From the FDA Drug Label
The likelihood of toxicity increases with increasing serum lithium levels. Serum lithium levels greater than 1.5 mEq/l carry a greater risk than lower levels. However, patients sensitive to lithium may exhibit toxic signs at serum levels below 1.5 mEq/l. Diarrhea, vomiting, drowsiness, muscular weakness and lack of coordination may be early signs of lithium toxicity, and can occur at lithium levels below 2 mEq/l. At higher levels, giddiness, ataxia, blurred vision, tinnitus and a large output of dilute urine may be seen. Serum lithium levels above 3 mEq/l may produce a complex clinical picture involving multiple organs and organ systems Serum lithium levels should not be permitted to exceed 2 mEq/l during the acute treatment phase.
Lithium Toxicity Levels:
- Mild toxicity: may occur at levels below 2 mEq/l
- Severe toxicity: levels above 3 mEq/l may produce a complex clinical picture involving multiple organs and organ systems
- Threshold for concern: levels greater than 1.5 mEq/l carry a greater risk of toxicity 1
From the Research
Introduction to Lithium Toxicity
Lithium is a medication commonly used to treat bipolar disorder and other mental health conditions. However, it has a narrow therapeutic range, and excessive levels can lead to toxicity.
Defining Lithium Toxicity
Lithium toxicity can occur at various serum levels, but it is generally observed at levels above the therapeutic range of 0.6-1.3 mmol/L 2. Mild toxicity may be seen at levels of 1.5-2.5 mEq/L, while moderate toxicity occurs at levels of 2.5-3.5 mEq/L, and severe toxicity is observed at levels above 3.5 mEq/L 2.
Clinical Presentation and Diagnosis
The diagnosis of lithium toxicity is largely clinical, and it may present with a range of gastrointestinal and neurologic signs and symptoms [(3,4)]. The diagnosis can be challenging, as serum lithium levels may not always be elevated, especially in patients on chronic therapy [(5,4)].
Treatment and Management
Treatment of lithium toxicity typically involves supportive care, such as fluid resuscitation, and may require enhanced elimination techniques, such as hemodialysis or continuous hemodiafiltration 6. The choice of treatment depends on the severity of the toxicity, the patient's clinical condition, and the availability of resources.
Key Considerations for Treatment
- Hemodialysis is highly effective in removing circulating lithium but may require repeated or prolonged treatment due to rebound effects 6.
- Continuous hemodiafiltration can increase lithium clearance and may be more widely accessible than hemodialysis 6.
- The duration of treatment and the choice of technique depend on the patient's condition and the severity of the toxicity [(6,5)].
Differentials and Caveats
When evaluating patients for lithium toxicity, it is essential to consider the following:
- Serum lithium levels may be unreliable, especially in patients on chronic therapy [(5,4)].
- Artificial elevation of serum lithium levels can occur if blood is collected in a tube containing lithium heparin 4.
- Clinical features of toxicity are more important than a single serum lithium level 5.
Conclusion
Lithium toxicity is a serious condition that requires prompt recognition and treatment. While serum lithium levels can provide some guidance, clinical presentation and diagnosis are crucial in determining the severity of the toxicity and guiding treatment. Enhanced elimination techniques, such as hemodialysis or continuous hemodiafiltration, may be necessary to manage severe cases of lithium toxicity [(2,6)].