OSMITROL 5% IN WATER
Clinical safety rating: caution
Comprehensive 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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for OSMITROL 5% IN WATER (OSMITROL 5% IN WATER).
| Breastfeeding | It is not known whether mannitol is excreted in human breast milk. The M/P ratio is not available. Caution is advised when administered to a nursing woman, as effects on the infant are unknown. |
| 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. |
■ FDA Black Box Warning
None.
| Serious Effects |
Anuria, severe renal impairment, pulmonary edema, active intracranial bleeding (except during craniotomy), severe dehydration, known hypersensitivity 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. |
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| 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. |