OSMITROL 5% IN WATER
Clinical safety rating
cautionComprehensive clinical and safety monograph for OSMITROL 5% IN WATER (OSMITROL 5% IN WATER).
Osmotic diuretic that increases plasma osmolality, drawing water from intracellular and interstitial spaces into the extracellular compartment, thereby reducing cerebral edema and intraocular pressure; also promotes diuresis by increasing renal tubular fluid osmolality.
| Metabolism | Not metabolized; excreted unchanged by the kidneys via glomerular filtration; minimal tubular reabsorption. |
| Excretion | Primarily renal (90-100% unchanged in urine); negligible biliary or fecal elimination. |
| Half-life | Approximately 0.25-1.5 hours (15-90 minutes); prolonged in renal impairment or with mannitol accumulation (e.g., in anuria). |
| Protein binding | Negligible (<1%); not bound to plasma proteins. |
| Volume of Distribution | 0.4-0.6 L/kg; distributes primarily in extracellular fluid (ECF) with ~55% of Vd in ECF; higher in dehydration or hypovolemia. |
| Bioavailability | Not applicable (administered intravenously); oral bioavailability is <10% due to poor absorption and osmotic diarrhea. |
| Onset of Action | Intravenous: Reduction in intracranial pressure within 15 minutes; diuresis within 1-3 hours. |
| Duration of Action | Intravenous: Reduction in intracranial pressure persists for 3-8 hours; diuresis lasts 1-3 hours; effects diminish upon drug elimination. |
| Molecular Weight | 182.17 |
50-100 g intravenously as a 5% solution over 30-60 minutes; may repeat every 6-8 hours as needed. Maximum dose: 200 g in 24 hours.
| Dosage form | INJECTABLE |
| Renal impairment | Contraindicated in anuria, severe renal impairment (GFR < 10 mL/min). For GFR 10-50 mL/min: reduce dose by 50% and monitor serum osmolarity and renal function closely. |
| Liver impairment | No specific Child-Pugh based dose adjustments; use with caution in severe hepatic impairment due to risk of fluid overload and electrolyte disturbances. Monitor serum sodium and osmolarity. |
| Pediatric use | 0.25-1 g/kg/dose intravenously as a 15-20% solution (or 5-10% solution) over 2-6 hours; may repeat every 6-8 hours. Maximum dose: 2 g/kg in 24 hours. |
| Geriatric use | Use lower initial doses (25-50 g) and monitor renal function, fluid balance, and electrolytes closely due to age-related decline in renal function and increased risk of fluid overload. |
| 1st trimester | Osmotic diuretics like mannitol may cause fetal dehydration and electrolyte imbalances; use only if clearly needed. |
| 2nd trimester | Potential for fetal electrolyte disturbances; monitor maternal fluid and electrolyte status closely. |
| 3rd trimester | May cause polyhydramnios or fetal dehydration; avoid prolonged use near term. |
Clinical note
Comprehensive clinical and safety monograph for OSMITROL 5% IN WATER (OSMITROL 5% IN WATER).
| Placental transfer | Mannitol crosses the placenta via passive diffusion; fetal serum levels may reach 50-100% of maternal levels. |
| Breastfeeding | Mannitol is excreted into breast milk in small amounts; however, oral bioavailability is low. Monitor infant for gastrointestinal effects if administered intravenously to mother. |
| Lactation Rating | L3: Moderately Safe |
| Teratogenic Risk | Osmitrol 5% in Water is an osmotic diuretic. There are no adequate and well-controlled studies in pregnant women. Animal reproduction studies have not been conducted. Fetal risk cannot be ruled out; potential risks in all trimesters include electrolyte imbalances and dehydration in the mother that could affect fetal homeostasis. Use only if clearly needed and potential benefit justifies risk. |
| Fetal Monitoring | Monitor maternal vital signs, fluid balance, serum electrolytes (especially sodium and potassium), and renal function. Assess for signs of dehydration, electrolyte imbalance, and pulmonary edema. In the fetus, monitor heart rate and consider ultrasound for fluid status if prolonged therapy. |
| Fertility Effects | No studies on fertility effects in humans. Animal studies are not available. Potential impact on fertility is unknown; however, osmotic diuresis could theoretically affect gonadal function. |
■ FDA Black Box Warning
None.
| Serious Effects |
Anuria due to severe renal diseaseSevere dehydrationIntracranial hemorrhage (active)Severe pulmonary edema or congestionHypersensitivity to mannitol
| Precautions | May cause fluid and electrolyte imbalance; monitor serum sodium, potassium, and osmolarity; use with caution in patients with impaired renal function, heart failure, or pulmonary congestion; avoid extravasation (causes tissue necrosis); rapid infusion may precipitate cardiovascular overload. |
| Food/Dietary | No specific food interactions; however, adequate hydration is recommended to prevent dehydration from osmotic diuresis. High-sodium foods may exacerbate electrolyte imbalances. |
| Clinical Pearls | Osmotrol 5% in water (mannitol 5%) is a hyperosmolar agent used to reduce intracranial pressure and cerebral edema. Ensure adequate renal function before administration; monitor urine output closely to avoid osmotic diuresis-induced volume depletion. Use with caution in patients with heart failure or pulmonary congestion. Administer via IV infusion with a filter to prevent crystallization. Initiate at a dose of 0.25-1 g/kg over 30-60 minutes; redosing based on serum osmolarity (target 310-320 mOsm/L). Monitor serum sodium, potassium, and osmolarity; avoid overcorrection of hyponatremia. Rebound cerebral edema can occur upon discontinuation. |
| Patient Advice | This medication is given intravenously to reduce pressure in your brain. · You may urinate more frequently due to its diuretic effect. · Tell your doctor if you have heart failure, kidney disease, or lung problems. · Report symptoms of dehydration such as dry mouth, thirst, or dizziness. · Regular blood tests will be needed to monitor your kidney function and electrolyte levels. · Inform your healthcare provider if you experience headache, nausea, or vision changes. |
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