From the FDA Drug Label
Urea, mannitol, and aminophylline all produce significant increases in lithium excretion. Mannitol acts by increasing lithium excretion in cases of lithium toxicity.
- It is used as part of the treatment to eliminate the lithium ion from the patient.
- The mechanism is not fully detailed in the label, but it is known to produce a significant increase in lithium excretion 1.
From the Research
Mannitol is not the primary treatment for lithium toxicity, and its use should be considered cautiously, as the most recent and highest quality evidence supports hemodialysis as the preferred treatment modality for severe lithium poisoning. When considering the treatment of lithium toxicity, it's essential to prioritize the most effective and evidence-based approaches. According to the study by 2, hemodialysis is often recommended to treat lithium poisoning, and it clearly enhances the elimination of lithium. However, the same study notes that there is no evidence from randomized controlled trials to support nor refute the use of hemodialysis in the management of patients with lithium poisoning.
In terms of mannitol's mechanism of action, it can act as an osmotic diuretic to enhance lithium clearance in cases of lithium toxicity. When administered intravenously at doses of 0.5-1 g/kg, mannitol increases urine output by drawing water into the renal tubules through an osmotic gradient, which subsequently increases the excretion of lithium from the bloodstream. This approach is particularly useful in patients with impaired renal function or those who cannot tolerate aggressive hydration. Mannitol works by remaining in the extracellular compartment, creating an osmotic gradient that pulls water from tissues, including the brain, which can help reduce cerebral edema that may occur in severe lithium toxicity.
However, mannitol should be used cautiously as it can potentially cause dehydration, electrolyte imbalances, and renal failure if not properly monitored. It's also important to note that while mannitol can enhance lithium clearance, it should be used as part of a comprehensive treatment approach that includes discontinuation of lithium, adequate hydration, correction of electrolyte abnormalities, and possibly hemodialysis in severe cases with lithium levels above 4.0 mEq/L or in patients with significant clinical symptoms. The study by 3 highlights the effectiveness of high-volume continuous venovenous hemofiltration (HV-CVVH) in treating severe lithium intoxication, which may be considered as an alternative to hemodialysis in certain cases.
Key considerations in the treatment of lithium toxicity include:
- Discontinuation of lithium
- Adequate hydration
- Correction of electrolyte abnormalities
- Hemodialysis in severe cases with lithium levels above 4.0 mEq/L or in patients with significant clinical symptoms
- Potential use of mannitol as an adjunctive treatment, but with caution and close monitoring.