguric acute kidney injury: test dose 0.2 g/kg IV over 3-5 minutes.
| Dosage form | INJECTABLE |
| Renal impairment | GFR < 50 mL/min: avoid use due to risk of volume overload and hyperosmolality. GFR 50-80 mL/min: use with caution, monitor serum osmolarity. No specific dose reduction established. |
| Liver impairment | No adjustment required for Child-Pugh class A or B. Child-Pugh class C: use with caution due to potential fluid and electrolyte imbalances; monitor closely. |
| Pediatric use | For cerebral edema: 0.25-1 g/kg IV as a 20% solution over 30-60 minutes. For elevated intracranial pressure: 0.25-0.5 g/kg IV. Maximum single dose typically 2 g/kg. |
| Geriatric use | Elderly patients: lower initial doses (e.g., 25-50 g) recommended due to decreased renal function and higher risk of electrolyte disturbances. Monitor serum osmolarity and renal function closely. |
| 1st trimester | Mannitol is pregnancy category C. Animal studies have shown adverse effects, but no adequate human studies. Use only if clearly needed. |
| 2nd trimester | Same as t1. May be used for acute reduction of intracranial pressure or for acute renal failure management when benefits outweigh risks. |
| 3rd trimester | Same as t1. Use caution near term due to potential for osmotic diuresis in the fetus. |
Clinical note
Other diuretics may have additive effects Can cause fluid and electrolyte imbalances and pulmonary congestion.
| Placental transfer | Crosses the placenta; achieves fetal concentrations similar to maternal. Used for fetal volume reduction in hydrops. |
| Breastfeeding | Mannitol is excreted into breast milk in small amounts, but systemic absorption by the infant is minimal. Use with caution; consider risk-benefit. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Mannitol is not teratogenic in animal studies. In human pregnancy, there are no controlled studies; FDA pregnancy category C. First trimester: theoretical risk due to osmotic shifts, but no documented fetal harm. Second and third trimesters: use only if clearly needed; may cause maternal dehydration and electrolyte disturbances, potentially affecting fetal fluid balance. Avoid in severe maternal renal impairment. |
| Fetal Monitoring | Monitor maternal vital signs, urine output, serum electrolytes (especially sodium and potassium), and osmolality. Assess fluid balance to avoid dehydration or fluid overload. Fetal monitoring: Non-stress test or biophysical profile if used in severe preeclampsia or during labor. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at therapeutic doses. |
■ FDA Black Box Warning
None
| Common Effects | edema |
| Serious Effects |
Anuria due to severe renal diseaseSevere dehydrationActive intracranial bleeding (except during craniotomy)Severe pulmonary edema or congestion
| Precautions | May cause volume expansion, electrolyte imbalances, and renal impairment; monitor serum electrolytes, osmolality, and renal function; use with caution in patients with heart failure or pulmonary congestion. |
| Food/Dietary | No known food interactions; however, monitor fluid and electrolyte balance as mannitol induces diuresis. |
| Clinical Pearls | Monitor serum osmolarity and sodium levels frequently; avoid use in patients with anuria, severe pulmonary congestion, or intracranial hemorrhage. Mannitol may cause acute kidney injury if used in high doses or in patients with pre-existing renal impairment. Administer via in-line filter to prevent crystallization. |
| Patient Advice | This medication is given intravenously to reduce swelling in the brain or to promote urine output. · Report any signs of allergic reaction, chest tightness, or difficulty breathing immediately. · You may experience increased thirst, headache, or nausea during infusion. · Inform your healthcare provider if you have kidney problems, heart failure, or are pregnant. |
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